DRAFT OF SEPTEMBER 17, 1999

ADVANCED ENERGY INDUSTRIES, INC.

COMMON STOCK, $0.001 PAR VALUE

September __, 1999

Goldman, Sachs & Co.,
BancBoston Robertson Stephens
and CIBC World Markets
c/o Goldman, Sachs & Co.
85 Broad Street
New York, New York 10004

Ladies and Gentlemen:

Advanced Energy Industries, Inc., a Delaware corporation (the "Company"), proposes, subject to the terms and conditions stated herein, to issue and sell to Goldman, Sachs & Co., BancBoston Robertson Stephens and CIBC World Markets (the "Underwriters"), an aggregate of _________ shares of the common stock, $0.001 par value of the Company ("Stock") and the stockholders of the Company named in Schedule II hereto (the "Selling Stockholders"), propose, subject to the terms and conditions stated herein, to sell to the Underwriters an aggregate of ______ shares and, at the election of the Underwriters, up to ________ additional shares of Stock. The aggregate of _________ shares to be sold by the Company and the Selling Stockholders is herein called the "Firm Shares" and the aggregate of __________ additional shares to be sold by the Selling Stockholders is herein called the "Optional Shares". The Firm Shares and the Optional Shares which the Underwriters elect to purchase pursuant to Section 2 hereof are herein collectively called the "Shares."

1. (a) The Company and each of the Selling Stockholders represents and warrants to, and agrees with, each of the Underwriters that:

(i) A registration statement on Form S-3 (File No. 33-____) (the "Initial Registration Statement") in respect of the Shares has been filed with the Securities and Exchange Commission (the "Commission"); the Initial Registration Statement and any post-effective amendment thereto, excluding exhibits thereto but including all documents incorporated by reference in the prospectus contained therein, each in the form heretofore delivered to you and for each of the other Underwriters, have been declared effective by the Commission in such form; other than a registration statement, if any, increasing the size of the offering (a "Rule 462(b) Registration Statement"), filed pursuant to Rule 462(b) under

the Securities Act of 1933, as amended (the "Act"), which became effective upon filing, no other document with respect to the Initial Registration Statement or document incorporated by reference therein has been filed with the Commission; and no stop order suspending the effectiveness of the Initial Registration Statement, any post-effective amendment thereto or the Rule 462(b) Registration Statement, if any, has been issued and no proceeding for that purpose has been initiated or threatened by the Commission (any preliminary prospectus included in the Initial Registration Statement or filed with the Commission pursuant to Rule 424(a) of the rules and regulations of the Commission under the Act is hereinafter called a "Preliminary Prospectus"; the various parts of the Initial Registration Statement and the Rule 462(b) Registration Statement, if any, including all exhibits thereto and including (i) the information contained in the form of final prospectus filed with the Commission pursuant to Rule 424(b) under the Act in accordance with Section 5(a) hereof and deemed by virtue of Rule 430A under the Act to be part of the Initial Registration Statement at the time it was declared effective and (ii) the documents incorporated by reference in the prospectus contained in the Initial Registration Statement at the time such part of the Initial Registration Statement became effective, each as amended at the time such part of the Initial Registration Statement became effective or such part of the Rule 462(b) Registration Statement, if any, became or hereafter becomes effective, are hereinafter collectively called the "Registration Statement"; such final prospectus, in the form first filed pursuant to Rule 424(b) under the Act, is hereinafter called the "Prospectus"; any reference herein to any Preliminary Prospectus or the Prospectus shall be deemed to refer to and include the documents incorporated by reference therein pursuant to Item 12 of Form S-3 under the Act, as of the date of such Preliminary Prospectus or Prospectus, as the case may be; any reference to any amendment or supplement to any Preliminary Prospectus or the Prospectus shall be deemed to refer to and include any documents filed after the date of such Preliminary Prospectus or Prospectus, as the case may be, under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), and incorporated by reference in such Preliminary Prospectus or Prospectus, as the case may be; and any reference to any amendment to the Registration Statement shall be deemed to refer to and include any annual report of the Company filed pursuant to Section 13(a) or 15(d) of the Exchange Act after the effective date of the Initial Registration Statement that is incorporated by reference in the Registration Statement);

(ii) No order preventing or suspending the use of any Preliminary Prospectus has been issued by the Commission, and each Preliminary Prospectus, at the time of filing thereof, conformed in all material respects to the requirements of the Act and the rules and regulations of the Commission thereunder, and did not contain an untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading; PROVIDED, HOWEVER, that this representation and warranty shall not apply to any statements or omissions made in reliance upon and in conformity with information furnished in writing to the Company by an Underwriter through Goldman, Sachs & Co. expressly for use therein;

(iii) The documents incorporated by reference in the Prospectus, when they became effective or were filed with the Commission, as the case may be, conformed in all material respects to the requirements of the Act or the Exchange Act, as applicable, and the rules and regulations of the Commission thereunder, and none of such documents contained an untrue statement of a material fact or omitted to state a material fact required to be stated therein or necessary to make the statements therein not misleading; and any further documents so filed and incorporated by reference in the Prospectus or any further amendment or supplement thereto, when such documents become effective or are filed with the Commission, as the case may be, will conform in all material respects to the requirements of the Act or the Exchange Act, as applicable, and the rules and regulations of the Commission thereunder and will not contain an untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading; PROVIDED, HOWEVER, that this representation and warranty shall not apply to any statements or omissions made in reliance upon and in conformity with information furnished in writing to the Company by an Underwriter through Goldman, Sachs & Co. expressly for use therein;

(iv) The Registration Statement conforms, and the Prospectus and any further amendments or supplements to the Registration Statement or the Prospectus will conform, in all material respects to the requirements of the Act and the rules and regulations of the Commission thereunder and do not and will not, as of the applicable effective date of the Registration Statement and any amendment thereto and as of the applicable filing date of the Prospectus and any amendment or supplement thereto, contain an untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading; PROVIDED, HOWEVER, that this representation and warranty shall not apply to any statements or omissions made in reliance upon and in conformity with information furnished in writing to the Company by an Underwriter through Goldman, Sachs & Co. expressly for use therein;

(v) Neither the Company nor any of its subsidiaries has sustained since the date of the latest audited financial statements included or incorporated by reference in the Prospectus any loss or interference with its business from fire, explosion, flood or other calamity, whether or not covered by insurance, or from any labor dispute or court or governmental action, order or decree, except as set forth or contemplated in the Prospectus or as would not have, individually or in the aggregate, a material adverse effect on the current or future consolidated financial position, business, prospects, stockholders' equity or results of operations of the Company and its subsidiaries, taken as a whole ("Material Adverse Effect"); and, since the respective dates as of which information is given in the Registration Statement and the Prospectus, there has not been any change in the capital stock, capital lease obligations or long-term debt of the Company or any of its subsidiaries or any material adverse change, or any development involving a prospective material adverse change, in or affecting the general affairs, management, financial position, stockholders'

equity or results of operations of the Company and its subsidiaries, taken as a whole, otherwise than as set forth or contemplated in the Prospectus;

(vi) The Company and its subsidiaries have good and marketable title in fee simple to all real property and good and marketable title to all personal property owned by them, in each case free and clear of all liens, encumbrances and defects except such as are described in the Prospectus or such as do not materially affect the value of such property and do not materially interfere with the use made and proposed to be made of such property by the Company and its subsidiaries; and any real property and buildings held under lease by the Company and its subsidiaries are held by them under valid, subsisting and enforceable leases with such exceptions as are not material and do not materially interfere with the use made and proposed to be made of such property and buildings by the Company and its subsidiaries;

(vii) The Company has been duly incorporated and is validly existing as a corporation in good standing under the laws of the State of Delaware, with the corporate power and authority to own its properties and conduct its business as described in the Prospectus, and has been duly qualified as a foreign corporation for the transaction of business and is in good standing under the laws of each other jurisdiction in which it owns or leases properties or conducts any business so as to require such qualification, or is subject to no material liability or disability by reason of the failure to be so qualified or in good standing in any such jurisdiction; and each subsidiary of the Company has been duly incorporated, is validly existing as a corporation in good standing under the laws of its jurisdiction of incorporation and has been duly qualified as a foreign corporation for the transaction of business and is in good standing under the laws of each other jurisdiction in which it owns or leases properties or conducts any business so as to require such qualification, or is subject to no material liability or disability by reason of the failure to be so qualified or in good standing in any such jurisdiction;

(viii) The Company has an authorized capitalization as set forth in the Prospectus, and all of the issued shares of capital stock of the Company have been duly and validly authorized and issued, are fully paid and non-assessable and conform to the description of the Stock contained in the Prospectus; and all of the issued shares of capital stock of each subsidiary of the Company have been duly and validly authorized and issued, are fully paid and non-assessable and are owned directly or indirectly by the Company, free and clear of all liens, encumbrances, equities or claims;

(ix) The unissued Shares to be issued and sold by the Company to the Underwriters hereunder have been duly and validly authorized and, when issued and delivered against payment therefor as provided herein, will be duly and validly issued and fully paid and non-assessable and will conform in all material respects to the description of the Stock contained in the Prospectus.

