| UNITED      STATES                      |
|-----------------------------------------|
| SECURITIES      AND EXCHANGE COMMISSION |
| Washington,      D.C.  20549  |
| FORM      10-K/AAmendment      No.1     |

| (MARK      ONE)                                            |
|------------------------------------------------------------|
| (x)                                                        | Annual      Report Pursuant to Section 13 or 15(d) of the Securities Exchange Act of      1934 (Fee Required)For      the fiscal year ended March 31, 2007 |
| or                                                         |
| (  )                                             | Transition      Report Pursuant to Section 13 or 15(d) of the Securities and Exchange Act      of 1934For      the transition period from _______ to ________ |
|  Commission      File No. 0-12718                     |
|                                                       |
| SUPERTEX,      INC.                                        |
| (Exact      name of Registrant as specified in itscharter) |

| California                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     | 94-2328535                                                                       |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------|
| (State      or other jurisdiction of incorporation or organization)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            | (I.R.S.      Employer Identification No.)                                        |
|                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| 1235      Bordeaux Drive, Sunnyvale, California 94089                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
| (Address      of principal executive offices)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  |
| Registrant's      Telephone Number, Including Area Code:  (408)      222-8888                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |                                                                             |
| Securities      registered pursuant to Section 12(b) of the Act:                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               |
| Title      of each class: Common Stock                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         | Name      of each exchange on which registered: Nasdaq Global Select      Market |
| Securities      registered pursuant to Section 12(g) of the Act: None                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
|                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| Indicate      by check mark if the registrant is a well-known seasoned issuer, as      defined in Rule 405 of the Securities Act.  Yes  o   No  x                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
|                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| Indicate      by check mark if the registrant is not required to file reports pursuant      to Section 13 of Section 15(d) of the      Act.   Yes  o   No  x                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |
|                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| Indicate      by check mark whether the Registrant (1) has filed all reports required to      be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934      during the preceding 12 months (or for such shorter period that the      Registrant was required to file such reports), and (2) has been subject to      such filing requirements for the past 90 days. Yes  x   No  o                                                                                                                                                                                                                                                                                                                                                                                                                             |
|                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| Indicate      by check mark if disclosure of delinquent filers pursuant to Item 405 of      Regulation S-K (Sec. 229.405 of this chapter) is not contained herein, and      will not be contained, to the best of registrant’s knowledge, in      definitive proxy or information statements incorporated by reference in      Part III of this Form 10-K or any amendment to this Form 10-K. o                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
|                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| Indicate      by check mark whether the registrant is an accelerated filer (as defined      in Rule 12b-2 of the Act). Check one.    Large      accelerated filer o           Accelerated      filer x            Non-accelerated      filer o            Smaller      Reporting Company o                                                                                                                                                                                                                                                                                                                                                                                  |
|                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| As      of September 29, 2006, the last business day of the registrant’s most      recently completed second fiscal quarter, there were 13,679,179 shares of      the registrant’s common stock outstanding, and the aggregate market value      of such shares held by non-affiliates of the registrant was $435,238,896      based on the closing price reported on the NASDAQ National Market on      September 29, 2006. Shares of common stock held by officers, directors and      other persons who may be deemed “affiliates” of the Registrant have been      excluded from this computation.  This determination of affiliate      status is not necessarily a conclusive determination for other purposes.      The total number of shares outstanding of the Registrant's common stock as      of June 11, 2007, was 13,732,728. |
|                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| Documents Incorporated by      Reference:  Part III incorporates by reference portions      of the Company's definitive proxy statement for the Annual Meeting of      Shareholders held on August 17, 2007 (the "Proxy    Statement").                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                              |
|                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |

----

----

| Item      15.   Exhibits and Financial Statement      Schedules |                                                         |
|--------------------------------------------------------------------------------|--------------------------------------------------------------|
|                                                                           |                                                         |   |   |
| (a)                                                                            | The      following documents are filed as part of this form: |   |
|                                                                           |                                                         |   |   |

