[Form 4] MONOLITHIC POWER SYSTEMS INC Insider Trading Activity

Monolithic Power Systems (MPWR) executive Bernie Blegen, EVP and CFO, reported open-market sales of common stock on 11/03/2025 pursuant to a Rule 10b5-1 trading plan adopted on 2/26/2025.

Rhea-AI Filing Summary

Monolithic Power Systems (MPWR) executive Bernie Blegen, EVP and CFO, reported open-market sales of common stock on 11/03/2025 pursuant to a Rule 10b5-1 trading plan adopted on 2/26/2025.

The sales were executed in multiple small lots at weighted average prices, including $1,013.62, $1,019.49, and $1,038.41 per share. Following these transactions, Blegen beneficially owns 74,332 shares directly.

He also reports indirect holdings of 5,331 shares in the Irrevocable Trust FBO Sarah N. Blegen and 5,331 shares in the Irrevocable Trust FBO Theodore F. Blegen.

Insider Trade Summary

Net Seller: 3,000 shares

Net Sell 24 txns

Insider BLEGEN THEODORE

Role EVP and CFO

Sold 3,000 shs ($3.07M)

Type	Security	Shares	Price	Value
Sale	Common Stock	204	$1,013.62	$207K
Sale	Common Stock	135	$1,014.47	$137K
Sale	Common Stock	80	$1,016.51	$81K
Sale	Common Stock	6	$1,017.78	$6K
Sale	Common Stock	180	$1,018.01	$183K
Sale	Common Stock	181	$1,019.49	$185K
Sale	Common Stock	160	$1,020.30	$163K
Sale	Common Stock	168	$1,021.28	$172K
Sale	Common Stock	40	$1,022.28	$41K
Sale	Common Stock	291	$1,023.32	$298K
Sale	Common Stock	208	$1,024.86	$213K
Sale	Common Stock	43	$1,025.91	$44K
Sale	Common Stock	200	$1,027.49	$205K
Sale	Common Stock	240	$1,028.43	$247K
Sale	Common Stock	246	$1,029.45	$253K
Sale	Common Stock	210	$1,030.00	$216K
Sale	Common Stock	17	$1,031.86	$18K
Sale	Common Stock	184	$1,032.07	$190K
Sale	Common Stock	80	$1,033.00	$83K
Sale	Common Stock	40	$1,034.99	$41K
Sale	Common Stock	40	$1,035.25	$41K
Sale	Common Stock	47	$1,038.41	$49K
holding	Common Stock	--	--	--
holding	Common Stock	--	--	--

Holdings After Transaction: Common Stock — 74,332 shares (Direct); Common Stock — 5,331 shares (Indirect, Irrevocable Trust FBO Sarah N. Blegen); Common Stock — 5,331 shares (Indirect, Irrevocable Trust FBO Theodore F. Blegen)

Footnotes (15)

1. F1. These transactions were made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on 2/26/2025.
2. F2. 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 $1,013.45 to $1,013.75. 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. F3. 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 $1,014.12 to $1,014.64. 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. F4. 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 $1,016.43 to $1,016.59. 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. F5. 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 $1,019.10 to $1,019.68. 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. F6. 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 $1,020.20 to $1,020.40. 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. F7. 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 $1,021.04 to $1,021.32. 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. F8. 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 $1,023.07 to $1,023.98. 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.
9. F9. 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 $1,024.02 to $1,024.99. 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.
10. F10. 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 $1,025.00 to $1,025.98. 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.
11. F11. 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 $1,027.03 to $1,027.89. 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. F12. 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 $1,028.00 to $1,028.85. 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.
13. F13. 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 $1,029.14 to $1,029.77. 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. F14. 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 $1,032.00 to $1,032.18. 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. F15. 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 $1,038.40 to $1,038.42. 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.

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Accepted by SEC EDGAR 11/04/2025 - 07:31 PM Learn about SEC filing dates

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).

X

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^*

BLEGEN THEODORE

(Last) (First) (Middle)

5808 LAKE WASHINGTON BLVD NE

(Street)

KIRKLAND WA 98033

(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)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	EVP and CFO

3. Date of Earliest Transaction (Month/Day/Year)
11/03/2025

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	11/03/2025		S		204(1)	D	$1,013.62(2)	77,128	D
Common Stock	11/03/2025		S		135(1)	D	$1,014.47(3)	76,993	D
Common Stock	11/03/2025		S		80(1)	D	$1,016.51(4)	76,913	D
Common Stock	11/03/2025		S		6(1)	D	$1,017.78	76,907	D
Common Stock	11/03/2025		S		180(1)	D	$1,018.01	76,727	D
Common Stock	11/03/2025		S		181(1)	D	$1,019.49(5)	76,546	D
Common Stock	11/03/2025		S		160(1)	D	$1,020.3(6)	76,386	D
Common Stock	11/03/2025		S		168(1)	D	$1,021.28(7)	76,218	D
Common Stock	11/03/2025		S		40(1)	D	$1,022.28	76,178	D
Common Stock	11/03/2025		S		291(1)	D	$1,023.32(8)	75,887	D
Common Stock	11/03/2025		S		208(1)	D	$1,024.86(9)	75,679	D
Common Stock	11/03/2025		S		43(1)	D	$1,025.91(10)	75,636	D
Common Stock	11/03/2025		S		200(1)	D	$1,027.49(11)	75,436	D
Common Stock	11/03/2025		S		240(1)	D	$1,028.43(12)	75,196	D
Common Stock	11/03/2025		S		246(1)	D	$1,029.45(13)	74,950	D
Common Stock	11/03/2025		S		210(1)	D	$1,030	74,740	D
Common Stock	11/03/2025		S		17(1)	D	$1,031.86	74,723	D
Common Stock	11/03/2025		S		184(1)	D	$1,032.07(14)	74,539	D
Common Stock	11/03/2025		S		80(1)	D	$1,033	74,459	D
Common Stock	11/03/2025		S		40(1)	D	$1,034.99	74,419	D
Common Stock	11/03/2025		S		40(1)	D	$1,035.25	74,379	D
Common Stock	11/03/2025		S		47(1)	D	$1,038.41(15)	74,332	D
Common Stock								5,331	I	Irrevocable Trust FBO Sarah N. Blegen
Common Stock								5,331	I	Irrevocable Trust FBO Theodore F. Blegen

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. These transactions were made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on 2/26/2025.

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 $1,013.45 to $1,013.75. 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 $1,014.12 to $1,014.64. 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 $1,016.43 to $1,016.59. 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 $1,019.10 to $1,019.68. 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 $1,020.20 to $1,020.40. 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 $1,021.04 to $1,021.32. 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 $1,023.07 to $1,023.98. 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.

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 $1,024.02 to $1,024.99. 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.

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 $1,025.00 to $1,025.98. 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.

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 $1,027.03 to $1,027.89. 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 $1,028.00 to $1,028.85. 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.

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 $1,029.14 to $1,029.77. 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 $1,032.00 to $1,032.18. 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 $1,038.40 to $1,038.42. 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. Bernie Blegen	11/04/2025
	** 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.