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一种低频信号产生装置的设计方法.docx

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一种低频信号产生装置的设计方法 Introduction Lowfrequencysignalgeneratorsarecommonlyusedinvariousindustries,suchasaudioandradiofrequencyequipmenttesting,biomedicalresearch,andindustrialcontrolsystems.Thedesignofalowfrequencysignalgeneratorinvolvestheselectionofappropriatecomponentsandcircuittopologytoachievethedesiredperformance.ThispaperpresentsadesignmethodforalowfrequencysignalgeneratorthatutilizesaWienbridgeoscillatorcircuit. DesignMethod TheWienbridgeoscillatorisatypeofoscillatorthatcanproducealowfrequencysinusoidalwave.Itsfundamentalcircuitcomprisesofanamplifier,afeedbacknetworkconsistingoftwocapacitorsandtworesistors,andabridgenetworkconsistingoftworesistorsandacapacitor.Thecircuitisdesignedsuchthatthefrequencyofoscillationisdeterminedbythevaluesoftheresistorsandcapacitorsinthefeedbackandbridgenetworks. ThefirststepindesigningaWienbridgeoscillatorcircuitistoselecttheamplifier.Inthiscase,aunity-gainoperationalamplifier(OpAmp)isused.TheOpAmpprovidesthenecessarygaintosustaintheoscillationofthecircuit.ApopularchoiceistheLM741,whichisreadilyavailableandhasgoodperformancecharacteristics. Thenextstepistoselectthevaluesoftheresistorsandcapacitorsinthefeedbacknetwork.AccordingtotheWienbridgeoscillatortheory,thefrequencyofoscillationcanbeexpressedas: f=1/(2πRC) WhereRandCarethevaluesoftheresistorsandcapacitorsinthefeedbacknetwork,respectively.Toproducealowfrequencysinusoidalwave,thevaluesofthesecomponentsmustbecarefullyselectedtoensurethatthefrequencyofoscillationiswithinthedesiredrange. Assumingadesiredfrequencyof1kHz,thevaluesofRandCcanbecalculatedasfollows: R=1/(2πfC) C=1/(2πfR) Substitutingthevalues,weget: R=15.92kΩ C=10nF Thenextstepistodesignthebridgenetwork,whichconsistsoftworesistorsandacapacitor.Thepurposeofthebridgenetworkistoimprovethestabilityoftheoscillatorbyprovidingazeroimpedancepathtogroundatthefrequencyofoscillation. Thevaluesoftheresistorsinthebridgenetworkmustbecarefullyselectedtomatchthevaluesoftheresistorsinthefeedbacknetworktoachievemaximumgainandoscillation.Todo