(x) The issue and sale of Shares by the Company, the compliance by the Company with all of the provisions of this Agreement and the consummation of the transactions herein contemplated will not conflict with or result in a breach or violation of any of the terms or provisions of, or constitute a default under, any indenture, mortgage, deed of trust, loan agreement or other agreement or instrument to which the Company or any of its subsidiaries is a party or by which the Company or any of its subsidiaries is bound or to which any of the property or assets of the Company or any of its subsidiaries is subject, except, in each case, (A) breaches, violations or defaults which, individually or in the aggregate, would not have a Material Adverse Effect and (B) would not have an adverse effect on the Company's ability to consummate the transactions contemplated hereby; nor will such actions result in any violation of the provisions of the Certificate of Incorporation or By-laws of the Company or any statute or any order, rule or regulation of any court or governmental agency or body having jurisdiction over the Company or any of its subsidiaries or any of their properties; and no consent, approval, authorization, order, registration or qualification of or with any such court or governmental agency or body is required for the issue and sale of the Shares or the consummation by the Company of the transactions contemplated by this Agreement, except the registration under the Act of the Shares and such consents, approvals, authorizations, registrations or qualifications as may be required under state securities or Blue Sky laws in connection with the purchase and distribution of the Shares by the Underwriters;

(xi) Neither the Company nor any of its subsidiaries (A) is in violation of its Certificate of Incorporation or By-laws or (B) in default in the performance or observance of any obligation, agreement, covenant or condition contained in any indenture, mortgage, deed of trust, loan agreement, lease or other agreement or instrument to which it is a party or by which it or any of its properties may be bound, except in the case of (B) above where such default would not have a Material Adverse Effect and would not have an adverse effect on the Company's ability to consummate the transactions contemplated hereby;

(xii) The statements set forth in the Prospectus under the caption "Description of Capital Stock", insofar as they purport to constitute a summary of the terms of the Stock, under the caption "Material U.S. Federal Income Tax Consequences", and under the caption "Underwriting", insofar as they purport to describe the provisions of the laws and documents referred to therein, are accurate, complete and fair;

(xiii) Other than as set forth in the Prospectus, there are no legal or governmental proceedings pending to which the Company or any of its subsidiaries is a party or of which any property of the Company or any of its subsidiaries is the subject which, if determined adversely to the Company or any of its subsidiaries, would individually or in the aggregate have a Material Adverse Effect; and, to the best of the Company's knowledge, no such

proceedings are threatened or contemplated by governmental authorities or threatened by others;

(xiv) The Company is not and, after giving effect to the offering and sale of the Shares, will not be an "investment company" or an entity "controlled" by an "investment company", as such terms are defined in the Investment Company Act of 1940, as amended (the "Investment Company Act");

(xv) Neither the Company nor any of its affiliates does business with the government of Cuba or with any person or affiliate located in Cuba within the meaning of Section 517.075, Florida Statutes;

(xvi) Arthur Andersen LLP, who has opined as to certain financial statements of the Company and its subsidiaries, and KPMG LLP, who has opined as to certain financial statements of RF Power Products, Inc., are each independent public accountants as required by the Act and the rules and regulations of the Commission thereunder;

(xvii) The Company has reviewed its operations and that of its subsidiaries and has made reasonable inquiries of any third parties with which the Company or any of its subsidiaries has a material relationship to evaluate the extent to which the business or operations of the Company or any of its subsidiaries will be affected by the Year 2000 Problem. As a result of such review, except as specifically described in the Prospectus, the Company has no reason to believe, and does not believe, that the Year 2000 Problem will have a material adverse effect on the general affairs, management, the current or future consolidated financial position, business, prospects, stockholders' equity or results of operations of the Company and its subsidiaries or result in any material loss or interference with the Company's business or operations. The "Year 2000 Problem" as used herein means any significant risk that computer hardware, firmware or software used in the receipt, transmission, processing, manipulation, storage, retrieval, retransmission or other utilization of data or in the operation of mechanical or electrical systems of any kind will not, in the case of dates or time periods occurring after December 31, 1999, function at least as effectively as in the case of dates or time periods occurring prior to January 1, 2000; and

(xviii) Neither the Company nor any of its subsidiaries own any real property.

(b) Each of the Selling Stockholders, severally and not jointly, solely with respect to himself, represents and warrants to, and agrees with, each of the Underwriters and the Company that:

(i) All consents, approvals, authorizations and orders necessary for the execution and delivery by such Selling Stockholder of this Agreement and the Power of Attorney and the Custody Agreement hereinafter referred to, and for the sale and delivery of the Shares to be sold by such Selling Stockholder hereunder, have been obtained, except such consents,

approvals, authorizations and orders as may be required under state securities and Blue Sky laws, and such Selling Stockholder has full right, power and authority to enter into this Agreement, the Power-of-Attorney and the Custody Agreement (each is defined in clause 1(b)(viii) below) and to sell, assign, transfer and deliver the Shares to be sold by such Selling Stockholder hereunder;

(ii) The sale of the Shares to be sold by such Selling Stockholder hereunder and the compliance by such Selling Stockholder with all of the provisions of this Agreement, the Power of Attorney and the Custody Agreement and the consummation of the transactions herein and therein contemplated will not conflict with or result in a breach or violation of any of the terms or provisions of, or constitute a default under, any statute, indenture, mortgage, deed of trust, loan agreement or other agreement or instrument to which such Selling Stockholder is a party or by which such Selling Stockholder is bound or to which any of the property or assets of such Selling Stockholder is subject, except, in each case (A) breaches, violations or defaults which, individually or in the aggregate, would not have a material adverse effect on such Selling Stockholder's current or future financial position, and (B) would not have an adverse effect on such Selling Stockholder's ability to consummate the transactions contemplated hereby; nor will such action result in any violation of the provisions of or any statute or any order, rule or regulation of any court or governmental agency or body having jurisdiction over such Selling Stockholder or the property of such Selling Stockholder;

(iii) Such Selling Stockholder has, and immediately prior to each Time of Delivery (as defined in Section 4 hereof) such Selling Stockholder will have, good and valid title to the Shares to be sold by such Selling Stockholder hereunder, free and clear of all liens, encumbrances, equities or claims; and, upon delivery of such Shares and payment therefor pursuant hereto, good and valid title to such Shares, free and clear of all liens, encumbrances, equities or claims, will pass to the several Underwriters;

(iv) During the period beginning from the date of the Prospectus and continuing to and including the date 90 days after the date of the Prospectus, not to offer, sell contract to sell or otherwise dispose of, except as provided hereunder, any securities of the Company that are substantially similar to the Shares, including but not limited to any securities that are convertible into or exchangeable for, or that represent the right to receive, Stock or any such substantially similar securities (other than pursuant to employee stock option plans existing on, or upon the conversion or exchange of convertible or exchangeable securities outstanding as of, the date of this Agreement), without your prior written consent;

(v) Such Selling Stockholder has not taken and will not take, directly or indirectly, any action which is designed to or which has constituted or which might reasonably be expected to cause or result in stabilization or manipulation of the price of any security of the Company to facilitate the sale or resale of the Shares;

(vi) To the extent that any statements or omissions made in the Registration Statement, any Preliminary Prospectus, the Prospectus or any amendment or supplement thereto are made in reliance upon and in conformity with written information furnished to the Company by such Selling Stockholder expressly for use therein, such Preliminary Prospectus and the Registration Statement did, and the Prospectus and any further amendments or supplements to the Registration Statement and the Prospectus, when they become effective or are filed with the Commission, as the case may be, will conform in all material respects to the requirements of the Act and the rules and regulations of the Commission thereunder and will not contain any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary to make the statements therein not misleading;

(vii) In order to document the Underwriters' compliance with the reporting and withholding provisions of the Tax Equity and Fiscal Responsibility Act of 1982 with respect to the transactions herein contemplated, such Selling Stockholder will deliver to you prior to or at the First Time of Delivery (as hereinafter defined) a properly completed and executed United States Treasury Department Form W-9 (or other applicable form or statement specified by Treasury Department regulations in lieu thereof);

