Monolithic Power (NASDAQ: MPWR) EVP sells 8,963 shares under Rule 10b5-1 plan

Filing Impact

(Very High)

Filing Sentiment

(Very Negative)

Form Type

Rhea-AI Filing Summary

Monolithic Power Systems EVP & General Counsel Saria Tseng reported open-market sales of 8,963 shares of common stock on April 8, 2026 under a pre-arranged Rule 10b5-1 trading plan adopted on November 28, 2025. Sale prices included tranches at about $1,266.48 and $1,312.82 per share. After these transactions, she directly holds 156,983 shares and indirectly holds 1,000 shares through the C&T Discovery Foundation.

Insights

Pre-planned, modest-sized insider sale with substantial holdings retained.

EVP & General Counsel Saria Tseng sold 8,963 Monolithic Power Systems shares in multiple open-market trades on April 8, 2026. The filing explicitly states these transactions were executed under a Rule 10b5-1 trading plan adopted on November 28, 2025, indicating they were pre-scheduled rather than opportunistic.

Following the sales, Tseng still directly owns 156,983 shares and indirectly holds 1,000 shares via the C&T Discovery Foundation. Given the remaining position and the pre-planned nature of the trades, this looks like routine diversification or liquidity management rather than a major change in insider exposure. Future company filings may provide additional context on her overall equity compensation and ongoing trading plans.

Insider Trade Summary 10b5-1

Net Seller: 8,963 shares ($11,698,654)

Net Sell 11 txns

Insider Tseng Saria

Role EVP & General Counsel

Sold 8,963 shs ($11.70M)

Type	Security	Shares	Price	Value
Sale	Common Stock	560	$1,266.48	$709K
Sale	Common Stock	360	$1,270.29	$457K
Sale	Common Stock	240	$1,279.55	$307K
Sale	Common Stock	120	$1,287.12	$154K
Sale	Common Stock	400	$1,292.08	$517K
Sale	Common Stock	800	$1,302.52	$1.04M
Sale	Common Stock	1,279	$1,308.30	$1.67M
Sale	Common Stock	4,244	$1,312.82	$5.57M
Sale	Common Stock	840	$1,319.25	$1.11M
Sale	Common Stock	120	$1,321.94	$159K
holding	Common Stock	--	--	--

Holdings After Transaction: Common Stock — 165,386 shares (Direct); Common Stock — 1,000 shares (Indirect, C&T Discovery Foundation)

Footnotes (1)

These transactions were made pursuant to a Rule 10b5-1 trading plan adopted on 11/28/2025. 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 $1,264.04 to $1,268.56. 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 $1,269.36 to $1,272.23. 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 $1,277.78 to $1,281.49. 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 $1,284.26 to $1,289.24. 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 $1,290.95 to $1,294.78. 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 $1,299.99 to $1,304.82. 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 $1,305.08 to $1,310.00. 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 $1,310.27 to $1,315.08. 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 $1,316.25 to $1,321.04. 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 $1,321.50 to $1,322.56. 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.

Key Figures

Shares sold: 8,963 shares Example sale price: $1,266.48 per share Largest reported tranche: 4,244 shares +3 more

6 metrics

Shares sold 8,963 shares Total open-market sales on April 8, 2026

Example sale price $1,266.48 per share Tranche of 560 shares of common stock

Largest reported tranche 4,244 shares Sold at $1,312.82 per share

Direct holdings after sales 156,983 shares Common stock directly owned post-transaction

Indirect holdings 1,000 shares Indirectly owned through C&T Discovery Foundation

Trading plan adoption date November 28, 2025 Rule 10b5-1 plan governing the April 8, 2026 sales

Key Terms

Rule 10b5-1 trading plan, weighted average sale price, open-market sale, indirect, +1 more

5 terms

Rule 10b5-1 trading plan regulatory

"These transactions were made pursuant to a Rule 10b5-1 trading plan adopted on 11/28/2025."

