MONOLITHIC POWER SYSTEMS INC — Director's Dealing 2013

May 6, 2013

SEC Form 4 — Statement of Changes in Beneficial Ownership

Issuer: MONOLITHIC POWER SYSTEMS INC (MPWR)
CIK: 0001280452
Period of Report: 2013-05-02

Reporting Person: Xiao Deming (Pres. of MPS Asia Operations)

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2013-05-02	Common Stock	S	1940.0	$23.171	Disposed	117265	Direct
2013-05-02	Common Stock	A	173.0	$0.0	Acquired	117438	Direct
2013-05-02	Common Stock	S	92.0	$23.17	Disposed	117346	Direct
2013-05-03	Common Stock	S	264.0	$24.18	Disposed	117082	Direct
2013-05-03	Common Stock	A	23.0	$0.0	Acquired	117105	Direct
2013-05-03	Common Stock	S	13.0	$24.18	Disposed	117092	Direct
2013-05-03	Common Stock	M	70000.0	$11.31	Acquired	187092	Direct
2013-05-03	Common Stock	S	70000.0	$24.2107	Disposed	117092	Direct

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2013-05-03	Non-Qualified Stock Option (right to buy)	$11.85	M	70000.0	Disposed	2013-10-26	Common Stock (70000)	Direct

Holdings (Non-Derivative)

Security	Shares	Ownership
Common Stock	12587	Indirect

Footnotes

F1: Shares sold to pay tax obligations resulting from the vesting of restricted stock units.

F2: Equitable stock dividend adjustment approved by the Board of Director as a result of dividend Payment to shareholders on December 28, 2012. Stock dividends will release according to the same vesting schedule as the original grants.

F3: On December 11, 2012, the Company's Board declared a special cash dividend of $1.00 per common share, which was paid on December 28, 2012 to all shareholders of record as of the close of business on December 21, 2012. The Board approved a modification whereby each outstanding option as of December 28, 2012 was increased by a ratio of 1.0471 with a corresponding reduction in the exercise price.