=== SEC Form 4 — Statement of Changes in Beneficial Ownership ===
Document Type: 4
Period of Report: 2026-05-06
10b5-1 Pre-arranged Plan: No
--- Issuer ---
Name: MONOLITHIC POWER SYSTEMS INC (MPWR)
CIK: 0001280452
--- Reporting Owner ---
Name: Elmiger Eugen J
CIK: 0001560945
Role: Director
--- Non-Derivative Transactions ---
[Transaction #1]
Security: Common Stock
Date: 2026-05-06 | Code: S (Open market sale)
Shares: -320 | Price: $1,559.88
Total Value: $499,161.60
Shares Owned After: 17,082 | Ownership: D (Direct)
Footnotes:
[F1] 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 $1,557.08 to $1,561.97. 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: 2026-05-06 | Code: S (Open market sale)
Shares: -814 | Price: $1,566.36
Total Value: $1,275,017.04
Shares Owned After: 16,268 | Ownership: D (Direct)
Footnotes:
[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 $1,563.39 to $1,568.28. 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: 2026-05-06 | Code: S (Open market sale)
Shares: -1,078 | Price: $1,571.58
Total Value: $1,694,163.24
Shares Owned After: 15,190 | Ownership: D (Direct)
Footnotes:
[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 $1,568.78 to $1,573.40. 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.
[Transaction #4]
Security: Common Stock
Date: 2026-05-06 | Code: S (Open market sale)
Shares: -834 | Price: $1,575.57
Total Value: $1,314,025.38
Shares Owned After: 14,356 | Ownership: D (Direct)
Footnotes:
[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 $1,573.86 to $1,578.73. 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: 2026-05-06 | Code: S (Open market sale)
Shares: -1,879 | Price: $1,581.81
Total Value: $2,972,220.99
Shares Owned After: 12,477 | Ownership: D (Direct)
Footnotes:
[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 $1,578.85 to $1,583.66. 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: 2026-05-06 | Code: S (Open market sale)
Shares: -2,587 | Price: $1,586.81
Total Value: $4,105,077.47
Shares Owned After: 9,890 | Ownership: D (Direct)
Footnotes:
[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 $1,583.79 to $1,588.65. 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.
[Transaction #7]
Security: Common Stock
Date: 2026-05-06 | Code: S (Open market sale)
Shares: -1,355 | Price: $1,591.38
Total Value: $2,156,319.90
Shares Owned After: 8,535 | Ownership: D (Direct)
Footnotes:
[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 $1,588.80 to $1,593.63. 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: 2026-05-06 | Code: S (Open market sale)
Shares: -2,619 | Price: $1,596.42
Total Value: $4,181,023.98
Shares Owned After: 5,916 | Ownership: D (Direct)
Footnotes:
[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 $1,593.95 to $1,598.78. 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: 2026-05-06 | Code: S (Open market sale)
Shares: -514 | Price: $1,600.14
Total Value: $822,471.96
Shares Owned After: 5,402 | Ownership: D (Direct)
Footnotes:
[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 $1,598.99 to $1,602.68 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.
--- Footnotes (Complete Index) ---
F1: 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 $1,557.08 to $1,561.97. 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 $1,563.39 to $1,568.28. 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 $1,568.78 to $1,573.40. 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.
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 $1,573.86 to $1,578.73. 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 $1,578.85 to $1,583.66. 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 $1,583.79 to $1,588.65. 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.
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 $1,588.80 to $1,593.63. 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 $1,593.95 to $1,598.78. 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 $1,598.99 to $1,602.68 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. Eugen J. Elmiger (2026-05-08)
