=== SEC Form 4 — Statement of Changes in Beneficial Ownership ===
Document Type: 4
Period of Report: 2026-02-11
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: 2026-02-11 | Code: S (Open market sale)
Shares: -363 | Price: $1,158.71
Total Value: $420,611.73
Shares Owned After: 953,871 | Ownership: D (Direct)
Footnotes:
[F1] These transactions were made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on 8/25/2025.
[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 $1,155.64 to $1,160.62 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: 2026-02-11 | Code: S (Open market sale)
Shares: -1,366 | Price: $1,163.71
Total Value: $1,589,627.86
Shares Owned After: 952,505 | Ownership: D (Direct)
Footnotes:
[F1] These transactions were made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on 8/25/2025.
[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 $1,160.70 to $1,165.64 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.
[Transaction #3]
Security: Common Stock
Date: 2026-02-11 | Code: S (Open market sale)
Shares: -1,533 | Price: $1,167.62
Total Value: $1,789,961.46
Shares Owned After: 950,972 | Ownership: D (Direct)
Footnotes:
[F1] These transactions were made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on 8/25/2025.
[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 $1,166.00 to $1,169.96. 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: 2026-02-11 | Code: S (Open market sale)
Shares: -1,987 | Price: $1,172.92
Total Value: $2,330,592.04
Shares Owned After: 948,985 | Ownership: D (Direct)
Footnotes:
[F1] These transactions were made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on 8/25/2025.
[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 $1,170.10 to $1,175.09. 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: 2026-02-11 | Code: S (Open market sale)
Shares: -2,799 | Price: $1,177.67
Total Value: $3,296,298.33
Shares Owned After: 946,186 | Ownership: D (Direct)
Footnotes:
[F1] These transactions were made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on 8/25/2025.
[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 $1,175.27 to $1,180.19. 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.
[Transaction #6]
Security: Common Stock
Date: 2026-02-11 | Code: S (Open market sale)
Shares: -1,542 | Price: $1,182.82
Total Value: $1,823,908.44
Shares Owned After: 944,644 | Ownership: D (Direct)
Footnotes:
[F1] These transactions were made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on 8/25/2025.
[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 $1,180.29 to $1,185.29. 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.
[Transaction #7]
Security: Common Stock
Date: 2026-02-11 | Code: S (Open market sale)
Shares: -2,104 | Price: $1,188.17
Total Value: $2,499,909.68
Shares Owned After: 942,540 | Ownership: D (Direct)
Footnotes:
[F1] These transactions were made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on 8/25/2025.
[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 $1,185.33 to $1,190.26. 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.
[Transaction #8]
Security: Common Stock
Date: 2026-02-11 | Code: S (Open market sale)
Shares: -6,079 | Price: $1,192.67
Total Value: $7,250,240.93
Shares Owned After: 936,461 | Ownership: D (Direct)
Footnotes:
[F1] These transactions were made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on 8/25/2025.
[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 $1,190.39 to $1,195.37. 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: 2026-02-11 | Code: S (Open market sale)
Shares: -14,578 | Price: $1,197.20
Total Value: $17,452,781.60
Shares Owned After: 921,883 | Ownership: D (Direct)
Footnotes:
[F1] These transactions were made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on 8/25/2025.
[F10] 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 $1,195.44 to $1,200.37. 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 #10]
Security: Common Stock
Date: 2026-02-11 | Code: S (Open market sale)
Shares: -649 | Price: $1,202.28
Total Value: $780,279.72
Shares Owned After: 921,234 | Ownership: D (Direct)
Footnotes:
[F1] These transactions were made pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on 8/25/2025.
[F11] 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 $1,200.46 to $1,203.86. 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.
--- 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 8/25/2025.
F10: 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 $1,195.44 to $1,200.37. 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.
F11: 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 $1,200.46 to $1,203.86. 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.
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 $1,155.64 to $1,160.62 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 $1,160.70 to $1,165.64 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.
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 $1,166.00 to $1,169.96. 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 $1,170.10 to $1,175.09. 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 $1,175.27 to $1,180.19. 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.
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 $1,180.29 to $1,185.29. 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.
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 $1,185.33 to $1,190.26. 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.
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 $1,190.39 to $1,195.37. 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 (2026-02-13)