(viii) Certificates in negotiable form representing all of the Shares to be sold by such Selling Stockholder hereunder have been placed in custody under a Custody Agreement, in the form heretofore furnished to you (the "Custody Agreement"), duly executed and delivered by such Selling Stockholder to _______________, as custodian (the "Custodian"), and such Selling Stockholder has duly executed and delivered a Power of Attorney, in the form heretofore furnished to you (the "Power of Attorney"), appointing the persons indicated in Schedule II hereto, and each of them, as such Selling Stockholder's attorneys-in-fact (the "Attorneys-in-Fact") with authority to execute and deliver this Agreement on behalf of such Selling Stockholder, to determine the purchase price to be paid by the Underwriters to the Selling Stockholders as provided in Section 2 hereof, to authorize the delivery of the Shares to be sold by such Selling Stockholder hereunder and otherwise to act on behalf of such Selling Stockholder in connection with the transactions contemplated by this Agreement and the Custody Agreement; and

(ix) The Shares represented by the certificates held in custody for such Selling Stockholder under the Custody Agreement are subject to the interests of the Underwriters hereunder; the arrangements made by such Selling Stockholder for such custody, and the appointment by such Selling Stockholder of the Attorneys-in-Fact by the Power of Attorney, are to that extent irrevocable; the obligations of the Selling Stockholders hereunder shall not be terminated by operation of law, whether by the death or incapacity of any individual Selling Stockholder or, in the case of an estate or trust, by the death or incapacity of any executor or trustee or the termination of such estate or trust, or in the case of a partnership

or corporation, by the dissolution of such partnership or corporation, or by the occurrence of any other event; if any individual Selling Stockholder or any such executor or trustee should die or become incapacitated, or if any such estate or trust should be terminated, or if any such partnership or corporation should be dissolved, or if any other such event should occur, before the delivery of the Shares hereunder, certificates representing the Shares shall be delivered by or on behalf of the Selling Stockholders in accordance with the terms and conditions of this Agreement and of the Custody Agreements; and actions taken by the Attorneys-in-Fact pursuant to the Powers of Attorney shall be as valid as if such death, incapacity, termination, dissolution or other event had not occurred, regardless of whether or not the Custodian, the Attorneys-in-Fact, or any of them, shall have received notice of such death, incapacity, termination, dissolution or other event.

2. Subject to the terms and conditions herein set forth, (a) the Company agrees to issue and sell and each of the Selling Stockholders agrees, severally and not jointly, to sell to each of the Underwriters, and each of the Underwriters agrees, severally and not jointly, to purchase from the Company and each of the Selling Stockholders, at a purchase price per share of $__________, the number of Firm Shares (to be adjusted by you so as to eliminate fractional shares) determined by multiplying the aggregate number of Firm Shares to be sold by the Company and each of the Selling Stockholders as set forth opposite their respective names in Schedule II hereto by a fraction, the numerator of which is the aggregate number of Firm Shares to be purchased by such Underwriter as set forth opposite the name of such Underwriter in Schedule I hereto and the denominator of which is the aggregate number of Firm Shares to be purchased by all of the Underwriters from all of the Selling Stockholders hereunder and (b) in the event and to the extent that the Underwriters shall exercise the election to purchase Optional Shares as provided below, each of the Selling Stockholders agrees, severally and not jointly, to sell to each of the Underwriters, and each of the Underwriters agrees, severally and not jointly, to purchase from each of the Selling Stockholders, at the purchase price per share set forth in clause
(a) of this Section 2, that portion of the number of Optional Shares as to which such election shall have been exercised (to be adjusted by you so as to eliminate fractional shares) determined by multiplying such number of Optional Shares by a fraction the numerator of which is the maximum number of Optional Shares which such Underwriter is entitled to purchase as set forth opposite the name of such Underwriter in Schedule I hereto and the denominator of which is the maximum number of Optional Shares that all of the Underwriters are entitled to purchase hereunder.

The Selling Stockholders, as and to the extent indicated in Schedule II hereto, hereby grant, severally and not jointly, to the Underwriters the right to purchase at their election up to _________ Optional Shares, at the purchase price per share set forth in clause (a) of the first paragraph of this Section 2, for the sole purpose of covering sales of Shares in excess of the number of the Firm Shares. Any such election to purchase Optional Shares shall be made in proportion to the number of Optional Shares to be sold by each Selling Stockholder. Any such election to purchase Optional Shares may be exercised by written notice from you to the Attorneys-in-Fact, given within a period of 30 calendar days after the date of this Agreement, and setting forth the aggregate number of Optional Shares to be purchased and the date on which such Optional Shares are to be delivered, as

determined by you but in no event earlier than the First Time of Delivery (as defined in Section 4 hereof) or, unless you and the Attorneys-in-Fact otherwise agree in writing, earlier than two or later than ten business days after the date of such notice.

As compensation to the Underwriters for their commitments hereunder, each of the Company and the Selling Stockholders, as applicable, at each Time of Delivery (as defined in Section 4 hereof) will pay to Goldman, Sachs & Co., for the accounts of the several Underwriters, an amount equal to $__________ per share for the Shares to be delivered by the Company and the Selling Stockholders, as applicable, hereunder at such Time of Delivery.

3. Upon the authorization by you of the release of the Firm Shares, the several Underwriters propose to offer the Firm Shares for sale upon the terms and conditions set forth in the Prospectus.

4. (a) The Shares to be purchased by each Underwriter hereunder, in definitive form, and in such authorized denominations and registered in such names as Goldman, Sachs & Co. may request upon at least forty-eight hours' prior notice to the Company and the Selling Stockholders shall be delivered by or on behalf of the Company and the Selling Stockholders to Goldman, Sachs & Co., through the facilities of The Depository Trust Company ("DTC"), for the account of each Underwriter, against payment by or on behalf of such Underwriter of the purchase price therefor by wire transfer of Federal (same-day) funds to the account specified by the Company and the Custodian to Goldman, Sachs & Co. at least forty-eight hours in advance. The Company will cause the certificates representing the Shares to be made available for checking and packaging at least twenty-four hours prior to the Time of Delivery (as defined below) with respect thereto at the office of DTC or its designated custodian (the "Designated Office"). The time and date of such delivery and payment shall be, with respect to the Firm Shares, 9:30 a.m., New York time, on ____________, 1999 or such other time and date as Goldman, Sachs & Co., the Company and the Selling Stockholders may agree upon in writing, and, with respect to the Optional Shares, 9:30 a.m., New York time, on the date specified by Goldman, Sachs & Co. in the written notice given by Goldman, Sachs & Co. of the Underwriters' election to purchase such Optional Shares, or such other time and date as Goldman, Sachs & Co., the Selling Stockholders may agree upon in writing. Such time and date for delivery of the Firm Shares is herein called the "First Time of Delivery", such time and date for delivery of the Optional Shares, if not the First Time of Delivery, is herein called the "Second Time of Delivery", and each such time and date for delivery is herein called a "Time of Delivery".

At each Time of Delivery, the Company and each of the Selling Stockholders, as applicable, will pay, or cause to be paid, the commission payable at each Time of Delivery to the Underwriters under Section 2 hereof by wire transfer of Federal (same-day) funds to the account specified by Goldman, Sachs & Co.

(b) The documents to be delivered at each Time of Delivery by or on behalf of the parties hereto pursuant to Section 7 hereof, including the cross receipt for the Shares and any additional documents requested by the Underwriters pursuant to Section 7(k) hereof will be delivered

at the offices of [Kaye, Scholer, Fierman, Hays & Handler, LLP, 1999 Avenue of the Stars, Suite 1600, Los Angeles, California 90067] (the "Closing Location"), and the Shares will be delivered at the Designated Office, all at such Time of Delivery. A meeting will be held at the Closing Location at _______ p.m., New York City time, on the New York Business Day next preceding such Time of Delivery, at which meeting the final drafts of the documents to be delivered pursuant to the preceding sentence will be available for review by the parties hereto. For the purposes of this Section 4, "New York Business Day" shall mean each Monday, Tuesday, Wednesday, Thursday and Friday which is not a day on which banking institutions in New York are generally authorized or obligated by law or executive order to close.

