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

Yes. The filing states the transactions were made under a Rule 10b5-1 trading plan adopted on November 28, 2025. Such pre-arranged plans allow insiders to schedule trades in advance, reducing the impact of day-to-day information on trading decisions.

Monolithic Power (NASDAQ: MPWR) EVP Saria Tseng sells 25,674 shares

Filing Impact

(Very High)

Filing Sentiment

(Very Negative)

Form Type

Rhea-AI Filing Summary

Monolithic Power Systems EVP & General Counsel Saria Tseng reported selling a total of 25,674 shares of common stock in multiple open-market transactions on March 30, 2026. The weighted-average sale prices for these trades ranged from about $998 to $1,042 per share, as detailed in price-range footnotes.

The filing notes these transactions were executed under a pre-arranged Rule 10b5-1 trading plan adopted on November 28, 2025. After the sales, Tseng directly holds 174,982 shares and has an additional 1,000 shares held indirectly through the C&T Discovery Foundation.

Insider Trade Summary 10b5-1

Net Seller: 25,674 shares ($25,943,638)

Net Sell 9 txns

Insider Tseng Saria

Role EVP & General Counsel

Sold 25,674 shs ($25.94M)

Type	Security	Shares	Price	Value
Sale	Common Stock	5,154	$1,000.81	$5.16M
Sale	Common Stock	9,080	$1,005.18	$9.13M
Sale	Common Stock	3,360	$1,009.63	$3.39M
Sale	Common Stock	3,194	$1,017.22	$3.25M
Sale	Common Stock	2,200	$1,023.00	$2.25M
Sale	Common Stock	2,440	$1,029.21	$2.51M
Sale	Common Stock	166	$1,035.60	$172K
Sale	Common Stock	80	$1,041.12	$83K
holding	Common Stock	--	--	--

Holdings After Transaction: Common Stock — 195,502 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 $998.36 to $1,002.92. 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. Ending balance includes 30 shares acquired on February 17, 2026 through the Company's qualified ESPP program. 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 $1,003.06 to $1,007.85. 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. 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 $1,008.00 to $1,012.65. 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 $1,013.83 to $1,018.85. 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. 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 $1,020.71 to $1,025.36. 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 $1,027.37 to $1,032.40. 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. 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 $1,033.98 to $1,037.25. 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 $1,039.30 to $1,042.50. 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: 25,674 shares Lowest reported sale price: $998.36 per share Highest reported sale price: $1,042.50 per share +3 more

6 metrics

Shares sold 25,674 shares Aggregate open-market sales on March 30, 2026

Lowest reported sale price $998.36 per share Price range for first reported tranche

Highest reported sale price $1,042.50 per share Price range for final reported tranche

Direct holdings after sales 174,982 shares Direct ownership reported after transactions

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

Number of sale entries 8 transactions Non-derivative open-market sale lines in Form 4

Key Terms

Rule 10b5-1 trading plan, weighted average sale price, qualified ESPP program

3 terms

Rule 10b5-1 trading plan financial

"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."

qualified ESPP program financial

"Ending balance includes 30 shares acquired on February 17, 2026 through the Company's qualified ESPP program."

Form 4 Insider Transactions: What Each Field Means →

04/01/2026 - 06:41 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)
03/30/2026

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	03/30/2026		S		5,154⁽¹⁾	D	$1,000.81⁽²⁾	195,502⁽³⁾	D
Common Stock	03/30/2026		S		9,080⁽¹⁾	D	$1,005.18⁽⁴⁾	186,422	D
Common Stock	03/30/2026		S		3,360⁽¹⁾	D	$1,009.63⁽⁵⁾	183,062	D
Common Stock	03/30/2026		S		3,194⁽¹⁾	D	$1,017.22⁽⁶⁾	179,868	D
Common Stock	03/30/2026		S		2,200⁽¹⁾	D	$1,023⁽⁷⁾	177,668	D
Common Stock	03/30/2026		S		2,440⁽¹⁾	D	$1,029.21⁽⁸⁾	175,228	D
Common Stock	03/30/2026		S		166⁽¹⁾	D	$1,035.6⁽⁹⁾	175,062	D
Common Stock	03/30/2026		S		80⁽¹⁾	D	$1,041.12⁽¹⁰⁾	174,982	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 $998.36 to $1,002.92. 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. Ending balance includes 30 shares acquired on February 17, 2026 through the Company's qualified ESPP program.

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 $1,003.06 to $1,007.85. 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.

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 $1,008.00 to $1,012.65. 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 $1,013.83 to $1,018.85. 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.

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 $1,020.71 to $1,025.36. 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 $1,027.37 to $1,032.40. 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.

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 $1,033.98 to $1,037.25. 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 $1,039.30 to $1,042.50. 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	04/01/2026
	** 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?

Saria Tseng reported open-market sales of 25,674 Monolithic Power Systems shares on March 30, 2026. The trades were executed in multiple blocks, each with its own weighted-average price, and were carried out under a pre-arranged Rule 10b5-1 trading plan.

At what prices did MPWR shares trade in Saria Tseng’s Form 4 sales?

The sales used weighted-average prices that ranged from $998.36 to $1,042.50 per share. Each transaction line in the filing shows a specific average price, with footnotes providing the detailed price ranges for the underlying individual trades.

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

Following the reported transactions, Saria Tseng directly owns 174,982 shares of Monolithic Power Systems common stock. The filing also shows 1,000 additional shares held indirectly through the C&T Discovery Foundation, bringing total reported holdings to 175,982 shares.

Does the MPWR Form 4 show any derivative exercises for Saria Tseng?

No derivative transactions are listed in this Form 4. All eight reportable trades involve sales of Monolithic Power Systems common stock, and the derivative summary section shows no remaining derivative positions or recent option exercises in this particular filing.