MONOLITHIC POWER SYSTEMS INC — Director's Dealing 2012

May 2, 2012

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: MONOLITHIC POWER SYSTEMS INC (MPWR)
CIK: 0001280452
Period of Report: 2012-04-30

Reporting Person: Rao Meera (CFO)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2012-04-30	Common Stock	M	11400.0	$13.53	Acquired	113908.0	Direct
2012-04-30	Common Stock	S	11400.0	$21.0122	Disposed	102508.0	Direct
2012-05-01	Common Stock	M	17100.0	$13.53	Acquired	119608.0	Direct
2012-05-01	Common Stock	S	17100.0	$21.9544	Disposed	102508.0	Direct
2012-05-02	Common Stock	S	1379.0	$21.002	Disposed	101129.0	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2012-04-30	Non-Qualified Stock Option (right to buy)	$13.53	M	11400.0	Disposed	2016-01-05	Common Stock (11400.0)	Direct
2012-05-01	Non-Qualified Stock Option (right to buy)	$13.53	M	17100.0	Disposed	2016-01-05	Common Stock (17100.0)	Direct

Footnotes

F1: In accordance with the reporting person's 10b5-1 trading plan.

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 $21.00 to $21.05. 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 $21.52 to $22.36. 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: Shares sold to pay tax obligations resulting from the vesting of restricted stock units.