5. The Company agrees with each of the Underwriters:

(a) To prepare the Prospectus in a form approved by you and to file such Prospectus pursuant to Rule 424(b) under the Act not later than the Commission's close of business on the second business day following the execution and delivery of this Agreement, or, if applicable, such earlier time as may be required by Rule 430A(a)(3) under the Act; to make no further amendment or any supplement to the Registration Statement or Prospectus prior to such Time of Delivery which shall be disapproved by you promptly after reasonable notice thereof; to advise you, promptly after it receives notice thereof, of the time when any amendment to the Registration Statement has been filed or becomes effective or any supplement to the Prospectus or any amended Prospectus has been filed and to furnish you with copies thereof; to file timely all reports and any definitive proxy or information statements required to be filed by the Company with the Commission pursuant to Section 13(a), 13(c), 14 or 15(d) of the Exchange Act subsequent to the date of the Prospectus and for so long as the delivery of a prospectus is required in connection with the offering or sale of the Shares; to advise you, promptly after it receives notice thereof, of the issuance by the Commission of any stop order or of any order preventing or suspending the use of any Preliminary Prospectus or prospectus, of the suspension of the qualification of the Shares for offering or sale in any jurisdiction, of the initiation or threatening of any proceeding for any such purpose, or of any request by the Commission for the amending or supplementing of the Registration Statement or Prospectus or for additional information; and, in the event of the issuance of any stop order or of any order preventing or suspending the use of any Preliminary Prospectus or prospectus or suspending any such qualification, promptly to use its best efforts to obtain the withdrawal of such order;

(b) Promptly from time to time to take such action as you may reasonably request to qualify the Shares for offering and sale under the securities laws of such jurisdictions as you may request and to comply with such laws so as to permit the continuance of sales and dealings therein in such jurisdictions for as long as may be necessary to complete the distribution of the Shares, provided that in connection therewith the Company shall not be required to qualify as a foreign corporation or to file a general consent to service of process in any jurisdiction;

(c) Prior to 10:00 a.m., New York City time, on the New York Business Day next succeeding the date of this Agreement and from time to time, to furnish the Underwriters with copies of the Prospectus in New York City in such quantities as you may reasonably request, and, if the delivery of a prospectus is required at any time prior to the expiration of nine months after the time of issue of the Prospectus in connection with the offering or sale of the Shares and if at such time any event shall have occurred as a result of which the Prospectus as then amended or supplemented would include an untrue statement of a material fact or omit to state any material fact necessary in order to make the statements therein, in light of the circumstances under which they were made when such Prospectus is delivered, not misleading, or, if for any other reason it shall be necessary during such period to amend or supplement the Prospectus or to file under the Exchange Act any document incorporated by reference in the Prospectus in order to comply with the Act or the Exchange Act, to notify you and upon your request to file such document and to prepare and furnish without charge to each Underwriter and to any dealer in securities as many copies as you may from time to time reasonably request of an amended Prospectus or a supplement to the Prospectus which will correct such statement or omission or effect such compliance, and in case any Underwriter is required to deliver a prospectus in connection with sales of any of the Shares at any time nine months or more after the time of issue of the Prospectus, upon your request but at the expense of such Underwriter, to prepare and deliver to such Underwriter as many copies as you may request of an amended or supplemented Prospectus complying with Section 10(a)(3) of the Act;

(d) To make generally available to its securityholders as soon as practicable, but in any event not later than eighteen months after the effective date of the Registration Statement (as defined in Rule 158(c) under the Act), an earnings statement of the Company and its subsidiaries (which need not be audited) complying with
Section 11(a) of the Act and the rules and regulations of the Commission thereunder (including, at the option of the Company, Rule 158);

(e) During the period beginning from the date of the Prospectus and continuing to and including the date 90 days after the date of the Prospectus, not to offer, sell, contract to sell or otherwise dispose of, except as provided hereunder, any securities of the Company that are substantially similar to the Shares, including but not limited to any securities that are convertible into or exchangeable for, or that represent the right to receive, Stock or any such substantially similar securities (other than pursuant to employee stock option plans existing on, or upon the conversion or exchange of convertible or exchangeable securities outstanding as of, the date of this Agreement and other than the ___% Convertible Subordinated Notes sold to the Underwriters pursuant to that certain Underwriting Agreement, dated the date hereof), among the Company and Goldman, Sachs & Co., Merrill Lynch, Pierce, Fenner & Smith Incorporated and Banc of America Securities LLC, without your prior written consent;

(f) To furnish to its stockholders as soon as practicable after the end of each fiscal year an annual report (including a balance sheet and statements of income, stockholders' equity and cash flows of the Company and its consolidated subsidiaries certified by independent public accountants) and, as soon as practicable after the end of each of the first three quarters of each fiscal year (beginning with the fiscal quarter ending after the effective date of the Registration Statement), to make available to its stockholders consolidated summary financial information of the Company and its subsidiaries for such quarter in reasonable detail;

(g) During a period of five years from the effective date of the Registration Statement, to furnish to you copies of all reports or other communications (financial or other) furnished to stockholders, and to deliver to you (i) as soon as they are available, copies of any reports and financial statements furnished to or filed with the Commission or any national securities exchange on which the Stock or any class of securities of the Company is listed; and (ii) such additional information concerning the business and financial condition of the Company as you may from time to time reasonably request (such financial statements to be on a consolidated basis to the extent the accounts of the Company and its subsidiaries are consolidated in reports furnished to its stockholders generally or to the Commission);

(h) To use the net proceeds received by it from the sale of the Shares pursuant to this Agreement in the manner specified in the Prospectus under the caption "Use of Proceeds";

(i) To use its best efforts to list for quotation the Shares on the National Association of Securities Dealers Automated Quotations National Market System ("NASDAQ"); and

(j) If the Company elects to rely upon Rule 462(b), the Company shall file a Rule 462(b) Registration Statement with the Commission in compliance with Rule 462(b) by 10:00 P.M., Washington, D.C. time, on the date of this Agreement, and the Company shall at the time of filing either pay to the Commission the filing fee for the Rule 462(b) Registration Statement or give irrevocable instructions for the payment of such fee pursuant to Rule 111(b) under the Act.

6. The Company and each of the Selling Stockholders covenant and agree with one another and with the several Underwriters that (a) the Company will pay or cause to be paid the following: (i) the fees, disbursements and expenses of the Company's counsel and accountants in connection with the registration of the Shares under the Act and all other expenses in connection with the preparation, printing and filing of the Registration Statement, any Preliminary Prospectus and the Prospectus and amendments and supplements thereto and the mailing and delivering of copies thereof to the Underwriters and dealers; (ii) the cost of printing or producing any Agreement among Underwriters, this Agreement, the Blue Sky Memorandum, closing documents (including

any compilations thereof) and any other documents in connection with the offering, purchase, sale and delivery of the Shares; (iii) all expenses in connection with the qualification of the Shares for offering and sale under state securities laws as provided in Section 5(b) hereof, including the fees and disbursements of counsel for the Underwriters in connection with such qualification and in connection with the Blue Sky and legal investment survey; (iv) all fees and expenses in connection with listing the Shares on the NASDAQ; (v) the filing fees incident to, and the fees and disbursements of counsel for the Underwriters in connection with, any required review by NASD Regulations, Inc. of the terms of the sale of the Shares; (vi) the cost of preparing stock certificates; (vii) the cost and charges of any transfer agent or registrar; and (viii) all other costs and expenses incident to the performance of its obligations hereunder which are not otherwise specifically provided for in this Section; and (b) such Selling Stockholder will pay or cause to be paid all costs and expenses incident to the performance of such Selling Stockholder's obligations hereunder which are not otherwise specifically provided for in this Section, including (i) any fees and expenses of counsel for such Selling Stockholder; (ii) such Selling Stockholder's pro rata share of the fees and expenses of the Attorneys-in-Fact and the Custodian; and (iii) all other costs, expenses and taxes incident to the sale and delivery of the Shares to be sold by such Selling Stockholder to the Underwriters hereunder. In connection with clause
(b)(iii) of the preceding sentence, Goldman, Sachs & Co. agrees to pay New York State stock transfer tax, and the Selling Stockholder agrees to reimburse Goldman, Sachs & Co. for associated carrying costs if such tax payment is not rebated on the day of payment and for any portion of such tax payment not rebated. It is understood, however, that the Company shall bear, and the Selling Stockholders shall not be required to pay or to reimburse the Company for, the cost of any other matters not directly relating to the sale and purchase of the Shares pursuant to this Agreement, and that, except as provided in this Section, and Sections 8 and 11 hereof, the Underwriters will pay all of their own costs and expenses, including the fees of their counsel, transfer taxes on resale of any of the Shares by them, and any advertising expenses connected with any offers they may make.

