<SEC-DOCUMENT>0001387467-21-000030.txt : 20210317
<SEC-HEADER>0001387467-21-000030.hdr.sgml : 20210317
<ACCEPTANCE-DATETIME>20210317161259
ACCESSION NUMBER:		0001387467-21-000030
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20210225
FILED AS OF DATE:		20210317
DATE AS OF CHANGE:		20210317

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Chang Stephen Chunping
		CENTRAL INDEX KEY:			0001722000

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-34717
		FILM NUMBER:		21750686

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

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			ALPHA & OMEGA SEMICONDUCTOR Ltd
		CENTRAL INDEX KEY:			0001387467
		STANDARD INDUSTRIAL CLASSIFICATION:	SEMICONDUCTORS & RELATED DEVICES [3674]
		IRS NUMBER:				000000000
		FISCAL YEAR END:			0630

	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_161601195994725.xml
<DESCRIPTION>FORM 4
<TEXT>
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    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2021-02-25</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001722000</rptOwnerCik>
            <rptOwnerName>Chang Stephen Chunping</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>President</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Share</value>
            </securityTitle>
            <transactionDate>
                <value>2021-03-15</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
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            <transactionAmounts>
                <transactionShares>
                    <value>17500</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
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                <sharesOwnedFollowingTransaction>
                    <value>261662</value>
                    <footnoteId id="F2"/>
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                <directOrIndirectOwnership>
                    <value>D</value>
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        <nonDerivativeTransaction>
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                <transactionCode>F</transactionCode>
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                <transactionAcquiredDisposedCode>
                    <value>D</value>
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                <sharesOwnedFollowingTransaction>
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            <securityTitle>
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                <transactionCode>F</transactionCode>
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                    <footnoteId id="F5"/>
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                <transactionAcquiredDisposedCode>
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                <sharesOwnedFollowingTransaction>
                    <value>255660</value>
                    <footnoteId id="F2"/>
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            <ownershipNature>
                <directOrIndirectOwnership>
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        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Share</value>
            </securityTitle>
            <transactionDate>
                <value>2021-03-15</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
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                <transactionShares>
                    <value>1687</value>
                    <footnoteId id="F6"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>257347</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
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            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
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        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Share</value>
            </securityTitle>
            <transactionDate>
                <value>2021-03-15</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
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                <transactionShares>
                    <value>3750</value>
                    <footnoteId id="F7"/>
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                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
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                <sharesOwnedFollowingTransaction>
                    <value>261097</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
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            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Share</value>
            </securityTitle>
            <transactionDate>
                <value>2021-02-25</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
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            <transactionAmounts>
                <transactionShares>
                    <value>12000</value>
                    <footnoteId id="F8"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
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                <sharesOwnedFollowingTransaction>
                    <value>273097</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
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                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">The RSU shall vest in equal annual installments over four (4) years from March 15, 2021, provided that the Reporting Person remains in the Issuer's service through each such vesting date.</footnote>
        <footnote id="F2">Reflects 695 shares acquired under the Issuer's Employee Stock Purchase Plan on May 14, 2020 and 675 shares acquired under the Issuer's Employee Stock Purchase Plan on November 14, 2020.</footnote>
        <footnote id="F3">Includes an aggregate of 33,250 shares subject to Restricted Share Unit awards (RSU) granted on March 15, 2018, March 15, 2019, March 16, 2020, and March 15, 2021 which will be issued as such units vest in accordance with their terms, and excludes (a) 17,500 unvested common shares subject to the PSU granted on March 15, 2021, which may become vested upon achievement of certain corporate performance goals in the future and (b) 3,750 unvested common shares subject to the 2018 PSU which may be vested upon satisfaction of service-based vesting conditions by the Reporting Person.</footnote>
        <footnote id="F4">Shares withheld to satisfy the Issuer's tax withholding obligation upon the vesting of RSU granted on March 15, 2017, March 15, 2018, March 15, 2019, and March 16, 2020.</footnote>
        <footnote id="F5">Shares withheld to satisfy the Issuer's tax withholding obligation upon the vesting of Performance Share Units (PSU) granted on March 15, 2017, March 15, 2018, and March 16, 2020.</footnote>
        <footnote id="F6">Represents the issuance of common shares upon vesting of one-fourth (1/4) of performance share units (&quot;PSU&quot;) granted on March 15, 2017.  The achievement of specified performance goals for such PSU was certified previously by the Compensation Committee on March 15, 2018, and the issuance common shares thereunder are subject to additional service-based vesting conditions in four equal annual installment commencing in March 2018.</footnote>
        <footnote id="F7">Represents the issuance of common shares upon vesting of one-fourth (1/4) of PSU granted on March 15, 2018.  The achievement of specified performance goals for such PSU was certified previously by the Compensation Committee on February 27, 2019, and the issuance common shares thereunder are subject to additional service-based vesting conditions in four equal annual installment commencing in March 2019.</footnote>
        <footnote id="F8">Represents the vesting of PSU granted on March 16, 2020 upon the achievement of specified performance goals as certified previously by the Compensation Committee on February 25, 2021 and the issuance common shares thereunder are subject to additional service-based vesting conditions in four equal annual installment commencing in March 2021.</footnote>
        <footnote id="F9">Includes 9,000 unvested common shares subject to the 2020 PSU granted on March 16, 2020 which may be vested upon satisfaction of service-based vesting conditions by the Reporting Person.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Yanbing Hong, attorney-in-fact for Stephen Chang</signatureName>
        <signatureDate>2021-03-17</signatureDate>
    </ownerSignature>
</ownershipDocument>
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</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
