Monolithic Power Systems (MPWR) CFO reports 10b5-1 stock sales on Form 4 filing

Rhea-AI Filing Summary

Monolithic Power Systems executive Theodore Blegen, EVP and CFO, reported planned stock sales under a Rule 10b5-1 trading plan. On January 2, 2026, he sold multiple small blocks of Monolithic Power Systems common stock at prices between $927.61 and $946.62 per share, as disclosed across several transaction lines. These trades were executed pursuant to a Rule 10b5-1 plan adopted on February 26, 2025, which allows pre-arranged sales according to preset instructions.

Following these transactions, Blegen directly held 68,332 shares of common stock. The filing also shows indirect beneficial ownership of 5,331 shares held in an irrevocable trust for Sarah N. Blegen and another 5,331 shares held in an irrevocable trust for Theodore F. Blegen, reflecting additional trust-related holdings associated with the reporting person.

Insider Trade Summary

Net Seller: 3,000 shares ($2,821,399)

Net Sell 17 txns

Insider BLEGEN THEODORE

Role EVP and CFO

Sold 3,000 shs ($2.82M)

Type	Security	Shares	Price	Value
Sale	Common Stock	80	$927.61	$74K
Sale	Common Stock	194	$930.86	$181K
Sale	Common Stock	80	$933.64	$75K
Sale	Common Stock	40	$934.74	$37K
Sale	Common Stock	80	$935.33	$75K
Sale	Common Stock	120	$936.50	$112K
Sale	Common Stock	460	$938.52	$432K
Sale	Common Stock	117	$939.75	$110K
Sale	Common Stock	40	$940.03	$38K
Sale	Common Stock	406	$941.60	$382K
Sale	Common Stock	74	$942.42	$70K
Sale	Common Stock	539	$943.71	$509K
Sale	Common Stock	650	$944.35	$614K
Sale	Common Stock	40	$945.00	$38K
Sale	Common Stock	80	$946.62	$76K
holding	Common Stock	--	--	--
holding	Common Stock	--	--	--

Holdings After Transaction: Common Stock — 71,252 shares (Direct); Common Stock — 5,331 shares (Indirect, Irrevocable Trust FBO Sarah N. Blegen)

Footnotes (1)

1. These transactions were made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on 2/26/2025. 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 $935.08 to $935.57. 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 $938.14 to $938.69. 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 $939.51 to $939.99. 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 $941.00 to $941.67. 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 $942.01 to $942.77. 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 $943.37 to $943.85. 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 $944.01 to $944.51. 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.

Form 4 Insider Transactions: What Each Field Means →

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^*

BLEGEN THEODORE

(Last) (First) (Middle)

1555 PALM BEACH LAKES BLVD.

(Street)

WEST PALM BEACH FL 33401

(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 and CFO

3. Date of Earliest Transaction (Month/Day/Year)
01/02/2026

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	01/02/2026		S		80(1)	D	$927.61	71,252	D
Common Stock	01/02/2026		S		194(1)	D	$930.86	71,058	D
Common Stock	01/02/2026		S		80(1)	D	$933.64	70,978	D
Common Stock	01/02/2026		S		40(1)	D	$934.74	70,938	D
Common Stock	01/02/2026		S		80(1)	D	$935.33(2)	70,858	D
Common Stock	01/02/2026		S		120(1)	D	$936.5	70,738	D
Common Stock	01/02/2026		S		460(1)	D	$938.52(3)	70,278	D
Common Stock	01/02/2026		S		117(1)	D	$939.75(4)	70,161	D
Common Stock	01/02/2026		S		40(1)	D	$940.03	70,121	D
Common Stock	01/02/2026		S		406(1)	D	$941.6(5)	69,715	D
Common Stock	01/02/2026		S		74(1)	D	$942.42(6)	69,641	D
Common Stock	01/02/2026		S		539(1)	D	$943.71(7)	69,102	D
Common Stock	01/02/2026		S		650(1)	D	$944.35(8)	68,452	D
Common Stock	01/02/2026		S		40(1)	D	$945	68,412	D
Common Stock	01/02/2026		S		80(1)	D	$946.62	68,332	D
Common Stock								5,331	I	Irrevocable Trust FBO Sarah N. Blegen
Common Stock								5,331	I	Irrevocable Trust FBO Theodore F. Blegen

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 by the reporting person on 2/26/2025.

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 $935.08 to $935.57. 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 $938.14 to $938.69. 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 $939.51 to $939.99. 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 $941.00 to $941.67. 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 $942.01 to $942.77. 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 $943.37 to $943.85. 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.

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 $944.01 to $944.51. 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, attorney-in-fact for Mr. Bernie Blegen	01/02/2026
	** 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.

FAQ

Who is the insider reporting this Form 4 for Monolithic Power Systems (MPWR)?

The Form 4 is filed by Theodore Blegen, who serves as Executive Vice President (EVP) and Chief Financial Officer (CFO) of Monolithic Power Systems, Inc.

What transactions did MPWR CFO Theodore Blegen report on January 2, 2026?

Blegen reported multiple open-market sales of Monolithic Power Systems common stock on January 2, 2026. Each line shows a small block of shares sold at prices ranging from $927.61 to $946.62 per share, all coded as “S” for sale of non-derivative securities.

How many Monolithic Power Systems shares does the CFO hold after these transactions?

After the reported sales on January 2, 2026, Theodore Blegen directly beneficially owned 68,332 shares of Monolithic Power Systems common stock. The filing also shows separate indirect positions in two irrevocable trusts.

What does the Rule 10b5-1 trading plan disclosure mean in this MPWR Form 4?

The footnotes state that these transactions were made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on February 26, 2025. A Rule 10b5-1 plan allows an insider to pre-arrange trades under preset instructions, which can help separate trading activity from day-to-day information they may possess.

At what prices were the Monolithic Power Systems shares sold by the CFO?

The reported sales occurred at various prices, including individual sale prices such as $927.61, $930.86, $933.64, $938.52, $941.60, $942.42, $943.71, $944.35, $945.00, and $946.62 per share. Several lines note that each reported price is a weighted average for trades within given price ranges.

What indirect holdings are reported for the MPWR CFO on this Form 4?

In addition to his direct holdings, the Form 4 lists indirect beneficial ownership of 5,331 shares of common stock held by an Irrevocable Trust FBO Sarah N. Blegen and 5,331 shares held by an Irrevocable Trust FBO Theodore F. Blegen.

Does this Form 4 involve any derivative securities of Monolithic Power Systems?

The filing includes a table for derivative securities, but no derivative transactions are reported in that section. All disclosed transactions for January 2, 2026 relate to non-derivative common stock sales and trust holdings.