7 The obligations of the Underwriters hereunder, as to the Shares to be delivered at each Time of Delivery, shall be subject, in their discretion, to the condition that all representations and warranties and other statements of the Company and of the Selling Stockholders herein are, at and as of such Time of Delivery, true and correct, the condition that the Company and the Selling Stockholders shall have performed all of its and their obligations hereunder theretofore to be performed, and the following additional conditions:

(a) The Prospectus shall have been filed with the Commission pursuant to Rule 424(b) within the applicable time period prescribed for such filing by the rules and regulations under the Act and in accordance with Section 5(a) hereof; if the Company has elected to rely upon Rule 462(b), the Rule 462(b) Registration Statement shall have become effective by 10:00 P.M., Washington, D.C. time, on the date of this Agreement; no stop order suspending the effectiveness of the Registration Statement or any part thereof shall have been issued and no proceeding for that purpose shall have been initiated or threatened by the Commission; and all requests for additional information on the part of the Commission shall have been complied with to your reasonable satisfaction;

(b) Kaye, Scholer, Fierman, Hays & Handler, LLP, counsel for the Underwriters, shall have furnished to you such written opinion or opinions (a draft of each such opinion is attached as Annex II(a) hereto), dated such Time of Delivery, with respect to the matters covered in paragraphs (i), (ii), (vii), (xiii) and (xiv) of subsection (c) below as well as such other related matters as you may reasonably request, and such counsel shall have received such papers and information as they may reasonably request to enable them to pass upon such matters;

(c) Thelen Reid & Priest LLP, counsel for the Company, shall have furnished to you their written opinion (a draft of such opinion is attached as Annex II(b) hereto), dated such Time of Delivery, in form and substance satisfactory to you, to the effect that:

(i) The Company has been duly incorporated and is validly existing as a corporation in good standing under the laws of the State of Delaware. The Company has the corporate power and authority to own its properties and conduct its business as described in the Prospectus;

(ii) The Company has an authorized capitalization as set forth in the Prospectus, and all of the issued shares of capital stock of the Company (including the Shares being delivered at such Time of Delivery) have been duly and validly authorized and issued and are fully paid and non-assessable; and the Shares conform, in all material respects, to the description of the Stock contained in the Prospectus;

(iii) The Company is duly qualified as a foreign corporation for the transaction of business and is in good standing under the laws of each jurisdiction in which it owns or leases properties or conducts any business so as to require such qualification, except where the failure to be so qualified or in good standing would not, individually or in the aggregate, have a Material Adverse Effect (such counsel being entitled to rely in respect of the opinion in this clause upon opinions of local counsel and in respect of matters of fact upon certificates of officers of the Company, provided that such counsel shall state that they believe that both you and they are justified in relying upon such opinions and certificates);

(iv) Each subsidiary of the Company organized under the laws of the United States, any state of the United States or the District of Columbia (a "Domestic Subsidiary") has been duly incorporated and is validly existing as a corporation in good standing under the laws of its jurisdiction of incorporation; and all of the issued shares of capital stock of each Domestic Subsidiary have been duly and validly authorized and issued, are fully paid and non-assessable, and are owned directly or indirectly by the Company, free and clear of all liens, encumbrances, equities or claims (such counsel being entitled to rely in respect of the opinion in this

clause upon opinions of local counsel and in respect of matters of fact upon certificates of officers of the Company or its subsidiaries, provided that such counsel shall state that they believe that both you and they are justified in relying upon such opinions and certificates);

(v) To such counsel's knowledge, the manufacturing facilities located at 1625 Sharp Point Drive, Fort Collins, Colorado and 1007 Laurel Oak Drive, Voorhees, New Jersey, held under lease by the Company and RF Power Products, Inc. (the "Principal Subsidiary") are held by them under valid, subsisting and enforceable leases except as such enforcement may be limited by bankruptcy and with such exceptions as are not material and do not interfere with the use made and proposed to be made of such property and buildings by the Company and the Principal Subsidiary (in giving the opinion in this clause, such counsel may state that no examination of record titles for the purpose of such opinion has been made, and that they are relying upon a general review of the titles of the Company and the Principal Subsidiary, upon opinions of local counsel and abstracts, reports and policies of title companies rendered or issued at or subsequent to the time of acquisition of such property by the Company or the Principal Subsidiary, upon opinions of counsel to the lessors of such property and, in respect of matters of fact, upon certificates of officers of the Company or its subsidiaries, provided that such counsel shall state that they believe that both you and they are justified in relying upon such opinions, abstracts, reports, policies and certificates);

(vi) To the best of such counsel's knowledge and other than as set forth in the Prospectus, there are no legal or governmental proceedings pending to which the Company or any of its subsidiaries is a party or of which any property of the Company or any of its subsidiaries is the subject which, if determined adversely to the Company or any of its subsidiaries, would, individually or in the aggregate, have a Material Adverse Effect and, to the best of such counsel's knowledge, no such proceedings are threatened or contemplated by governmental authorities or threatened by others;

(vii) This Agreement has been duly authorized, executed and delivered by the Company;

(viii) The issue and sale of Shares by the Company, the compliance by the Company with all of the provisions of this Agreement and the consummation of the transactions herein contemplated will not conflict with or result in a breach or violation of any of the terms or provisions of, or constitute a default under, any indenture, mortgage, deed of trust, loan agreement or other agreement or instrument known to such counsel to which the Company or any of its subsidiaries is a party or by which the Company or any of its subsidiaries is bound or to which any of the property or assets of the Company or any of its subsidiaries is subject, except in each

case, (A) breaches, violations or defaults which, individually or in the aggregate, would not have a Material Adverse Effect and (B) would not have an adverse effect on the Company's ability to consummate the transactions contemplated hereby; nor will such actions result in any violation of the provisions of the Certificate of Incorporation or By-laws of the Company or any statute or any order, rule or regulation of any court or governmental agency or body having jurisdiction over the Company or any of its subsidiaries or any of their properties;

(ix) No consent, approval, authorization, order, registration or qualification of or with any such court or governmental agency or body is required for the issue and sale of the Shares or the consummation by the Company of the transactions contemplated by this Agreement, except such as have been obtained under the Act, and such consents, approvals, authorizations, registrations or qualifications as may be required under state securities or Blue Sky laws in connection with the purchase and distribution of the Shares by the Underwriters;

(x) Neither the Company nor any of its Domestic Subsidiaries is (A) in violation of its Certificate of Incorporation or By-laws or (B) in default in the performance or observance of any obligation, agreement, covenant or condition contained in any indenture, mortgage, deed of trust, loan agreement, lease or other agreement or instrument known to such counsel to which it is a party or by which it or any of its properties may be bound, except in the case of (B) where such default (1) would not have a Material Adverse Effect and (2) would not have an adverse effect on the Company's ability to consummate the transactions contemplated hereby (such counsel being entitled to rely in respect of the opinion in this clause upon opinions of local counsel and in respect of matters of fact upon certificates of officers of the Company or its Domestic Subsidiaries, provided that such counsel shall state that they believe that both you and they are justified in relying upon such opinions and certificates);

(xi) The statements set forth in the Prospectus under the caption "Description of Capital Stock", insofar as they purport to constitute a summary of the terms of the Stock, under the caption "Material United States Federal Income Tax Consequences", and under the caption "Underwriting", insofar as they purport to describe the provisions of the laws and documents referred to therein, are accurate, complete and fair in all material respects;

(xii) The Company is not an "investment company" or an entity "controlled" by an "investment company", as such terms are defined in the Investment Company Act;

(xiii) The documents incorporated by reference in the Prospectus or any further amendment or supplement thereto made by the Company prior to the Time of Delivery (other than the financial statements and related schedules therein, as to which such counsel need express no opinion), when they became effective or were filed with the Commission, as the case may be, complied as to form in all material respects with the requirements of the Act or the Exchange Act, as applicable and the rules and regulations of the Commission thereunder; and they have no reason to believe that any of such documents, when such documents became effective or were so filed, as the case may be, contained, in the case of a registration statement which became effective under the Act, an untrue statement of a material fact, or omitted to state a material fact required to be stated therein or necessary to make the statements therein not misleading, or, in the case of other documents which were filed under the Act or the Exchange Act with the Commission, an untrue statement of a material fact or omitted to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made when such documents were so filed, not misleading; and

