X0306 4 2021-08-16 0001280452 MONOLITHIC POWER SYSTEMS INC MPWR 0001308647 Xiao Deming 5808 LAKE WASHINGTON BLVD NE KIRKLAND WA 98033 false true false false Pres. of MPS Asia Operations Common Stock 2021-08-16 4 J false 29 323.24 A 303727 D Common Stock 2021-08-19 4 S false 4739 462.00 D 298988 D Common Stock 1101 I by Spouse Shares acquired through the Company's qualified ESPP program. 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 $462.00 to $462.04. 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. /s/ Saria Tseng, attorney-in-fact for Mr. Deming Xiao 2021-08-23