MPWR (MPWR) EVP & General Counsel Tseng sells 7,636 shares under 10b5-1 plan

Filing Impact

(Very High)

Filing Sentiment

(Very Negative)

Form Type

Rhea-AI Filing Summary

MONOLITHIC POWER SYSTEMS INC executive Saria Tseng sold 7,636 shares of Common Stock in open-market transactions. The EVP & General Counsel executed eight planned sales on April 6, 2026 under a Rule 10b5-1 trading plan adopted on November 28, 2025, at prices such as $1,139.96, $1,170.38 and $1,179.50 per share. After these trades, Tseng holds 169,022 shares directly and 1,000 shares indirectly through C&T Discovery Foundation.

Insights

Routine planned sales by MPWR's EVP & General Counsel under a 10b5-1 plan.

Saria Tseng, EVP & General Counsel of MONOLITHIC POWER SYSTEMS INC, sold 7,636 shares of Common Stock on April 6, 2026 through eight open-market transactions. Sale prices included $1,139.96, $1,170.38 and $1,179.50 per share.

These dispositions were made under a pre-arranged Rule 10b5-1 trading plan adopted on November 28, 2025, which suggests the timing was scheduled rather than opportunistic. After the transactions, Tseng still directly owns 169,022 shares and indirectly holds 1,000 shares via C&T Discovery Foundation, indicating the sales represent a minority portion of her visible position.

Insider Trade Summary 10b5-1

Net Seller: 7,636 shares ($8,918,434)

Net Sell 9 txns

Insider Tseng Saria

Role EVP & General Counsel

Sold 7,636 shs ($8.92M)

Type	Security	Shares	Price	Value
Sale	Common Stock	244	$1,139.96	$278K
Sale	Common Stock	556	$1,144.42	$636K
Sale	Common Stock	480	$1,149.05	$552K
Sale	Common Stock	560	$1,159.62	$649K
Sale	Common Stock	684	$1,165.66	$797K
Sale	Common Stock	2,036	$1,170.38	$2.38M
Sale	Common Stock	1,680	$1,176.35	$1.98M
Sale	Common Stock	1,396	$1,179.50	$1.65M
holding	Common Stock	--	--	--

Holdings After Transaction: Common Stock — 173,338 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 $1,136.69 to $1,141.64. 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. 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 $1,141.91 to $ 1,146.02. 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 $1,147.58 to $1,152.19. 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 $1,156.58 to $1,161.42. 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. 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 $1,163.16 to $1,168.12. 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 $1,168.24 to $ 1,172.42. 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. 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 $1,173.31 to $1,178.29. 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 $1,178.53 to $1,180.83. 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: 7,636 shares Sample sale price: $1,139.96/share Sample sale price: $1,170.38/share +5 more

8 metrics

Shares sold 7,636 shares Total Common Stock sold on April 6, 2026

Sample sale price $1,139.96/share One open-market sale price on April 6, 2026

Sample sale price $1,170.38/share One open-market sale price on April 6, 2026

Sample sale price $1,179.50/share One open-market sale price on April 6, 2026

Direct holdings after sale 169,022 shares Direct MPWR Common Stock owned after transactions

Indirect holdings 1,000 shares Indirect MPWR shares via C&T Discovery Foundation

Sale transactions count 8 transactions Number of sale entries on April 6, 2026

Net buy/sell direction Net sell of 7,636 shares Transaction summary for this Form 4

Key Terms

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

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

non-derivative financial

"transaction_type": "non-derivative""

Form 4 Insider Transactions: What Each Field Means →

04/08/2026 - 01:42 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)
04/06/2026

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	04/06/2026		S		244⁽¹⁾	D	$1,139.96⁽²⁾	173,338	D
Common Stock	04/06/2026		S		556⁽¹⁾	D	$1,144.42⁽³⁾	172,782	D
Common Stock	04/06/2026		S		480⁽¹⁾	D	$1,149.05⁽⁴⁾	172,302	D
Common Stock	04/06/2026		S		560⁽¹⁾	D	$1,159.62⁽⁵⁾	171,742	D
Common Stock	04/06/2026		S		684⁽¹⁾	D	$1,165.66⁽⁶⁾	171,058	D
Common Stock	04/06/2026		S		2,036⁽¹⁾	D	$1,170.38⁽⁷⁾	169,022	D
Common Stock	04/06/2026		S		1,680⁽¹⁾	D	$1,176.35⁽⁸⁾	167,342	D
Common Stock	04/06/2026		S		1,396⁽¹⁾	D	$1,179.5⁽⁹⁾	165,946	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 $1,136.69 to $1,141.64. 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.

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 $1,141.91 to $ 1,146.02. 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 $1,147.58 to $1,152.19. 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 $1,156.58 to $1,161.42. 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.

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 $1,163.16 to $1,168.12. 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 $1,168.24 to $ 1,172.42. 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.

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 $1,173.31 to $1,178.29. 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 $1,178.53 to $1,180.83. 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	04/08/2026
	** 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 insider transaction did MPWR executive Saria Tseng report on this Form 4?

Saria Tseng reported selling 7,636 shares of MONOLITHIC POWER SYSTEMS INC Common Stock. The sales occurred on April 6, 2026 across eight open-market trades, with per-share prices including $1,139.96, $1,170.38 and $1,179.50, as shown in the Form 4 data.

At what prices did Saria Tseng sell MPWR shares in the April 6, 2026 transactions?

The reported MPWR share sales by Saria Tseng included prices such as $1,139.96, $1,170.38 and $1,179.50 per share. Footnotes describe these as weighted average sale prices for ranges of trades, with full breakdowns available upon request from regulatory or issuer contacts.

How many MPWR shares does Saria Tseng hold after the reported Form 4 sales?

After the April 6, 2026 trades, Saria Tseng directly owns 169,022 shares of MONOLITHIC POWER SYSTEMS INC Common Stock. She also has an indirect holding of 1,000 shares through C&T Discovery Foundation, according to the holding entry included in the Form 4 data.

Were Saria Tseng’s MPWR stock sales made under a Rule 10b5-1 trading plan?

Yes. A footnote states that the April 6, 2026 MPWR share sales by Saria Tseng were made pursuant to a Rule 10b5-1 trading plan adopted on November 28, 2025. Such plans pre-schedule trades, reducing the significance of short-term market timing.

How many separate sale transactions did the MPWR Form 4 report for Saria Tseng?

The Form 4 transaction summary shows eight sale transactions for Saria Tseng’s MPWR Common Stock on April 6, 2026. These open-market sales together totaled 7,636 shares, classified as non-derivative transactions in the filing’s transaction table.

Does the MPWR Form 4 show any option exercises or derivative trades by Saria Tseng?

No derivative exercises are listed in this Form 4. The derivative summary shows zero derivative transactions and zero exercise shares, indicating that the reported activity consists solely of non-derivative open-market sales of MPWR Common Stock on April 6, 2026.