AMENDMENT to the AGREEMENT FOR WAFER PRODUCTION AND TESTING Between Advanced Power Technology 405 S.W. Columbia Street, Bend,Oregon, USA and Infineon Technologies Austria AG Siemensstr. 2, 9500 Villach, Austria

Exhibit 10.37

AMENDMENT to the

AGREEMENT FOR WAFER PRODUCTION AND TESTING

Between

Advanced Power Technology

405 S.W. Columbia Street, Bend, Oregon, USA

and

Infineon Technologies Austria AG

Siemensstr. 2, 9500 Villach, Austria

This Amendment is effective as of the 1st day of July, 2005 and remains in effect through June 30th, 2006.

WHEREAS, Advanced Power Technology (hereinafter “APT”) and Siemens Aktiengesellschaft (hereinafter “Siemens”) entered into the Agreement for Wafer Production and Testing on February 11,1998 (hereinafter “Basic Agreement”);

WHEREAS, the Basic Agreement was amended in the Amendment to the Agreement for Wafer Production and Testing (hereinafter “Amendment”) between APT and Infineon Technologies AG, Munich, Germany, the latter being the legal successor of Siemens, on July 19, 2000 (both Agreements to be referred hereafter as “Agreements”); The primary purpose of the amendment being to

•                 agree to a more formal set of communications for all matters relative to these agreements.

•                 fix capacity by month committed to APT in terms of Wafer Starts Per Week (wspw) thru September 2001.

•                 fix wafer/die pricing through September 2001 on a [ * ] wspw basis and establish annual negotiations thereafter.

•                 express Infineon’s consent to have the amendment filed with the US SEC.

WHEREAS, both Agreements were amended February 5, 2001 by an Extension Agreement (also to be referred to hereafter as “Agreements”); The primary purpose of this amendment being to

•                 extend the scope of the Agreement to include APT’s MOSVI and MOSVII technologies and deliver wafers to APT based on these processes accordingly;

WHEREAS, both Agreements were amended January 1, 2002

•                 revised wafer/die pricing for wafer/die shipments to APT during Calendar Year (CY) 2002. (January 1, 2002 thru December 31, 2002)

[ * ] = CONFIDENTIAL TREATMENT REQUESTED

•                 a minimum wspw volume guarantee by APT.

•                 an additional price reduction opportunity for APT in the form of a rebate if the total number of wafers started in CY2002 meets or exceeds a predetermined quantity.

WHEREAS, the previous agreements were amended on January 6, 2003 to

•                 extend the scope of the Agreements to include APT’s MosVII IGET technology and deliver wafers processed to a mutually agreed upon process flow to APT based on these processes accordingly

•                 agree that during the transfer period of the MosVII IGBT process a cost of [ * ] will be shared [ * ] between APT and Infineon, billed to APT on a monthly basis.

WHEREAS, the previous agreements and amendments are assigned from Infineon Technologies AG, Munich, Germany, to lnfineon Technologies Austria AG (hereinafter “lnfineon Austria”)

WHEREAS, the previous agreements were amended effective April 1, 2004 to

•                 agree on MosV die prices and Mos6&7 wafer prices.

•                 Re-establish APT start and Infineon capacity commitments

NOW, THEREAFTER, based on mutual promises contained herein and intending to be legally bound, the parties agree to the following terms and conditions:

1.              Die prices for MosV technology effective July 6, 2005 are reflected in Exhibit A.

2.              Die prices are established for Mos VII & Mos VII IGBT effective July 6, 2005 as reflected in Exhibit A

3.              Requirement for [ * ] wafer starts per week for MOSVI/VII as agreed in the amendment effective May 2001, section 3.1 is hereby waived. Total start requirements for APT is defined in Section 4 below.

4.              The Minimum Volume Commitment of APT stays at [ * ] wspw and start rules guided by the first week starts being fixed, the next 7 weeks allowed delta being [ * ], the following 5 weeks allowed delta being [ * ], and no limits to the % delta after that, apply.

5.              Infineon Austria will use commercially reasonable efforts to support APT’s requirements in the event that a weekly capacity of more than [ * ] wspw is required within the rules of forecast changes defined in paragraph 4 above.

6.              Key Account Manager charges are terminated.

7.              In case no agreement can be achieved during the next annual negotiation by the end of

[ * ] = CONFIDENTIAL TREATMENT REQUESTED

June 2006 the prices and volumes based on the latest confirmed monthly forecast will continue to apply. Prices then in existence are those in place at the time of that annual negotiation, the volumes confirmed in the latest monthly forecast define the maximum capacity commitment of Infineon to APT for the consecutive 6 months beginning July 1, 2006 and will be [ * ] wspw for following 6 months. During this period APT agrees to start a minimum of [ * ] WSPW including wafers started on a “risk basis” as defined in prior agreements.

MISCELLANEOUS

7.              Infineon Austria hereby expressly gives its consent to have this agreement filed with the US SEC with the understanding that confidential information such as that related to pricing, volume, and other special arrangements be omitted.

S.             Except as otherwise explicitly amended in paragraphs 1 to 6 above, the terms and conditions of the Basic Agreement and its prior Amendments shall remain in full force and effect.

[ * ] = CONFIDENTIAL TREATMENT REQUESTED

EXHIBIT A

DIE BASED PRICING

[ * ] = CONFIDENTIAL TREATMENT REQUESTED

WAFER BASED PRICING

DIE BASED PRICING

[ * ] = CONFIDENTIAL TREATMENT REQUESTED

[ * ] = CONFIDENTIAL TREATMENT REQUESTED

DIE BASED PRICING

[ * ] = CONFIDENTIAL TREATMENT REQUESTED

[ * ] = CONFIDENTIAL TREATMENT REQUESTED