Monolithic Power EVP sells 1,400 shares in plan

Monolithic Power Systems EVP & General Counsel Saria Tseng reported open-market sales of 1,400 shares of common stock on April 1, 2026.

Rhea-AI Filing Summary

Monolithic Power Systems EVP & General Counsel Saria Tseng reported open-market sales of 1,400 shares of common stock on April 1, 2026. The trades occurred in multiple blocks at weighted average prices ranging from about $1,130.82 to $1,137.71 per share under a pre-arranged Rule 10b5-1 trading plan adopted on November 28, 2025. After these transactions, she directly holds 173,582 shares and has an additional 1,000 shares reported as indirectly held through C&T Discovery Foundation.

Insider Trade Summary 10b5-1

Net Seller: 1,400 shares

Net Sell 6 txns

Insider Tseng Saria

Role EVP & General Counsel

Sold 1,400 shs ($1.59M)

Type	Security	Shares	Price	Value
Sale	Common Stock	576	$1,131.24	$652K
Sale	Common Stock	184	$1,132.15	$208K
Sale	Common Stock	160	$1,134.14	$181K
Sale	Common Stock	188	$1,135.91	$214K
Sale	Common Stock	292	$1,136.99	$332K
holding	Common Stock	--	--	--

Holdings After Transaction: Common Stock — 173,582 shares (Direct); Common Stock — 1,000 shares (Indirect, C&T Discovery Foundation)

Footnotes (6)

1. F1. These transactions were made pursuant to a Rule 10b5-1 trading plan adopted on 11/28/2025.
2. F2. 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 $1,130.82 to $1,131.76. 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.
3. F3. 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 $1,131.84 to $1,132.46. 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. F4. 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 $1,133.77 to $1,134.75. 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. F5. 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 $1,135.41 to $1,136.26. 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. F6. 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 $1,136.47 to $1,137.71. 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: 1,400 shares Lowest sale price range: $1,130.82–$1,131.76 Highest sale price range: $1,136.47–$1,137.71 +4 more

7 metrics

Shares sold 1,400 shares Total common shares sold on April 1, 2026

Lowest sale price range $1,130.82–$1,131.76 Weighted average price range for one sale line

Highest sale price range $1,136.47–$1,137.71 Weighted average price range for another sale line

Direct holdings after sales 173,582 shares Direct common stock ownership following transactions

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

Trading plan adoption date November 28, 2025 Adoption date of Rule 10b5-1 trading plan

Sale transactions count 5 transactions Number of non-derivative sale lines reported

Key Terms

Rule 10b5-1 trading plan, open-market sale, weighted average sale price, 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.

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.

weighted average sale price financial

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

indirect financial

""ownership_type": "indirect""

non-derivative financial

""transaction_type": "non-derivative""

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What did MPWR EVP & General Counsel Saria Tseng report in this Form 4?

She reported multiple open-market sales of Monolithic Power Systems common stock. On April 1, 2026, she sold a total of 1,400 shares in several transactions, all classified as sales of non-derivative common stock.

How many MPWR shares did Saria Tseng sell and at what prices?

She sold 1,400 shares of Monolithic Power Systems common stock. The weighted average sale prices for the reported trades ranged from approximately $1,130.82 to $1,137.71 per share, with each line item covering multiple individual trades within those price ranges.

How many Monolithic Power Systems (MPWR) shares does Saria Tseng hold after these sales?

Following the reported transactions, she directly owns 173,582 shares of Monolithic Power Systems common stock. The filing also shows an additional 1,000 shares reported as indirectly owned through C&T Discovery Foundation, reflecting a separate indirect holding.

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

Yes. A footnote states these transactions were made pursuant to a Rule 10b5-1 trading plan adopted on November 28, 2025. Such pre-arranged plans schedule trades in advance, providing structure around the timing of insider stock sales.

What indirect ownership in MPWR stock is disclosed for Saria Tseng?

The filing reports 1,000 shares of Monolithic Power Systems common stock as held indirectly through C&T Discovery Foundation. This indirect entry is classified as a holding, with ownership type marked as indirect rather than a new buy or sell transaction.

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

The Form 4 lists five separate non-derivative transactions coded “S,” each representing an open-market sale on April 1, 2026. Together, these sales total 1,400 shares of Monolithic Power Systems common stock across different price ranges.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Accepted by SEC EDGAR 04/03/2026 - 05:36 PM Learn about SEC filing dates

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)

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)
04/01/2026

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)
			Code	V	Amount	(A) or (D)	Price
Common Stock	04/01/2026		S		576(1)	D	$1,131.24(2)	174,406	D
Common Stock	04/01/2026		S		184(1)	D	$1,132.15(3)	174,222	D
Common Stock	04/01/2026		S		160(1)	D	$1,134.14(4)	174,062	D
Common Stock	04/01/2026		S		188(1)	D	$1,135.91(5)	173,874	D
Common Stock	04/01/2026		S		292(1)	D	$1,136.99(6)	173,582	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)
				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 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 $1,130.82 to $1,131.76. 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.

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 $1,131.84 to $1,132.46. 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 $1,133.77 to $1,134.75. 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 $1,135.41 to $1,136.26. 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 $1,136.47 to $1,137.71. 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	04/03/2026
	** 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)