| 3.     | Exhibits.                       |
|--------|---------------------------------|
|   |                            |   |
|   | Exhibit                         | Exhibit      Description |
|   |                            |   |
|   | 2.1      (1)                    | Agreement      for purchases and sale of assets by and between Supertex, Inc. and Orbit      Semiconductor dated January 16, 1999. |
|   |                            |   |
|   | 3.1      (2)                    | Restated      Articles of Incorporation of Registrant filed May 21,  1980. |
|   |                            |   |
|   | 3.2      (2)                    | Certificate      of Amendment of Articles of Incorporation filed April 16,      1981. |
|   |                            |   |
|   | 3.3      (2)                    | Certificate      of Amendment of Articles of Incorporation filed September 30,      1983. |
|   |                            |   |
|   | 3.4      (3)                    | Certificate      of Amendment of Articles of Incorporation filed October 14,      1988. |
|   |                            |   |
|   | 3.5      (5)                    | Bylaws      of Registrant, as amended. |
|   |                            |   |
|   | 10      (2)                     | Deferred      Compensation Plan (Supplemental Employee Retirement Plan), which became      effective January 1, 1996. |
|   |                            |   |
|   | 10.2      (1)                   | Lease      Assignment agreement for 71 Vista Montana, San Jose, California, dated      February 1, 1999 among Orbit Semiconductor, as assignor, Sobrato      Development Companies #871, as landlord, and Supertex, Inc., as      assignee. |
|   |                            |   |
|   | 10.6      (4)    | 1991      Stock Option Plan which became effective, with form of stock option      agreement. |
|   |                            |   |
|   | 10.6a      (5)                  | 1991      Stock Option Plan, as amended as of August 4, 1995, with form of stock      option agreement. |
|   |                            |   |
|   | 10.6b      (6)                  | 1991      Stock Option Plan, as amended as of August 6, 1999, with form of stock      option agreement. |
|   |                            |   |
|   | 10.6c      (7)        | 2000      Employee Stock Purchase Plan. |
|   |                            |   |
|   | 10.6d      (8)                  | 2001      Stock Option Plan, which became effective, with form of stock option      agreement. |
|   |                            |   |
|   | 10.7      (2)                   | Profit      Sharing Plan. |
|   |                            |   |

----

|   | 21.1*                                                                                     | Subsidiary      of the Registrant.                                                                                                                                                                                                                                            |
|--------|-------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | 23.1*               | Consent      of PricewaterhouseCoopers LLP, Independent Registered Public Accounting      Firm.                                                                                                                                                                               |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | 24.1*                                                                                     | Power      of Attorney.                                                                                                                                                                                                                                                       |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | 31.1*                                                                                     | Certification      of Chief Executive Officer pursuant to Securities Exchange Act Rules      13a-14(a) and 15d-14(a), as adopted pursuant to Section 302 of the      Sarbanes-Oxley Act of 2002.                                                                              |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | 31.2*                                                                                     | Certification      of Chief Financial Officer pursuant to Securities Exchange Act Rules      13a-14(a) and 15d-14(a), as adopted pursuant to Section 302 of the      Sarbanes-Oxley Act of 2002.                                                                              |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | 31.3                                                                                      | Certification      of Chief Executive Officer pursuant to Securities Exchange Act Rules      13a-14(a) and 15d-14(a), as adopted pursuant to Section 302 of the      Sarbanes-Oxley Act of 2002.                                                                              |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | 31.4                                                                                      | Certification      of Chief Financial Officer pursuant to Securities Exchange Act Rules      13a-14(a) and 15d-14(a), as adopted pursuant to Section 302 of the      Sarbanes-Oxley Act of 2002.                                                                              |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | 32.1                                                                                      | Certification      of Chief Executive Officer pursuant to 18 U.S.C. Section 1350, as adopted      pursuant to Section 906 of the Sarbanes-Oxley Act of  2002.                                                                                                                 |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | 32.2                                                                                      | Certification      of Chief Financial Officer pursuant to 18 U.S.C. Section 1350, as adopted      pursuant to Section 906 of the Sarbanes-Oxley Act of  2002.                                                                                                                 |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | (1)                                                                                       | Incorporated      by reference to the exhibit of the same number filed with current report      on form 8-K dated January 19, 1999.                                                                                                                                           |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | (2)                                                                                       | Incorporated      by reference to exhibit of same number of Registrant's Registration      Statement on Form S-1 (File No. 2-86898), which became effective December      6, 1983.                                                                                            |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | (3)                                                                                       | Incorporated      by reference to exhibit filed with Quarterly Report on Form 10-Q for      period ended October 1, 1988.                                                                                                                                                     |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | (4)                                                                                       | Incorporated      by reference to exhibit filed with Annual Report on Form 10-K for year      ended March 31, 1991.                                                                                                                                                           |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | (5)                                                                                       | Incorporated      by reference to exhibit included in Registrant's Registration Statement on      Form S-8 (File No. 33-43691) which became effective September 1,      1995.                                                                                                 |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | (6)                                                                                       | Incorporated      by reference to exhibit included in Registrant's Registration Statement on      Form S-8 (File No. 33-43691) which became effective September 29,      1999.                                                                                                |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | (7)                                                                                       | Incorporated      by reference to exhibit included in Registrant's Registration      Statement on Form S-8 (File No. 333-47606) which became effective October      6, 2000.                                                                                             |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | (8)                                                                                       | Incorporated      by reference to Appendix B of the Registrants amended Proxy Statement      filed on August 7, 2001 (File No. 000-12718).  Corresponding      Registration Statement on Form S-8 (File No. 333-69594) became effective      on September 18, 2001. |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
| (b     | Exhibits  31.3,      31.4, 32.1 and 32.2 are filedherewith.                     |

