Exhibit 10.4 FIRST AMENDMENT TO CREDIT AGREEMENT

THIS AMENDMENT TO CREDIT AGREEMENT (this "Amendment") is entered into as of August 2, 2011, by and between POWER INTEGRATIONS, INC., a Delaware corporation ("Borrower"), and WELLS FARGO BANK, NATIONAL ASSOCIATION ("Bank").

WHEREAS, Borrower is currently indebted to Bank pursuant to the terms and conditions of that certain Credit Agreement between Borrower and Bank dated as of February 22, 2011, as amended from time to time ("Credit Agreement").

WHEREAS, Bank and Borrower have agreed to certain changes in the terms and conditions set forth in the Credit Agreement and have agreed to amend the Credit Agreement to reflect said changes.

NOW, THEREFORE, for valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the parties hereto agree that the Credit Agreement shall be amended as follows:

“(b)     Letter of Credit Subfeature. As a subfeature under the Line of Credit, Bank agrees from time to time during the term thereof to issue or cause an affiliate to issue commercial and standby letters of credit for the account of Borrower to back performance (each, a "Letter of Credit" and collectively, "Letters of Credit"); provided however, that the aggregate undrawn amount of all outstanding Letters of Credit shall not at any time exceed Twenty Million Dollars ($20,000,000.00). Unless cash secured to Bank's satisfaction, no Letter of Credit shall have an expiration date subsequent to the maturity date of the Line of Credit. The undrawn amount of all Letters of Credit shall be reserved under the Line of Credit and shall not be available for borrowings thereunder. Each Letter of Credit shall be subject to the additional terms and conditions of the Letter of Credit agreements, applications and any related documents required by Bank in connection with the issuance thereof. Each drawing paid under a Letter of Credit shall be deemed an advance under the Line of Credit and shall be repaid by Borrower in accordance with the terms and conditions of this Agreement applicable to such advances; provided however, that if advances under the Line of Credit are not available, for any reason, at the time any drawing is paid, then Borrower shall immediately pay to Bank the full amount drawn, together with interest thereon from the date such drawing is paid to the date such amount is fully repaid by Borrower, at the rate of interest applicable to advances under the Line of Credit. In such event Borrower agrees that Bank, in its sole discretion, may debit any account maintained by Borrower with Bank for the amount of any such drawing.”

2. Section 1.2 (c) is hereby deleted in its entirety, and the following substituted therefor:

“(c) Standby and Commercial Letter of Credit Fees. Borrower shall pay to Bank (i) fees upon the issuance of each Standby and Commercial Letter of Credit equal to one and one quarter percent (1.25%) per annum (computed on the basis of a 360-day year, actual days elapsed) of the face amount thereof, and (ii) fees upon the payment or negotiation of each

drawing under any Standby and Commercial Letter of Credit and fees upon the occurrence of any other activity with respect to any Standby and Commercial Letter of Credit (including without limitation, the transfer, amendment or cancellation of any Standby and Commercial Letter of Credit) determined in accordance with Bank's standard fees and charges then in effect for such activity.”

3. Except as specifically provided herein, all terms and conditions of the Credit Agreement remain

in full force and effect, without waiver or modification. All terms defined in the Credit Agreement shall have the same meaning when used in this Amendment. This Amendment and the Credit Agreement shall be read together, as one document.

4. Borrower hereby remakes all representations and warranties contained in the Credit Agreement and reaffirms all covenants set forth therein. Borrower further certifies that as of the date of this Amendment there exists no Event of Default as defined in the Credit Agreement, nor any condition, act or event which with the giving of notice or the passage of time or both would constitute any such Event of Default.

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed as of the day and year first written above.