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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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<SEC-DOCUMENT>0001181431-04-045152.txt : 20040928
<SEC-HEADER>0001181431-04-045152.hdr.sgml : 20040928
<ACCEPTANCE-DATETIME>20040928133723
ACCESSION NUMBER:		0001181431-04-045152
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20040926
FILED AS OF DATE:		20040928
DATE AS OF CHANGE:		20040928

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			PETERSON JAMES J
		CENTRAL INDEX KEY:			0001192204

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-08866
		FILM NUMBER:		041049277

	MAIL ADDRESS:	
		STREET 1:		MICROSEMI CORP
		STREET 2:		2381 MORSE AVE
		CITY:			IRVINE
		STATE:			CA
		ZIP:			92614

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MICROSEMI CORP
		CENTRAL INDEX KEY:			0000310568
		STANDARD INDUSTRIAL CLASSIFICATION:	SEMICONDUCTORS & RELATED DEVICES [3674]
		IRS NUMBER:				952110371
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			0930

	BUSINESS ADDRESS:	
		STREET 1:		2381 MORSE AVENUE
		CITY:			IRVINE
		STATE:			CA
		ZIP:			92614
		BUSINESS PHONE:		7149798220

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	MICROSEMICONDUCTOR CORP
		DATE OF NAME CHANGE:	19830323
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>rrd53348.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2004-09-26</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000310568</issuerCik>
        <issuerName>MICROSEMI CORP</issuerName>
        <issuerTradingSymbol>MSCC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001192204</rptOwnerCik>
            <rptOwnerName>PETERSON JAMES J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>2381 MORSE AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>IRVINE</rptOwnerCity>
            <rptOwnerState></rptOwnerState>
            <rptOwnerZipCode>92614</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President &amp; CEO &amp; Director</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>ISO Option to Buy Common Stock</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>13.72</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2004-09-26</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>270000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>13.72</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2005-09-26</value>
            </exerciseDate>
            <expirationDate>
                <value>2014-09-26</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>270000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>913768</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">This incentive stock option was granted pursuant to Microsemi Corporation's 1987 Stock Plan, which satisfies the requirements of Rule 16b-3.  The option becomes exercisable in four equal installments, commencing one year after the date of the grant.</footnote>
        <footnote id="F2">Currently own 85,852 Shares of Microsemi Common Stock.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Debbie Weber, Attorney-in-Fact for James J. Peterson</signatureName>
        <signatureDate>2004-09-28</signatureDate>
    </ownerSignature>
</ownershipDocument>

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