Sec Form 4 Filing - BLEGEN THEODORE @ MONOLITHIC POWER SYSTEMS INC - 2021-02-02

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person BLEGEN THEODORE 2. Issuer Name and Ticker or Trading Symbol MONOLITHIC POWER SYSTEMS INC [ MPWR] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner X __ Officer (give title below) _____ Other (specify below) CFO (Last) (First) (Middle) 5808 LAKE WASHINGTON BLVD NE 3. Date of Earliest Transaction (MM/DD/YY) 02/02/2021 (Street) KIRKLAND, WA98033 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) __ X __ Form filed by One Reporting Person _____ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 02/02/2021( 1 ) M( 1 ) 20,105 ( 1 ) A $ 0 135,845 D Common Stock 02/02/2021 A 41,196 ( 2 ) A $ 30 177,041 D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Performance Shares ( 1 ) 02/02/2021 M( 1 ) 20,105 ( 1 ) ( 1 ) Common Stock 20,105 $ 0 0 D

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other BLEGEN THEODORE 5808 LAKE WASHINGTON BLVD NE KIRKLAND, WA98033 CFO Signatures By: Saria Tseng For: Bernie Blegen 02/04/2021 Signature of Reporting Person Date

Explanation of Responses:

( 1 )On July 21, 2020, the reporting person was granted a target number of 4,021 performance units and can earn up to a maximum of 20,105 performance units subject to price targets ranging from $260 to $300 over a performance period from July 21, 2020 to July 20, 2023. In addition, all performance units are subject to the achievement of a business operating goal with a performance period through December 31, 2021. 75% of the performance units are subject to time-based vesting and require service through July 20, 2023, and the remaining 25% of the performance units are subject to time-based vesting and require service through July 20, 2024. Once vested, the performance units have a post-vesting sales restriction period of one year. On February 2, 2021, the Compensation Committee determined that the five price targets and the operating goal had been satisfied, which resulted in 20,105 units being credited, subject to time based vesting above. ( 2 )On February 11, 2019, the reporting person was granted a target of 13,732 shares of restricted stock units, with the right to earn up to 300% of the target shares, subject to satisfaction of pre-determined, performance-based vesting criteria. On February 2, 2021, the Company's Compensation Committee of the Board of Directors determined and approved the achievement of the performance criteria for the restricted stock units, which resulted in 27,464 additional shares being earned by the reporting person. Of the restricted stock units that were awarded, 20,598 will vest immediately and 20,598 will vest quarterly in the next two years.

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.

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