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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 MY1U7KPczKNYSYMAhf45LH6nXiamCGVpApsY60zkGlypXyXgT17WEDV3g5h3Iqei
 Org5FxgayOKSUg3wKXgJFg==

<SEC-DOCUMENT>0001181431-04-053989.txt : 20041118
<SEC-HEADER>0001181431-04-053989.hdr.sgml : 20041118
<ACCEPTANCE-DATETIME>20041118170449
ACCESSION NUMBER:		0001181431-04-053989
CONFORMED SUBMISSION TYPE:	3
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20041118
FILED AS OF DATE:		20041118
DATE AS OF CHANGE:		20041118

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MONOLITHIC POWER SYSTEMS INC
		CENTRAL INDEX KEY:			0001280452
		STANDARD INDUSTRIAL CLASSIFICATION:	SEMICONDUCTORS & RELATED DEVICES [3674]
		IRS NUMBER:				770466789
		STATE OF INCORPORATION:			CA
		FISCAL YEAR END:			1231

	MAIL ADDRESS:	
		STREET 1:		983 UNIVERSITY AVE
		STREET 2:		BLDG A
		CITY:			LOS GATOS
		STATE:			CA
		ZIP:			95032

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			EARHART ALAN L
		CENTRAL INDEX KEY:			0001246846

	FILING VALUES:
		FORM TYPE:		3
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-51026
		FILM NUMBER:		041155549

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		408-944-4460

	MAIL ADDRESS:	
		STREET 1:		C/O QUANTUM CORPORATION
		STREET 2:		1650 TECHNOLOGY DRIVE, SUITE 800
		CITY:			SAN JOSE
		STATE:			CA
		ZIP:			95110
</SEC-HEADER>
<DOCUMENT>
<TYPE>3
<SEQUENCE>1
<FILENAME>rrd58352.xml
<DESCRIPTION>FORM 3
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2004-11-18</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001280452</issuerCik>
        <issuerName>MONOLITHIC POWER SYSTEMS INC</issuerName>
        <issuerTradingSymbol>MPWR</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001246846</rptOwnerCik>
            <rptOwnerName>EARHART ALAN L</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O MONOLITHIC POWER SYSTEMS, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>983 UNIVERSITY AVENUE, BUILDING A</rptOwnerStreet2>
            <rptOwnerCity>LOS GATOS</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>95032</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Option (Right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>7.50</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2005-09-17</value>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2014-09-17</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>30000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">50% of the shares subject to the option vest on 9/17/05; the remaining 50% of the shares subject to the option vest on 9/17/06.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Alan Earhart</signatureName>
        <signatureDate>2004-11-18</signatureDate>
    </ownerSignature>
</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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