A Rule 10b5-1 trading plan is a pre-arranged schedule that allows company insiders to buy or sell stock at specific times, even if they have inside information. It helps prevent accusations of unfair trading by making these transactions look planned and transparent, rather than sneaky or illegal.

weighted average sale price financial

"The price is the weighted average sale price for the transactions reported on this line."

open-market sale financial

"transaction_action: "open-market sale""

An open-market sale is when a shareholder sells existing shares directly on a public exchange to any willing buyer, rather than through a private deal. Think of it like putting goods on a busy market stall where price is set by supply and demand; for investors it matters because such sales increase available supply, can put short-term downward pressure on the stock price, and signal changes in liquidity or investor confidence.

indirect financial

"ownership_type: "indirect" with nature_of_ownership: "C&T Discovery Foundation""

non-derivative financial

"transaction_type: "non-derivative" for the common stock sales"

Form 4 Insider Transactions: What Each Field Means →

04/10/2026 - 12:46 PM

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^*

Tseng Saria

(Last)

(First)

(Middle)

1555 PALM BEACH LAKES BLVD.

(Street)

WEST PALM BEACH

FLORIDA

33401

(City)

(State)

(Zip)

UNITED STATES

(Country)

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

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
04/08/2026

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

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

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

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)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
Common Stock	04/08/2026		S		560⁽¹⁾	D	$1,266.48⁽²⁾	165,386	D
Common Stock	04/08/2026		S		360⁽¹⁾	D	$1,270.29⁽³⁾	165,026	D
Common Stock	04/08/2026		S		240⁽¹⁾	D	$1,279.55⁽⁴⁾	164,786	D
Common Stock	04/08/2026		S		120⁽¹⁾	D	$1,287.12⁽⁵⁾	164,666	D
Common Stock	04/08/2026		S		400⁽¹⁾	D	$1,292.08⁽⁶⁾	164,266	D
Common Stock	04/08/2026		S		800⁽¹⁾	D	$1,302.52⁽⁷⁾	163,466	D
Common Stock	04/08/2026		S		1,279⁽¹⁾	D	$1,308.3⁽⁸⁾	162,187	D
Common Stock	04/08/2026		S		4,244⁽¹⁾	D	$1,312.82⁽⁹⁾	157,943	D
Common Stock	04/08/2026		S		840⁽¹⁾	D	$1,319.25⁽¹⁰⁾	157,103	D
Common Stock	04/08/2026		S		120⁽¹⁾	D	$1,321.94⁽¹¹⁾	156,983	D
Common Stock								1,000	I	C&T Discovery Foundation

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)
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)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)

Explanation of Responses:

1. These transactions were made pursuant to a Rule 10b5-1 trading plan adopted on 11/28/2025.

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 $1,264.04 to $1,268.56. 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.

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 $1,269.36 to $1,272.23. 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 $1,277.78 to $1,281.49. 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 $1,284.26 to $1,289.24. 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 $1,290.95 to $1,294.78. 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 $1,299.99 to $1,304.82. 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 $1,305.08 to $1,310.00. 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 $1,310.27 to $1,315.08. 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 $1,316.25 to $1,321.04. 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 $1,321.50 to $1,322.56. 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.

Remarks:

	/s/ Saria Tseng	04/10/2026
	** 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.
* Form 4: SEC 1474 (03-26)

Source: View Original Filing on SEC EDGAR

FAQ

What did MPWR executive Saria Tseng report in the latest Form 4?

She reported selling 8,963 shares of Monolithic Power Systems common stock in multiple open-market transactions on April 8, 2026. These trades were made under a pre-arranged Rule 10b5-1 trading plan adopted in November 2025 and reflect routine insider activity.

At what prices did Saria Tseng sell MPWR shares on April 8, 2026?

The Form 4 shows weighted average sale prices including tranches at $1,266.48 and $1,312.82 per share. Footnotes explain each line’s price averages multiple trades within stated ranges, and detailed per-trade information is available upon request from the company or regulators.

How many MPWR shares does Saria Tseng hold after these transactions?

After the reported April 8, 2026 sales, Saria Tseng directly holds 156,983 shares of Monolithic Power Systems common stock. The filing also shows an additional 1,000 shares held indirectly through the C&T Discovery Foundation, reflecting a continued significant ownership position.

Was the MPWR insider sale by Saria Tseng under a Rule 10b5-1 plan?

Yes. A footnote states that all reported transactions were executed pursuant to a Rule 10b5-1 trading plan adopted on November 28, 2025. Such plans are pre-arranged, helping separate routine liquidity activity from discretionary trading decisions by corporate insiders.

Does the Form 4 show any derivative exercises or tax-withholding for MPWR?

No. The transaction summary indicates only non-derivative open-market sales totaling 8,963 shares, with zero derivative exercises, gifts, or tax-withholding entries. The derivative summary is empty, suggesting no option or other derivative transactions were reported in this particular filing.