----

|                                   |   | Supertex,      Inc. |
|----------------------------------------|--------|---------------------|
|                                   |   |                |   |
|                                   |   |                |   |
| Dated:  October      7, 2008 |   |                | /s/PHILLIP A.      KAGEL |
|                                   |   |                | Phillip      A. Kagel |
|                                   |   |                | Vice      President of Finance and Chief Financial Officer |
|                                   |   |                | (Principal      Financial and Accounting Officer) |

| Signature                             |   | Title                                                      |   | Date                 |
|---------------------------------------|--------|------------------------------------------------------------|--------|----------------------|
|                                  |   |                                                       |   |                 |
| /s/ HENRY C.      PAO                 |   | President,      Chief Executive Officer                    |   | October      7, 2008 |
| (Henry      C. Pao)                   |   | (Principal      Executive Officer)                         |   |                 |
|                                  |   |                                                       |   |                 |
|                                  |   |                                                       |   |                 |
| /s/ PHILLIP A.      KAGEL             |   | Vice      President of Finance and Chief Financial Officer |   | October      7, 2008 |
| (Phillip      A. Kagel)               |   | (Principal      Financial and Accounting Officer)          |   |                 |
|                                  |   |                                                       |   |                 |
|                                  |   |                                                       |   |                 |
| /s/ BENEDICT C. K.      CHOY *        |   | Senior      Vice President, Technology Development         |   | October      7, 2008 |
| (Benedict      C. K. Choy)            |   |                                                       |   |                 |
|                                  |   |                                                       |   |                 |
|                                  |   |                                                       |   |                 |
| /s/ W. MARK      LOVELESS*            |   | Director                                                   |   | October      7, 2008 |
| (W.      Mark Loveless)               |   |                                                       |   |                 |
|                                  |   |                                                       |   |                 |
|                                  |   |                                                       |   |                 |
| /s/ ELLIOTT SCHLAM      *             |   | Director                                                   |   | October      7, 2008 |
| (Elliott      Schlam)                 |   |                                                       |   |                 |
|                                  |   |                                                       |   |                 |
|                                  |   |                                                       |   |                 |
| /s/ MILTON FENG      *                |   | Director                                                   |   | October      7, 2008 |
| (Milton      Feng)                    |   |                                                       |   |                 |
|                                  |   |                                                       |   |                 |
|                                  |   |                                                       |   |                 |
| *By:  /s/      HENRY C. PAO |   | Attorney-in-fact                                           |   | October      7, 2008 |
| (Henry      C. Pao)                   |   |                                                       |   |                 |

----

SUPERTEX, INC.

