144 0001445300 XXXXXXXX LIVE 0001280452 MONOLITHIC POWER SYSTEMS INC 000-51026 1555 PALM BEACH LAKES BLVD. WEST PALM BEACH FL 33401 561-839-3999 DEAN ROBERT W II Officer Common Stock Morgan Stanley Smith Barney LLC Executive Financial Services

1 New York Plaza 8th Floor New York NY 10004

4 6253.12 49139853 05/18/2026 NASDAQ Common Stock 05/15/2026 Time-based restricted stock units Issuer N 4 05/15/2026 N/A N Robert Dean

1555 PALM BEACH LAKESBLVD. WEST PALM BEACH FL 98033

Common Stock 02/23/2026 85 101787.00 05/18/2026 /s/ Robert Dean