[Form 4] MONOLITHIC POWER SYSTEMS INC Insider Trading Activity

Rhea-AI Filing Summary

Saria Tseng, EVP & General Counsel of Monolithic Power Systems, reported a sale of 14,510 shares of the company's common stock on 09/18/2025 at a price of $914.45 per share. The filing notes the sale was made pursuant to a Rule 10b5-1 trading plan adopted on 08/30/2024. After the reported transaction, the filing shows beneficial ownership of 144,494 shares, which includes 27 shares acquired through the company's qualified ESPP on 02/17/2025. The form is signed by the reporting person and discloses the relationship to the issuer as an officer.

Positive

• Sale executed under Rule 10b5-1 plan, indicating the transaction was pre-established and intended to meet affirmative defense requirements
• Full disclosure of transaction details including number of shares sold, sale price, execution date, and post-transaction beneficial ownership
• Includes ESPP disclosure specifying 27 shares acquired on 02/17/2025, which clarifies part of the ending balance

Negative

• Reduction in insider holdings: direct beneficial ownership decreased by 14,510 shares following the sale

Insights

Financial Analyst

TL;DR: Officer sold shares under a pre-established 10b5-1 plan; ownership remains substantial at 144,494 shares.

The reported transaction is a non-derivative disposition of 14,510 common shares executed under a Rule 10b5-1 trading plan, which typically indicates pre-planned, rule-compliant sales rather than opportunistic trading. The filing provides explicit figures for shares sold, execution date, sale price, and ending beneficial ownership, allowing clear quantification of change in insider holdings. No additional company financial data or context is provided in this Form 4 to assess impact on valuation or signaling beyond the change in insider holdings.

Corporate Governance Expert

TL;DR: Disclosure follows Section 16 requirements and cites a 10b5-1 plan, indicating procedural compliance.

The Form 4 identifies the reporting person as EVP & General Counsel and documents the sale date, price, and that the sale was executed pursuant to a 10b5-1 plan adopted 08/30/2024. The filing also records inclusion of 27 ESPP shares in the ending balance. These elements demonstrate adherence to insider-trading disclosure rules and provide necessary transparency for shareholders and regulators. The filing does not include any amendments or additional arrangements beyond the 10b5-1 plan mention.

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^*

Tseng Saria

(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 & General Counsel

3. Date of Earliest Transaction (Month/Day/Year)
09/18/2025

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	09/18/2025		S		14,510(1)	D	$914.45	144,494(2)	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 (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. This transaction was made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on 8/30/2024.

2. Ending balance includes 27 shares acquired on February 17, 2025 through the Company's qualified ESPP program.

Remarks:

	/s/ Saria Tseng	09/18/2025
	** 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 Saria Tseng report on Form 4?

The filing reports a sale of 14,510 shares on 09/18/2025 at $914.45 per share, executed under a Rule 10b5-1 trading plan.

Was the sale by Saria Tseng part of a 10b5-1 trading plan?

Yes. The Form 4 states the transaction was made pursuant to a Rule 10b5-1 trading plan adopted on 08/30/2024.

How many MPWR shares does Saria Tseng beneficially own after the transaction?

The Form 4 reports an ending beneficial ownership of 144,494 shares after the reported sale.

Does the Form 4 disclose any ESPP purchases for the reporting person?

Yes. The ending balance includes 27 shares acquired through the company's qualified ESPP on 02/17/2025.

What role does Saria Tseng hold at Monolithic Power Systems?

The Form 4 identifies Saria Tseng as an EVP & General Counsel of Monolithic Power Systems.