|   | Exhibit                         | Exhibit      Description                                                                                                                                                                                                                    |
|--------|---------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|   |                            |                                                                                                                                                                                                                                        |
|   | 2.1      (1)                    | Agreement      for purchases and sale of assets by and between Supertex, Inc. and Orbit      Semiconductor dated January 16, 1999.                                                                                                          |
|   |                            |                                                                                                                                                                                                                                        |
|   | 3.1      (2)                    | Restated      Articles of Incorporation of Registrant filed May 21,  1980.                                                                                                                                                                  |
|   |                            |                                                                                                                                                                                                                                        |
|   | 3.2      (2)                    | Certificate      of Amendment of Articles of Incorporation filed April 16,      1981.                                                                                                                                                       |
|   |                            |                                                                                                                                                                                                                                        |
|   | 3.3      (2)                    | Certificate      of Amendment of Articles of Incorporation filed September 30,      1983.                                                                                                                                                   |
|   |                            |                                                                                                                                                                                                                                        |
|   | 3.4      (3)                    | Certificate      of Amendment of Articles of Incorporation filed October 14,      1988.                                                                                                                                                     |
|   |                            |                                                                                                                                                                                                                                        |
|   | 3.5      (5)                    | Bylaws      of Registrant, as amended.                                                                                                                                                                                                      |
|   |                            |                                                                                                                                                                                                                                        |
|   | 10      (2)                     | Deferred      Compensation Plan (Supplemental Employee Retirement Plan), which became      effective January 1, 1996.                                                                                                                       |
|   |                            |                                                                                                                                                                                                                                        |
|   | 10.2      (1)                   | Lease      Assignment agreement for 71 Vista Montana, San Jose, California, dated      February 1, 1999 among Orbit Semiconductor, as assignor, Sobrato      Development Companies #871, as landlord, and Supertex, Inc., as      assignee. |
|   |                            |                                                                                                                                                                                                                                        |
|   | 10.6      (4)    | 1991      Stock Option Plan which became effective, with form of stock option      agreement.                                                                                                                                               |
|   |                            |                                                                                                                                                                                                                                        |
|   | 10.6a      (5)                  | 1991      Stock Option Plan, as amended as of August 4, 1995, with form of stock      option agreement.                                                                                                                                     |
|   |                            |                                                                                                                                                                                                                                        |
|   | 10.6b      (6)                  | 1991      Stock Option Plan, as amended as of August 6, 1999, with form of stock      option agreement.                                                                                                                                     |
|   |                            |                                                                                                                                                                                                                                        |
|   | 10.6c      (7)        | 2000      Employee Stock Purchase Plan.                                                                                                                                                                                                     |
|   |                            |                                                                                                                                                                                                                                        |
|   | 10.6d      (8)                  | 2001      Stock Option Plan, which became effective, with form of stock option      agreement.                                                                                                                                              |
|   |                            |                                                                                                                                                                                                                                        |
|   | 10.7      (2)                   | Profit      Sharing Plan.                                                                                                                                                                                                                   |
|   |                            |                                                                                                                                                                                                                                        |

----

|   | 21.1*                                                                                     | Subsidiary      of the Registrant.                                                                                                                                                                                                                                            |
|--------|-------------------------------------------------------------------------------------------|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | 23.1*               | Consent      of PricewaterhouseCoopers LLP, Independent Registered Public Accounting      Firm.                                                                                                                                                                               |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | 24.1*                                                                                     | Power      of Attorney.                                                                                                                                                                                                                                                       |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | 31.1*                                                                                     | Certification      of Chief Executive Officer pursuant to Securities Exchange Act Rules      13a-14(a) and 15d-14(a), as adopted pursuant to Section 302 of the      Sarbanes-Oxley Act of 2002.                                                                              |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | 31.2*                                                                                     | Certification      of Chief Financial Officer pursuant to Securities Exchange Act Rules      13a-14(a) and 15d-14(a), as adopted pursuant to Section 302 of the      Sarbanes-Oxley Act of 2002.                                                                              |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | 31.3                                                                                      | Certification      of Chief Executive Officer pursuant to Securities Exchange Act Rules      13a-14(a) and 15d-14(a), as adopted pursuant to Section 302 of the      Sarbanes-Oxley Act of 2002.                                                                              |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | 31.4                                                                                      | Certification      of Chief Financial Officer pursuant to Securities Exchange Act Rules      13a-14(a) and 15d-14(a), as adopted pursuant to Section 302 of the      Sarbanes-Oxley Act of 2002.                                                                              |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | 32.1                                                                                      | Certification      of Chief Executive Officer pursuant to 18 U.S.C. Section 1350, as adopted      pursuant to Section 906 of the Sarbanes-Oxley Act of  2002.                                                                                                                 |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | 32.2                                                                                      | Certification      of Chief Financial Officer pursuant to 18 U.S.C. Section 1350, as adopted      pursuant to Section 906 of the Sarbanes-Oxley Act of  2002.                                                                                                                 |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | (1)                                                                                       | Incorporated      by reference to the exhibit of the same number filed with current report      on form 8-K dated January 19, 1999.                                                                                                                                           |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | (2)                                                                                       | Incorporated      by reference to exhibit of same number of Registrant's Registration      Statement on Form S-1 (File No. 2-86898), which became effective December      6, 1983.                                                                                            |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | (3)                                                                                       | Incorporated      by reference to exhibit filed with Quarterly Report on Form 10-Q for      period ended October 1, 1988.                                                                                                                                                     |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | (4)                                                                                       | Incorporated      by reference to exhibit filed with Annual Report on Form 10-K for year      ended March 31, 1991.                                                                                                                                                           |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | (5)                                                                                       | Incorporated      by reference to exhibit included in Registrant's Registration Statement on      Form S-8 (File No. 33-43691) which became effective September 1,      1995.                                                                                                 |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | (6)                                                                                       | Incorporated      by reference to exhibit included in Registrant's Registration Statement on      Form S-8 (File No. 33-43691) which became effective September 29,      1999.                                                                                                |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | (7)                                                                                       | Incorporated      by reference to exhibit included in Registrant's Registration      Statement on Form S-8 (File No. 333-47606) which became effective October      6, 2000.                                                                                             |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | (8)                                                                                       | Incorporated      by reference to Appendix B of the Registrants amended Proxy Statement      filed on August 7, 2001 (File No. 000-12718).  Corresponding      Registration Statement on Form S-8 (File No. 333-69594) became effective      on September 18, 2001. |
|   |                                                                                      |                                                                                                                                                                                                                                                                          |
|   | *      Previously filed                                                                   |

