=== SEC Form 4 — Statement of Changes in Beneficial Ownership ===
Document Type: 4
Period of Report: 2026-02-10
10b5-1 Pre-arranged Plan: Yes
--- Issuer ---
Name: MONOLITHIC POWER SYSTEMS INC (MPWR)
CIK: 0001280452
--- Reporting Owner ---
Name: Hsing Michael
CIK: 0001308676
Role: Director, Officer (CEO)
--- Non-Derivative Transactions ---
[Transaction #1]
Security: Common Stock
Date: 2026-02-10 | Code: S (Open market sale)
Shares: -4,302 | Price: $1,132.01
Total Value: $4,869,907.02
Shares Owned After: 983,932 | Ownership: D (Direct)
Footnotes:
[F1] These transactions were made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on 08/28/2025.
[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 $1,128.88 to $1,133.86. 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.
[Transaction #2]
Security: Common Stock
Date: 2026-02-10 | Code: S (Open market sale)
Shares: -6,325 | Price: $1,136.75
Total Value: $7,189,943.75
Shares Owned After: 977,607 | Ownership: D (Direct)
Footnotes:
[F1] These transactions were made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on 08/28/2025.
[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 $1,133.92 to $1,138.90. 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.
[Transaction #3]
Security: Common Stock
Date: 2026-02-10 | Code: S (Open market sale)
Shares: -16,080 | Price: $1,141.88
Total Value: $18,361,430.40
Shares Owned After: 961,527 | Ownership: D (Direct)
Footnotes:
[F1] These transactions were made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on 08/28/2025.
[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 $1,138.96 to $1,143.96. 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.
[Transaction #4]
Security: Common Stock
Date: 2026-02-10 | Code: S (Open market sale)
Shares: -3,864 | Price: $1,145.90
Total Value: $4,427,757.60
Shares Owned After: 957,663 | Ownership: D (Direct)
Footnotes:
[F1] These transactions were made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on 08/28/2025.
[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 $1,144.03 to $1,149.00. 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.
[Transaction #5]
Security: Common Stock
Date: 2026-02-10 | Code: S (Open market sale)
Shares: -1,215 | Price: $1,151.11
Total Value: $1,398,598.65
Shares Owned After: 956,448 | Ownership: D (Direct)
Footnotes:
[F1] These transactions were made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on 08/28/2025.
[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 $1,149.04 to $1,154.00. 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.
[Transaction #6]
Security: Common Stock
Date: 2026-02-10 | Code: S (Open market sale)
Shares: -694 | Price: $1,154.96
Total Value: $801,542.24
Shares Owned After: 955,754 | Ownership: D (Direct)
Footnotes:
[F1] These transactions were made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on 08/28/2025.
[F7] 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 $1,154.09 to $1,155.86. 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.
[Transaction #7]
Security: Common Stock
Date: 2026-02-10 | Code: S (Open market sale)
Shares: -360 | Price: $1,161.41
Total Value: $418,107.60
Shares Owned After: 955,394 | Ownership: D (Direct)
Footnotes:
[F1] These transactions were made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on 08/28/2025.
[F8] 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 $1,159.96 to $1,163.96. 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.
[Transaction #8]
Security: Common Stock
Date: 2026-02-10 | Code: S (Open market sale)
Shares: -880 | Price: $1,176.04
Total Value: $1,034,915.20
Shares Owned After: 954,514 | Ownership: D (Direct)
Footnotes:
[F1] These transactions were made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on 08/28/2025.
[F9] 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 $1,172.65 to $1,177.08. 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.
[Transaction #9]
Security: Common Stock
Date: 2026-02-10 | Code: S (Open market sale)
Shares: -280 | Price: $1,197.26
Total Value: $335,232.80
Shares Owned After: 954,234 | Ownership: D (Direct)
Footnotes:
[F1] These transactions were made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on 08/28/2025.
--- Holdings ---
[Holding #1]
Security: Common Stock
Ownership: I (Indirect)
[Holding #2]
Security: Common Stock
Ownership: I (Indirect)
--- Footnotes (Complete Index) ---
F1: These transactions were made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on 08/28/2025.
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 $1,128.88 to $1,133.86. 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.
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 $1,133.92 to $1,138.90. 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.
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 $1,138.96 to $1,143.96. 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.
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 $1,144.03 to $1,149.00. 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.
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 $1,149.04 to $1,154.00. 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.
F7: 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 $1,154.09 to $1,155.86. 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.
F8: 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 $1,159.96 to $1,163.96. 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.
F9: 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 $1,172.65 to $1,177.08. 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.
--- Signature ---
/s/ /s/ Saria Tseng, attorney-in-fact for Mr. Michael R. Hsing (2026-02-12)
