<SUBMISSION>
<ACCESSION-NUMBER>0001285081-06-000090
<TYPE>4/A
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20061208
<FILING-DATE>20061214
<DATE-OF-FILING-DATE-CHANGE>20061214
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>Sayiner Necip
<CIK>0001338515
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4/A
<ACT>34
<FILE-NUMBER>000-29823
<FILM-NUMBER>061277724
</FILING-VALUES>
<BUSINESS-ADDRESS>
<PHONE>512-416-8500
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>400 W CESAR CHAVEZ
<CITY>AUSTIN
<STATE>TX
<ZIP>78701
</MAIL-ADDRESS>
</REPORTING-OWNER>
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>SILICON LABORATORIES INC
<CIK>0001038074
<ASSIGNED-SIC>3674
<IRS-NUMBER>742793174
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>400 W CESAR CHAVEZ
<CITY>AUSTIN
<STATE>TX
<ZIP>78701
<PHONE>5124168500
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>400 W CESAR CHAVEZ
<CITY>AUSTIN
<STATE>TX
<ZIP>78701
</MAIL-ADDRESS>
</ISSUER>
<DOCUMENT>
<TYPE>4/A
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2006-12-08</periodOfReport>

    <dateOfOriginalSubmission>2006-12-12</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001038074</issuerCik>
        <issuerName>SILICON LABORATORIES INC</issuerName>
        <issuerTradingSymbol>SLAB</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001338515</rptOwnerCik>
            <rptOwnerName>Sayiner Necip</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>400 W CESAR CHAVEZ</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>AUSTIN</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>78701</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President and CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, $0.0001 par value</value>
            </securityTitle>
            <transactionDate>
                <value>2006-12-08</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>33618</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.0001</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>174306</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">This Amended Form 4 is filed for the purpose of correcting the erroneously reported number of securities acquired as set forth in the Form 4 filed by the reporting person on December 12, 2006. The number of securities acquired is herein correctly reported as 33,618.  The subsequent Form 4 filed by the reporting person on December 13, 2006 has not been amended to update the ownership amount as a result of this amendment.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Necip Sayiner</signatureName>
        <signatureDate>2006-12-14</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
