[Form 4] Monolithic Power Systems, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Theodore Blegen, EVP and CFO of Monolithic Power Systems (MPWR), reported multiple sales of common stock on 09/02/2025 under a Rule 10b5-1 trading plan adopted 02/26/2025. The Form 4 lists a series of dispositions at prices ranging roughly from $803.43 to $822.59, with weighted-average prices disclosed for several grouped lines. The reported transactions total 3,000 shares sold across multiple sale lots. Following these transactions the filing shows 40,939 shares held directly and two indirect holdings of 5,331 shares each in irrevocable trusts. The form was signed by an attorney-in-fact on behalf of Mr. Blegen.

Positive

• Sales conducted under a Rule 10b5-1 trading plan, indicating pre-planned transactions
• Detailed weighted-average prices provided for grouped trades, improving transparency
• Reporter retains substantial direct ownership (40,939 shares) and indirect trust holdings (5,331 shares each)

Negative

• Insider disposed of 3,000 shares on 09/02/2025
• Sale prices ranged between approximately $803.43 and $822.59, which are realized exits from insider holdings

Insights

Securities Analyst

TL;DR: Routine, pre-planned insider sales totaling 3,000 shares under a 10b5-1 plan; no new material disclosures.

The transactions are sales executed under a Rule 10b5-1 plan adopted on 02/26/2025, which indicates pre-scheduled dispositions rather than opportunistic trading. The Form 4 provides per-line weighted-average prices for grouped trades and shows the reporter retains significant direct holdings (40,939 shares) plus indirect trust holdings (5,331 shares each). There is no indication in the filing of additional derivative activity or changes in beneficial ownership other than the reported sales.

Corporate Governance Expert

TL;DR: Governance procedures appear followed: sales via authorized 10b5-1 plan and reporting executed by attorney-in-fact.

The filing documents compliance with Rule 10b5-1 and contains explanatory notes providing weighted-average prices and price ranges for grouped sales. The use of an attorney-in-fact signature is noted. The disclosure lists both direct and indirect ownership positions in irrevocable trusts. No executive departures, grants, or other governance actions are disclosed here.

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)
09/02/2025

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	09/02/2025		S		100(1)	D	$803.43	43,839	D
Common Stock	09/02/2025		S		100(1)	D	$804.64	43,739	D
Common Stock	09/02/2025		S		200(1)	D	$806.57(2)	43,539	D
Common Stock	09/02/2025		S		100(1)	D	$808.53(3)	43,439	D
Common Stock	09/02/2025		S		500(1)	D	$811.45(4)	42,939	D
Common Stock	09/02/2025		S		100(1)	D	$812.84	42,839	D
Common Stock	09/02/2025		S		100(1)	D	$813.09	42,739	D
Common Stock	09/02/2025		S		200(1)	D	$814.75(5)	42,539	D
Common Stock	09/02/2025		S		400(1)	D	$815.39(6)	42,139	D
Common Stock	09/02/2025		S		574(1)	D	$816.47(7)	41,565	D
Common Stock	09/02/2025		S		100(1)	D	$818.44	41,465	D
Common Stock	09/02/2025		S		200(1)	D	$820.7(8)	41,265	D
Common Stock	09/02/2025		S		200(1)	D	$821.75(9)	41,065	D
Common Stock	09/02/2025		S		126(1)	D	$822.59(10)	40,939	D
Common Stock								5,331	I	Irrevocable Trust FBO Theodore F. Blegen
Common Stock								5,331	I	Irrevocable Trust FBO Sarah N. 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 $806.25 to $806.89. 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.

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 $808.38 to $808.63. 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 $811.11 to $811.96. 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.

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 $814.61 to $814.88. 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.

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 $815.10 to $815.74. 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.

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 $816.20 to $816.76. 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 $820.50 to $820.88. 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.

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 $821.64 to $821.86. 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 $822.31 to $822.72. 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	09/02/2025
	** 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 did MPWR insider Theodore Blegen report on Form 4?

The Form 4 reports multiple sales of common stock by Theodore Blegen on 09/02/2025 executed under a Rule 10b5-1 plan.

How many shares did Mr. Blegen sell and when?

The filing shows dispositions totaling 3,000 shares sold on 09/02/2025.

Under what plan were the MPWR sales executed?

The transactions were made pursuant to a Rule 10b5-1 trading plan adopted on 02/26/2025.

What holdings does Mr. Blegen retain after the sales?

The Form 4 shows 40,939 shares held directly and two indirect holdings of 5,331 shares each in irrevocable trusts.

Were prices disclosed for the MPWR insider sales?

Yes. The report lists sale prices ranging from about $803.43 to $822.59, with weighted-average prices provided for grouped lines.