(xiv) The Registration Statement and the Prospectus and any further amendments and supplements thereto made by the Company prior to such Time of Delivery (other than the financial statements and related schedules therein, as to which such counsel need express no opinion) comply as to form in all material respects with the requirements of the Act and the rules and regulations thereunder; although they do not assume any responsibility for the accuracy, completeness or fairness of the statements contained in the Registration Statement or the Prospectus, except for those referred to in the opinion in subsection (xi) of this Section 7(c), they have no reason to believe that, as of its effective date, the Registration Statement or any further amendment thereto made by the Company prior to such Time of Delivery (other than the financial statements and related schedules therein, as to which such counsel need express no opinion) contained an untrue statement of a material fact or omitted to state a material fact required to be stated therein or necessary to make the statements therein not misleading or that, as of its date, the Prospectus or any further amendment or supplement thereto made by the Company prior to such Time of Delivery (other than the financial statements and related schedules therein, as to which such counsel need express no opinion) contained an untrue statement of a material fact or omitted to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading or that, as of such Time of Delivery, either the Registration Statement or the Prospectus or any further amendment or supplement thereto made by the Company prior to such Time of Delivery (other than the financial statements and related schedules therein, as to which such counsel need express no opinion) contains an untrue statement of a material fact or omits to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading; and they do not know of any amendment to the Registration

Statement required to be filed or of any contracts or other documents of a character required to be filed as an exhibit to the Registration Statement or required to be incorporated by reference into the Prospectus or required to be described in the Registration Statement or the Prospectus which are not filed or incorporated by reference or described as required;

(d) The respective counsel for each of the Selling Stockholders, as indicated in Schedule II hereto, each shall have furnished to you their written opinion with respect to each of the Selling Stockholders for whom they are acting as counsel (a draft of each such opinion is attached as Annex II(c) hereto), dated such Time of Delivery, in form and substance satisfactory to you, to the effect that:

(i) A Power-of-Attorney and a Custody Agreement have been duly executed and delivered by such Selling Stockholder and constitute valid and binding agreements of such Selling Stockholder in accordance with their terms;

(ii) This Agreement has been duly executed and delivered by or on behalf of such Selling Stockholder; and the sale of the Shares to be sold by such Selling Stockholder hereunder and the compliance by such Selling Stockholder with all of the provisions of this Agreement, the Power-of-Attorney and the Custody Agreement and the consummation of the transactions herein and therein contemplated will not conflict with or result in a breach or violation of any terms or provisions of, or constitute a default under, any statute, indenture, mortgage, deed of trust, loan agreement or other agreement or instrument known to such counsel to which such Selling Stockholder is a party or by which such Selling Stockholder is bound or to which any of the property or assets of such Selling Stockholder is subject, except in each case, breaches, violations or defaults which, individually or in the aggregate, would not have a Material Adverse Effect and would not have an adverse effect on the Company's ability to consummate the transactions contemplated hereby, nor will such action result in any violation of the provisions of or any order, rule or regulation known to such counsel of any court or governmental agency or body having jurisdiction over such Selling Stockholder or the property of such Selling Stockholder;

(iii) No consent, approval, authorization or order of any court or governmental agency or body is required for the consummation of the transactions contemplated by this Agreement in connection with the Shares to be sold by such Selling Stockholder hereunder, except ______________ which
[HAS] [HAVE] been duly obtained and [IS] [ARE] in full force and effect, such as have been obtained under the Act and such as may be required under state securities or Blue Sky laws in connection with the purchase and distribution of such Shares by the Underwriters;

(iv) Immediately prior to such Time of Delivery, to such counsel's knowledge, such Selling Stockholder has full right, power and authority to sell, assign, transfer and deliver the Shares to be sold by such Selling Stockholder hereunder; and

(v) Good and valid title to such Shares, free and clear of all liens, encumbrances, equities or claims, has been transferred to each of the several Underwriters.

In rendering the opinion in paragraph (iv), such counsel may rely upon a certificate of such Selling Stockholder in respect of matters of fact as to ownership of, and liens, encumbrances, equities or claims on, the Shares sold by such Selling Stockholder, provided that such counsel shall state that they believe that both you and they are justified in relying upon such certificate;

(e) [(i)] On the date of the Prospectus at a time prior to the execution of this Agreement, at 9:30 a.m., New York City time, on the effective date of any post-effective amendment to the Registration Statement filed subsequent to the date of this Agreement and also at each Time of Delivery, Arthur Andersen LLP shall have furnished to you a letter or letters, dated the respective dates of delivery thereof, in form and substance satisfactory to you, to the effect set forth in Annex I hereto (the executed copy of the letter delivered prior to the execution of this Agreement is attached as Annex I(a) hereto and a draft of the form of letter to be delivered on the effective date of any post-effective amendment to the Registration Statement and as of each Time of Delivery is attached as Annex I(b) hereto);

[(ii) On the date of the Prospectus at a time prior to the execution of this Agreement, at 9:30 a.m., New York City time, on the effective date of any post-effective amendment to the Registration Statement filed subsequent to the date of this Agreement and also at each Time of Delivery, KPMG LLP shall have furnished to you a letter or letters, dated the respective dates of delivery thereof, in form and substance satisfactory to you, to the effect set forth in Annex II hereto (the executed copy of the letter delivered prior to the execution of this Agreement is attached as Annex II(a) hereto and a draft of the form of letter to be delivered on the effective date of any post-effective amendment to the Registration Statement and as of each Time of Delivery is attached as Annex II(b) hereto);]

(f) (i) Neither the Company nor any of its subsidiaries shall have sustained since the date of the latest audited financial statements included or incorporated by reference in the Prospectus any loss or interference with its business from fire, explosion, flood or other calamity, whether or not covered by insurance, or from any labor dispute or court or governmental action, order or decree, otherwise than as set forth or contemplated in the Prospectus, and (ii) since the respective dates as of which information is given in the

Prospectus there shall not have been any change in the capital stock, capital lease obligations or long-term debt of the Company or any of its subsidiaries or any change, or any development involving a prospective change, in or affecting the general affairs, management, financial position, stockholders' equity or results of operations of the Company and its subsidiaries, taken as a whole, otherwise than as set forth or contemplated in the Prospectus, the effect of which, in any such case described in clause (i) or (ii), is in the judgment of Goldman, Sachs & Co., as representatives of the Underwriters, so material (to the Company and its subsidiaries taken as a whole) and adverse as to make it impracticable or inadvisable to proceed with the public offering or the delivery of the Shares being delivered at such Time of Delivery on the terms and in the manner contemplated in the Prospectus;

(g) On or after the date hereof (i) no downgrading shall have occurred in the rating accorded the Company's debt securities by any "nationally recognized statistical rating organization", as that term is defined by the Commission for purposes of Rule 436(g)(2) under the Act, and (ii) no such organization shall have publicly announced that it has under surveillance or review, with possible negative implications, its rating of any of the Company's debt securities;

(h) On or after the date hereof there shall not have occurred any of the following: (i) a suspension or material limitation in trading in securities generally on the New York Stock Exchange or on NASDAQ; (ii) a suspension or material limitation in trading in the Company's securities on NASDAQ; (iii) a general moratorium on commercial banking activities declared by either Federal or New York State authorities; or (iv) the outbreak or escalation of hostilities involving the United States or the declaration by the United States of a national emergency or war, if the effect of any such event specified in this clause (iv) in the judgment of Goldman, Sachs & Co. makes it impracticable or inadvisable to proceed with the public offering or the delivery of the Shares being delivered at such Time of Delivery on the terms and in the manner contemplated in the Prospectus;

(i) The Shares at such Time of Delivery shall have been duly listed for quotation on NASDAQ;

(j) The Company has obtained and delivered to the Underwriters executed copies of an agreement from each of the executive officers and directors of the Company and from each Selling Stockholder substantially to the effect set forth in Subsection 1(b)(iv) hereof in form and substance satisfactory to you;

(k) The Company shall have complied with the provisions of
Section 5(c) hereof with respect to the furnishing of prospectuses on the New York Business Day next succeeding the date of this Agreement; and

(l) The Company and the Selling Stockholders shall have furnished or caused to be furnished to you at such Time of Delivery certificates of officers of the Company and of the Selling Stockholders, respectively, satisfactory to you as to the accuracy of the representations and warranties of the Company and the Selling Stockholders, respectively, herein at and as of such Time of Delivery, as to the performance by the Company and the Selling Stockholders of all of their respective obligations hereunder to be performed at or prior to such Time of Delivery, and as to such other matters as you may reasonably request, and the Company shall have furnished or caused to be furnished certificates as to the matters set forth in subsections (a) and (f) of this Section.

