<SEC-DOCUMENT>0001387467-13-000036.txt : 20130219
<SEC-HEADER>0001387467-13-000036.hdr.sgml : 20130219
<ACCEPTANCE-DATETIME>20130219194707
ACCESSION NUMBER:		0001387467-13-000036
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20130214
FILED AS OF DATE:		20130219
DATE AS OF CHANGE:		20130219

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Dotz Mary
		CENTRAL INDEX KEY:			0001314205

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-34717
		FILM NUMBER:		13624959

	MAIL ADDRESS:	
		STREET 1:		280 N BERNARDO AVENUE
		CITY:			MOUNTAIN VIEW
		STATE:			CA
		ZIP:			94043

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ALPHA & OMEGA SEMICONDUCTOR Ltd
		CENTRAL INDEX KEY:			0001387467
		STANDARD INDUSTRIAL CLASSIFICATION:	SEMICONDUCTORS & RELATED DEVICES [3674]
		IRS NUMBER:				000000000

	BUSINESS ADDRESS:	
		STREET 1:		475 OAKMEAD PARKWAY
		CITY:			SUNNYVALE
		STATE:			CA
		ZIP:			94085
		BUSINESS PHONE:		408-830-9742

	MAIL ADDRESS:	
		STREET 1:		475 OAKMEAD PARKWAY
		CITY:			SUNNYVALE
		STATE:			CA
		ZIP:			94085

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	ALPHA & OMEGA SEMICONDUCTOR LTD
		DATE OF NAME CHANGE:	20070123
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_136132121538663.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2013-02-14</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001387467</issuerCik>
        <issuerName>ALPHA &amp; OMEGA SEMICONDUCTOR Ltd</issuerName>
        <issuerTradingSymbol>AOSL</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001314205</rptOwnerCik>
            <rptOwnerName>Dotz Mary</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>475 OAKMEAD PKWY</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SUNNYVALE</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94085</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Chief Financial Officer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Shares</value>
            </securityTitle>
            <transactionDate>
                <value>2013-02-14</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>4533</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>9653</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Employee Share Option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>8.45</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2013-02-14</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>20400</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>2023-02-14</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Shares</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>20400.0</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>20400</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Represents the Issuer's common shares underlying restricted stock units (RSUs) awarded to the Reporting Person. The RSUs shall vest in equal annual installments over four (4) years from the grant date of February 14, 2013, provided the Reporting Person remains in the Issuer's service through each such date.</footnote>
        <footnote id="F2">Includes 8,311 shares subject to a restricted stock unit awards that will be issued as those units vest.</footnote>
        <footnote id="F3">The option will vest and become exercisable with respect to one-forth (1/4) of the underlying shares on the first anniversary of February 14, 2013, and thereafter the balance of the option shares will vest and become exercisable in a series of thirty-six (36) successive equal monthly installments, provided the Reporting Person remains in the Issuer's service through each such date.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Mary Dotz</signatureName>
        <signatureDate>2013-02-19</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
