Monolithic Power CEO files Form 4 after open‑market sales

Rhea-AI Filing Summary

Monolithic Power Systems (MPWR) reported insider transactions by CEO and director Michael R. Hsing. On 11/12/2025, he executed multiple open‑market sales of common stock at disclosed weighted‑average prices, with per‑line price ranges provided.

Following the transactions, Hsing beneficially owns 918,669 shares directly. He also holds indirect positions of 133,040 shares via the M Hsing 04 Trust and 12,825 shares via the ZH Family 2020 Trust.

Insights

Insider trading and disclosure analyst

CEO reported open‑market sales; substantial holdings remain.

The filing lists multiple Form 4 code “S” sales by Michael R. Hsing on 11/12/2025. Prices are reported as weighted averages for each tranche, with detailed intra‑range prices available upon request as noted in the footnotes.

After these trades, direct beneficial ownership is 918,669 shares, with additional indirect holdings of 133,040 and 12,825 shares via named trusts. No derivative securities are reported in Table II. The filing documents transactions and remaining ownership; actual market impact depends on broader trading and holder decisions.

Insider Trade Summary

Net Seller: 37,000 shares ($35,724,380)

Net Sell 21 txns

Insider Hsing Michael

Role CEO

Sold 37,000 shs ($35.72M)

Type	Security	Shares	Price	Value
Sale	Common Stock	403	$957.58	$386K
Sale	Common Stock	2,799	$958.34	$2.68M
Sale	Common Stock	440	$959.36	$422K
Sale	Common Stock	403	$960.45	$387K
Sale	Common Stock	1,904	$961.63	$1.83M
Sale	Common Stock	2,817	$962.61	$2.71M
Sale	Common Stock	3,552	$963.47	$3.42M
Sale	Common Stock	3,264	$964.47	$3.15M
Sale	Common Stock	5,619	$965.50	$5.43M
Sale	Common Stock	6,562	$966.45	$6.34M
Sale	Common Stock	3,024	$967.41	$2.93M
Sale	Common Stock	2,072	$968.37	$2.01M
Sale	Common Stock	975	$969.62	$945K
Sale	Common Stock	728	$970.29	$706K
Sale	Common Stock	59	$971.81	$57K
Sale	Common Stock	461	$972.78	$448K
Sale	Common Stock	298	$973.73	$290K
Sale	Common Stock	633	$979.59	$620K
Sale	Common Stock	987	$980.06	$967K
holding	Common Stock	--	--	--
holding	Common Stock	--	--	--

Holdings After Transaction: Common Stock — 955,266 shares (Direct); Common Stock — 133,040 shares (Indirect, by M Hsing 04 Trust)

Footnotes (1)

1. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $957.18 to $957.95. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $958.06 to $958.88. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $959.01 to $959.56. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $960.00 to $960.74. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $961.07 to $961.98. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $962.02 to $962.99. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $963.00 to $963.99. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $964.00 to $964.92. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $965.00 to $965.98. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $966.00 to $ 966.99. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $967.00 to $967.93. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $968.01 to $968.94. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $969.14 to $969.98. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $970.02 to $970.85. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $971.74 to $971.96. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $972.05 to $972.98. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $973.45 to $973.84. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $979.59 to $979.60. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $980.00 to $980.25. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.

Form 4 Insider Transactions: What Each Field Means →

SEC Form 4

FORM 4

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
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

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

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Hsing Michael

(Last) (First) (Middle)

1555 PALM BEACH LAKES BLVD.

(Street)

WEST PALM BEACH FL 33401

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
MONOLITHIC POWER SYSTEMS INC [ MPWR ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	CEO

3. Date of Earliest Transaction (Month/Day/Year)
11/12/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	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	11/12/2025		S		403	D	$957.58(1)	955,266	D
Common Stock	11/12/2025		S		2,799	D	$958.34(2)	952,467	D
Common Stock	11/12/2025		S		440	D	$959.36(3)	952,027	D
Common Stock	11/12/2025		S		403	D	$960.45(4)	951,624	D
Common Stock	11/12/2025		S		1,904	D	$961.63(5)	949,720	D
Common Stock	11/12/2025		S		2,817	D	$962.61(6)	946,903	D
Common Stock	11/12/2025		S		3,552	D	$963.47(7)	943,351	D
Common Stock	11/12/2025		S		3,264	D	$964.47(8)	940,087	D
Common Stock	11/12/2025		S		5,619	D	$965.5(9)	934,468	D
Common Stock	11/12/2025		S		6,562	D	$966.45(10)	927,906	D
Common Stock	11/12/2025		S		3,024	D	$967.41(11)	924,882	D
Common Stock	11/12/2025		S		2,072	D	$968.37(12)	922,810	D
Common Stock	11/12/2025		S		975	D	$969.62(13)	921,835	D
Common Stock	11/12/2025		S		728	D	$970.29(14)	921,107	D
Common Stock	11/12/2025		S		59	D	$971.81(15)	921,048	D
Common Stock	11/12/2025		S		461	D	$972.78(16)	920,587	D
Common Stock	11/12/2025		S		298	D	$973.73(17)	920,289	D
Common Stock	11/12/2025		S		633	D	$979.59(18)	919,656	D
Common Stock	11/12/2025		S		987	D	$980.06(19)	918,669	D
Common Stock								133,040	I	by M Hsing 04 Trust
Common Stock								12,825	I	ZH Family 2020 Trust

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 (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	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 (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (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: 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

Explanation of Responses:

1. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $957.18 to $957.95. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.

2. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $958.06 to $958.88. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.

3. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $959.01 to $959.56. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.

4. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $960.00 to $960.74. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.

5. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $961.07 to $961.98. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.

6. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $962.02 to $962.99. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.

7. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $963.00 to $963.99. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.

8. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $964.00 to $964.92. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.

9. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $965.00 to $965.98. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.

10. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $966.00 to $ 966.99. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.

11. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $967.00 to $967.93. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.

12. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $968.01 to $968.94. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.

13. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $969.14 to $969.98. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.

14. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $970.02 to $970.85. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.

15. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $971.74 to $971.96. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.

16. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $972.05 to $972.98. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.

17. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $973.45 to $973.84. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.

18. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $979.59 to $979.60. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.

19. The price is the weighted average sale price for the transactions reported on this line. The prices for the transactions reported on this line range from $980.00 to $980.25. The reporting person undertakes to provide, upon request by the staff of the Securities and Exchange Commission, the issuer, or a security holder of the issuer, full information regarding the number of shares sold at each separate price.

Remarks:

	/s/ Saria Tseng, attorney-in-fact for Mr. Michael R. Hsing	11/12/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What insider activity did MPWR disclose?

CEO Michael R. Hsing reported multiple open‑market sales of MPWR common stock on 11/12/2025 with code “S”.

What prices were involved in the MPWR insider sales?

Each line shows a weighted‑average price with ranges disclosed; across the footnotes, ranges span approximately $957.18 to $980.25.

How many MPWR shares does the CEO own after the sales?

Direct beneficial ownership is 918,669 shares. Indirect holdings are 133,040 shares (M Hsing 04 Trust) and 12,825 shares (ZH Family 2020 Trust).

Were any derivative securities reported?

No. Table II shows no derivative securities acquired, disposed of, or beneficially owned.

What transaction code appears on the MPWR Form 4?

The filing lists transaction code S, indicating open‑market or private sale of non‑derivative securities.