----

| 1. | I      have reviewed this Amendment No. 1 (to Form 10-K) of Supertex, Inc., a      California corporation; |
|----|------------------------------------------------------------------------------------------------------------|

| 2. | Based      on my knowledge, this report does not contain any untrue statement of a      material fact or omit to state a material fact necessary to make the      statements made, in light of the circumstances under which such statements      were made, not misleading with respect to the period covered by this      report. |
|----|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

|   |   |
|--------|--------|

| Date:      October 7, 2008 | /s/  HENRY      C. PAO |
|----------------------------|----------------------------------|
|                       | Henry      C. Pao, Ph.D.         |
|                       | Chief      Executive Officer     |

| 1. | I      have reviewed this amendment No. 1 (to Form 10-K) of Supertex, Inc., a      California corporation; |
|----|------------------------------------------------------------------------------------------------------------|

| 2. | Based      on my knowledge, this report does not contain any untrue statement of a      material fact or omit to state a material fact necessary to make the      statements made, in light of the circumstances under which such statements      were made, not misleading with respect to the period covered by this      report. |
|----|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

|   |   |
|--------|--------|

| Date:      October 7, 2008 | /s/  PHILLIP      A. KAGEL                                 |
|----------------------------|----------------------------------------------------------------------|
|                       | Phillip      A. Kagel                                                |
|                       | Vice      President of Finance and Chief Financial Officer           |
|                       | (Principal      Financial Officer and Principal Accounting  Officer) |

----

|   | (i) | the      Annual Report of the Company on Form 10-K for the period ending March      31, 2007 (the “Report”), fully complies with the requirements of Section      13(a) or 15(d), whichever is applicable, of the Securities Exchange Act of      1934, and |
|--------|-----|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

|   | (ii) | the      information contained in the Report fairly presents, in all material      respects, the financial condition and results of operations of the      Company. |
|--------|------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| Date:      October 7, 2008 | /s/ HENRY C.      PAO        |
|----------------------------|------------------------------|
|                       | Henry      C. Pao, Ph.D.     |
|                       | Chief      Executive Officer |

| The      material contained in this Exhibit 32.1 is not deemed “filed” with the SEC      and is not to be incorporated by reference into any filing of the Company      under the Securities Act of 1933 or the Securities Exchange Act of 1934,      whether made before or after the date hereof and irrespective of any      general incorporation language contained in such  filing. |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

|   | (i) | the      Annual Report of the Company on Form 10-K for the period ending March      31, 2007 (the “Report”), fully complies with the requirements of Section      13(a) or 15(d), whichever is applicable, of the Securities Exchange Act of      1934, and |
|--------|-----|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

|   | (ii) | the      information contained in the Report fairly presents, in all material      respects, the financial condition and results of operations of the      Company. |
|--------|------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------|

| Date:      October 7, 2008 | /s/ PHILLIP A.      KAGEL                                            |
|----------------------------|----------------------------------------------------------------------|
|                       | Phillip      A. Kagel                                                |
|                       | Vice      President of Finance and Chief Financial Officer           |
|                       | (Principal      Financial Officer and Principal Accounting  Officer) |

| The      material contained in this Exhibit 32.2 is not deemed “filed” with the SEC      and is not to be incorporated by reference into any filing of the Company      under the Securities Act of 1933 or the Securities Exchange Act of 1934,      whether made before or after the date hereof and irrespective of any      general incorporation language contained in such  filing. |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

----