8 (a) The Company and each of the Selling Stockholders, jointly and severally, will indemnify and hold harmless each Underwriter against any losses, claims, damages or liabilities, joint or several, to which such Underwriter may become subject, under the Act or otherwise, insofar as such losses, claims, damages or liabilities (or actions in respect thereof) arise out of or are based upon an untrue statement or alleged untrue statement of a material fact contained in any Preliminary Prospectus, the Registration Statement or the Prospectus, or any amendment or supplement thereto, or arise out of or are based upon the omission or alleged omission to state therein a material fact required to be stated therein or necessary to make the statements therein not misleading, and will reimburse each Underwriter for any legal or other expenses reasonably incurred by such Underwriter in connection with investigating or defending any such action or claim as such expenses are incurred; PROVIDED, HOWEVER, that the Company and the Selling Stockholders shall not be liable in any such case to the extent that any such loss, claim, damage or liability arises out of or is based upon an untrue statement or alleged untrue statement or omission or alleged omission made in any Preliminary Prospectus, the Registration Statement or the Prospectus or any such amendment or supplement in reliance upon and in conformity with written information furnished to the Company by any Underwriter through Goldman, Sachs & Co. expressly for use therein; and PROVIDED, FURTHER HOWEVER, that no Selling Stockholder (other than Mr. Schatz and Mr. Backman with respect to (ii) and (iii)) shall be liable in any such case to the extent that any such loss, claim, damage or liability arises out of or is based upon an untrue statement or alleged untrue statement or omission or alleged omission made in any Preliminary Prospectus, the Registration Statement or the Prospectus or any such amendment or supplement with respect to (i) the number of shares of Stock beneficially owned by any other Selling Stockholder; (ii) the percentage interests held by Douglas S. Schatz and G. Brent Backman in the leasing entities referred to in "Risk Factors-We lease our Fort Collins, Colorado facilities and a condominium from entities in which two individuals who are insiders and major stockholders have financial interests"; and (iii) the percentage interests which Mr. Schatz and Mr. Backman hold in AEI Properties.

(b) Each Underwriter will indemnify and hold harmless the Company and each Selling Stockholder against any losses, claims, damages or liabilities to which the Company or such Selling Stockholder may become subject, under the Act or otherwise, insofar as such losses, claims, damages or liabilities (or actions in respect thereof) arise out of or are based upon an untrue statement or alleged untrue statement of a material fact contained in any Preliminary Prospectus, the Registration Statement or the Prospectus, or any amendment or supplement thereto, or arise out of or are based upon the omission or alleged omission to state therein a material fact required to be stated therein or necessary to make the statements therein not misleading, in each case to the extent, but only to the extent, that such untrue statement or alleged untrue statement or omission or alleged omission was made in any Preliminary Prospectus, the Registration Statement or the Prospectus or any such amendment or supplement in reliance upon and in conformity with written information furnished to the Company by such Underwriter through Goldman, Sachs & Co. expressly for use therein; and will reimburse the Company and each Selling Stockholder for any legal or other expenses reasonably incurred by the Company or such Selling Stockholder in connection with investigating or defending any such action or claim as such expenses are incurred.

(c) Promptly after receipt by an indemnified party under subsection
(a) or (b) above of notice of the commencement of any action, such indemnified party shall, if a claim in respect thereof is to be made against the indemnifying party under such subsection, notify the indemnifying party in writing of the commencement thereof; but the omission so to notify the indemnifying party shall not relieve it from any liability which it may have to any indemnified party otherwise than under such subsection. In case any such action shall be brought against any indemnified party and it shall notify the indemnifying party of the commencement thereof, the indemnifying party shall be entitled to participate therein and, to the extent that it shall wish, jointly with any other indemnifying party similarly notified, to assume the defense thereof, with counsel satisfactory to such indemnified party (who shall not, except with the consent of the indemnified party, be counsel to the indemnifying party), and, after notice from the indemnifying party to such indemnified party of its election so to assume the defense thereof, the indemnifying party shall not be liable to such indemnified party under such subsection for any legal expenses of other counsel or any other expenses, in each case subsequently incurred by such indemnified party, in connection with the defense thereof other than reasonable costs of investigation. No indemnifying party shall, without the written consent of the indemnified party, effect the settlement or compromise of, or consent to the entry of any judgment with respect to, any pending or threatened action or claim in respect of which indemnification or contribution may be sought hereunder (whether or not the indemnified party is an actual or potential party to such action or claim) unless such settlement, compromise or judgment (i) includes an unconditional release of the indemnified party from all liability arising out of such action or claim and (ii) does not include a statement as to or an admission of fault, culpability or a failure to act, by or on behalf of any indemnified party.

(d) If the indemnification provided for in this Section 8 is unavailable to or insufficient to hold harmless an indemnified party under subsection (a) or (b) above in respect of any losses, claims, damages or liabilities (or actions in respect thereof) referred to therein, then each indemnifying party shall contribute to the amount paid or payable by such indemnified party as a result of such losses, claims, damages or liabilities (or actions in respect thereof) in such proportion as is appropriate to reflect the relative benefits received by the Company and the Selling Stockholders on the one hand and the Underwriters on the other from the offering of the Shares. If, however, the allocation provided by the immediately preceding sentence is not permitted by applicable law or if the indemnified party failed to give the notice required under subsection (c) above, then each indemnifying party shall contribute to such amount paid or payable by such indemnified party in such proportion as is appropriate to reflect not only such relative benefits but also the relative fault of the Company and the Selling Stockholders on the one hand and the Underwriters on the other in connection with the statements or omissions which resulted in such losses, claims, damages or liabilities (or actions in respect thereof), as well as any other relevant equitable considerations. The relative benefits received by the Company and the Selling Stockholders on the one hand and the Underwriters on the other shall be deemed to be in the same proportion as the total net proceeds from the offering (before deducting expenses) received by the Company and the Selling Stockholders bear to the total underwriting discounts and commissions received by the Underwriters, in each case as set forth in the table on the cover page of the Prospectus. The relative fault shall be determined by reference to, among other things, whether the

untrue or alleged untrue statement of a material fact or the omission or alleged omission to state a material fact relates to information supplied by the Company or the Selling Stockholders on the one hand or the Underwriters on the other and the parties' relative intent, knowledge, access to information and opportunity to correct or prevent such statement or omission. The Company, each of the Selling Stockholders and the Underwriters agree that it would not be just and equitable if contribution pursuant to this subsection (d) were determined by PRO RATA allocation (even if the Underwriters were treated as one entity for such purpose) or by any other method of allocation which does not take account of the equitable considerations referred to above in this subsection (d). The amount paid or payable by an indemnified party as a result of the losses, claims, damages or liabilities (or actions in respect thereof) referred to above in this subsection (d) shall be deemed to include any legal or other expenses reasonably incurred by such indemnified party in connection with investigating or defending any such action or claim. Notwithstanding the provisions of this subsection (d), no Underwriter shall be required to contribute any amount in excess of the amount by which the total price at which the Shares underwritten by it and distributed to the public were offered to the public exceeds the amount of any damages which such Underwriter has otherwise been required to pay by reason of such untrue or alleged untrue statement or omission or alleged omission. No person guilty of fraudulent misrepresentation (within the meaning of Section 11(f) of the Act) shall be entitled to contribution from any person who was not guilty of such fraudulent misrepresentation. The Underwriters' obligations in this subsection (d) to contribute are several in proportion to their respective underwriting obligations and not joint.

(e) The obligations of the Company and the Selling Stockholders under this Section 8 shall be in addition to any liability which the Company and the respective Selling Stockholders may otherwise have and shall extend, upon the same terms and conditions, to each person, if any, who controls any Underwriter within the meaning of the Act; and the obligations of the Underwriters under this Section 8 shall be in addition to any liability which the respective Underwriters may otherwise have and shall extend, upon the same terms and conditions, to each officer and director of the Company and to each person, if any, who controls the Company or any Selling Stockholder within the meaning of the Act.

9 (a) If any Underwriter shall default in its obligation to purchase the Shares which it has agreed to purchase hereunder at a Time of Delivery, you may in your discretion arrange for you or another party or other parties to purchase such Shares on the terms contained herein. If within thirty-six hours after such default by any Underwriter you do not arrange for the purchase of such Shares, then the Company and the Selling Stockholders shall be entitled to a further period of thirty-six hours within which to procure another party or other parties satisfactory to you to purchase such Shares on such terms. In the event that, within the respective prescribed periods, you notify the Company and the Selling Stockholders that you have so arranged for the purchase of such Shares, or the Company and the Selling Stockholders notify you that they have so arranged for the purchase of such Shares, you or the Company or the Selling Stockholders shall have the right to postpone such Time of Delivery for a period of not more than seven days, in order to effect whatever changes may thereby be made necessary in the Registration Statement or the Prospectus, or in any other documents or arrangements, and the Company agrees to file promptly any amendments to the

Registration Statement or the Prospectus which in your opinion may thereby be made necessary. The term "Underwriter" as used in this Agreement shall include any person substituted under this Section with like effect as if such person had originally been a party to this Agreement with respect to such Shares.

