MONOLITHIC POWER SYSTEMS INC — Director's Dealing 2013

Feb 22, 2013

SEC Form 4 — Statement of Changes in Beneficial Ownership

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

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

Non-Derivative Transactions

Date	Security	Code	Shares	Price	A/D	Holdings After	Ownership
2013-02-15	Common Stock	J	1188.0	$17.884	Acquired	158499	Direct
2013-02-20	Common Stock	M	100.0	$10.91	Acquired	158599	Direct
2013-02-20	Common Stock	S	100.0	$25.52	Disposed	158499	Direct
2013-02-20	Common Stock	S	3107.0	$25.5413	Disposed	155392	Direct
2013-02-05	Common Stock	A	3000.0	$0.0	Acquired	12480	Indirect
2013-02-15	Common Stock	J	305.0	$17.884	Acquired	12822	Indirect

Derivative Transactions

Date	Security	Exercise Price	Code	Shares	A/D	Expiration	Underlying	Ownership
2013-02-20	Incentive Stock Option (right to buy)	$10.91	M	100.0	Disposed	2014-12-07	Common Stock (100)	Direct

Footnotes

F1: Acquired through the Company's qualified ESPP program.

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 $25.52 to $25.5601. 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: This report has been filed late due to an inadvertent administrative error.

F4: 1/16 of the Restricted Stock Units shall vest quarterly following the Vesting Commencement Date, provided that the Grantee continues to be a Service Provider from the Grant Date through each applicable vesting date.