(b) If, after giving effect to any arrangements for the purchase of the Shares of a defaulting Underwriter or Underwriters by you and the Company and the Selling Stockholders as provided in subsection (a) above, the aggregate number of such Shares which remains unpurchased does not exceed one-eleventh of the aggregate number of all the Shares to be purchased at such Time of Delivery, then the Company and the Selling Stockholders shall have the right to require each non-defaulting Underwriter to purchase the number of Shares which such Underwriter agreed to purchase hereunder at such Time of Delivery and, in addition, to require each non-defaulting Underwriter to purchase its pro rata share (based on the number of Shares which such Underwriter agreed to purchase hereunder) of the Shares of such defaulting Underwriter or Underwriters for which such arrangements have not been made; but nothing herein shall relieve a defaulting Underwriter from liability for its default.

(c) If, after giving effect to any arrangements for the purchase of the Shares of a defaulting Underwriter or Underwriters by you and the Company and the Selling Stockholders as provided in subsection (a) above, the aggregate number of such Shares which remains unpurchased exceeds one-eleventh of the aggregate number of all of the Shares to be purchased at such Time of Delivery, or if the Company and the Selling Stockholders shall not exercise the right described in subsection (b) above to require non-defaulting Underwriters to purchase Shares of a defaulting Underwriter or Underwriters, then this Agreement (or, with respect to the Second Time of Delivery, the obligations of the Underwriters to purchase and of the Selling Stockholders to sell the Optional Shares) shall thereupon terminate, without liability on the part of any non-defaulting Underwriter or the Company or the Selling Stockholders, except for the expenses to be borne by the Company and the Selling Stockholders and the Underwriters as provided in Section 6 hereof and the indemnity and contribution agreements in Section 8 hereof; but nothing herein shall relieve a defaulting Underwriter from liability for its default.

10 The respective indemnities, agreements, representations, warranties and other statements of the Company, the Selling Stockholders and the several Underwriters, as set forth in this Agreement or made by or on behalf of them, respectively, pursuant to this Agreement, shall remain in full force and effect, regardless of any investigation (or any statement as to the results thereof) made by or on behalf of any Underwriter or any controlling person of any Underwriter, or the Company, or any of the Selling Stockholders, or any officer or director or controlling person of the Company, or any controlling person of any Selling Stockholder, and shall survive delivery of and payment for the Shares.

11 If this Agreement shall be terminated pursuant to Section 9 hereof, neither the Company nor the Selling Stockholders shall then be under any liability to any Underwriter except as provided in Sections 6 and 8 hereof; but, if for any other reason any Shares are not delivered by

or on behalf of the Company or a Selling Stockholder as provided herein, the Company and each of the Selling Stockholders pro rata (based on the number of Shares to be sold by the Company and the Selling Stockholders hereunder) will reimburse the Underwriters through you for all out-of-pocket expenses approved in writing by you, including fees and disbursements of counsel, reasonably incurred by the Underwriters in making preparations for the purchase, sale and delivery of the Shares, but the Company and the Selling Stockholders shall then be under no further liability to any Underwriter in respect of the Shares except as provided in Sections 6 and 8 hereof.

12 In all dealings hereunder, you shall act on behalf of each of the Underwriters, and the parties hereto shall be entitled to act and rely upon any statement, request, notice or agreement on behalf of any Underwriter made or given by you; and in all dealings with any Selling Stockholder hereunder, you and the Company shall be entitled to act and rely upon any statement, request, notice or agreement on behalf of such Selling Stockholder made or given by any or all of the Attorneys-in-Fact for such Selling Stockholder.

All statements, requests, notices and agreements hereunder shall be in writing, and if to the Underwriters shall be delivered or sent by mail, telex or facsimile transmission to you as the representatives at 32 Old Slip, 21st Floor, New York, New York 10005, Attention: Registration Department; if to any Selling Stockholder shall be delivered or sent by mail, telex or facsimile transmission to counsel for such Selling Stockholder at its address set forth in Schedule II hereto; and if to the Company shall be delivered or sent by mail, telex or facsimile transmission to the address of the Company set forth in the Registration Statement, Attention: Secretary; provided, however, that any notice to an Underwriter pursuant to Section 8(c) hereof shall be delivered or sent by mail, telex or facsimile transmission to such Underwriter at its address set forth in its Underwriters' Questionnaire or telex constituting such Questionnaire, which address will be supplied to the Company or the Selling Stockholders by you upon request. Any such statements, requests, notices or agreements shall take effect upon receipt thereof.

13 This Agreement shall be binding upon, and inure solely to the benefit of, the Underwriters, the Company and the Selling Stockholders and, to the extent provided in Sections 8 and 10 hereof, the officers and directors of the Company and each person who controls the Company, any Selling Stockholder or any Underwriter, and their respective heirs, executors, administrators, successors and assigns, and no other person shall acquire or have any right under or by virtue of this Agreement. No purchaser of any of the Shares from any Underwriter shall be deemed a successor or assign by reason merely of such purchase.

14 Time shall be of the essence of this Agreement. As used herein, the term "business day" shall mean any day when the Commission's office in Washington, D.C. is open for business.

15 THIS AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK WITHOUT GIVING EFFECT TO ANY CHOICE OF LAW PROVISIONS THEREOF.

16 This Agreement may be executed by any one or more of the parties hereto in any number of counterparts, each of which shall be deemed to be an original, but all such counterparts shall together constitute one and the same instrument.

If the foregoing is in accordance with your understanding, please sign and return to us four counterparts hereof, and upon the acceptance hereof by you, on behalf of each of the Underwriters, this letter and such acceptance hereof shall constitute a binding agreement among each of the Underwriters, the Company and each of the Selling Stockholders. It is understood that your acceptance of this letter on behalf of each of the Underwriters is pursuant to the authority set forth in a form of Agreement among Underwriters, the form of which shall be submitted to the Company and the Selling Stockholders for examination, upon request, but without warranty on your part as to the authority of the signers thereof.

Any person executing and delivering this Agreement as Attorney-in-Fact for a Selling Stockholder represents by so doing that he has been duly appointed as Attorney-in-Fact by such Selling Stockholder pursuant to a validly existing and binding Power-of-Attorney which authorizes such Attorney-in-Fact to take such action.

Very truly yours,

ADVANCED ENERGY INDUSTRIES, INC.

Title:

DOUGLAS S. SCHATZ
G. BRENT BACKMAN
RICHARD P. BECK
HOLLIS CASWELL
RICHARD SCHOLL
JOSEPH STACH

Title:
As Attorney-in-Fact acting on behalf of
each of the Selling Stockholders named in
Schedule II to in Schedule II to this
Agreement.

Accepted as of the date hereof

GOLDMAN, SACHS & CO.

                                                                    NUMBER OF OPTIONAL
                                             TOTAL NUMBER OF           SHARES TO BE
                   UNDERWRITER                 FIRM SHARES             PURCHASED IF
                   -----------               TO BE PURCHASED          MAXIMUM OPTION
                                         -----------------------         EXERCISED
                                                                  -----------------------
Goldman, Sachs & Co.

BancBoston Robertson Stephens

CIBC World Markets

                                         -----------------------  -----------------------
                                                2,000,000                 450,000
                Total                    -----------------------  -----------------------
                                         -----------------------  -----------------------

                                                                                    NUMBER OF OPTIONAL
                                                             TOTAL NUMBER OF           SHARES TO BE
                                  UNDERWRITER                  FIRM SHARES                SOLD IF
                                  -----------                   TO BE SOLD             MAXIMUM OPTION
                                                         -----------------------          EXERCISED
                                                                                  -----------------------
The Company.........................................                   1,000,000

         The Selling Stockholder(s):

                 Douglas S. Schatz (a)                                   875,000

                 G. Brent Backman (a)                                    875,000

                 Richard P. Beck (a)                                      50,000

                 Hollis Caswell (a)                                       50,000

                 Richard Scholl (a)                                      100,000

                 Joseph Stach (a)                                         50,000
                                                                       ---------                  -------
                                                                       2,000,000                  450,000





        Total.......................................
                                                                    ------------               ----------
                                                                    ------------               ----------