光电二极管的应用电路

ApplicationcircuitexamplesofSiphotodiode1.Lownoiselight-sensitivepreamplifierUsedinreceiversforspatiallighttransmissionandopticalremotecontrol.Areversebiasisappliedtothephotodiodetoimprovefrequencyresponse.ThiscircuitoutputsanamplifiedsignalfromtheFETdrain,butsignalscanalsobeextractedfromthesourcesideforinterfacetothenextstagecircuitwithlowinputresistance.KPDC0014ED2.Low-level-lightsensorheadThewholecircuitishousedinametallicshieldboxtoeliminateexternalEMI(electromagneticinterference).Thephotodiodewindowsizeshouldbeassmallaspossible.Useofanopticalfibertoguidethesignallightintotheshieldboxisalsoeffectiveincollectinglight.Ifdrybatteriesareusedandhousedinthesameshieldboxtosupplypowertotheoperationalamplifier,noiseoriginatingfromtheACsourcecanbeeliminatedandtheS/Nratiowillbefurtherimproved.KPDC0016ED3.LightbalancedetectioncircuitTheoutputvoltageVoofthiscircuitiszeroiftheamountoflightenteringthetwophotodiodesPD1andPD2isequal.Thephotoelectricsensitivityisdeterminedbythefeedbackresistance.ByplacingtwodiodesDinreverseparallelwitheachother,Vowillbelimitedtoabout±0.5V(maximum)inanunbalancedstate,sothattheregionaroundabalancedstatecanbedetectedwithhighsensitivity.Useofaquadrantphotodiodeallowstwo-dimensionalopticalaxisalignment.KPDC0017EB4.LuxmeterThisisanilluminometerusingavisual-compensatedphotodiodeS7686andanoperationalamplifier.Amaximumof5000lxcanbemeasuredwithavoltmeterhavinga5Vrange.Itisnecessarytouseanoperationalamplifierwhichcanoperatefromasinglevoltagesupplywithalowbiascurrent.Astandardlampshouldbeusedtocalibratetheilluminometer.Ifnostandardlampisavailable,anincandescentlampof100Wcanbeusedforapproximatecalibrations.Tomakecalibrations,firstselectthe1mV/lxrangeinthefigureattherightandshortthewiperterminalofthe500WvariableresistorVRandtheoutputterminaloftheoperationalamplifier.Adjustthedistancebetweenthephotodiodeandtheincandescentlampsothatthevoltmeterreads0.38V.Atthispoint,illuminanceontheS7686photodiodesurfaceisabout100lx.ThenopentheshortedterminalsandadjustVRsothatthevoltmeterreads1.0V.Calibrationhasnowbeencompleted.KPDC0018EC-+ISC2ISC1PD2PD1RfDD23764-15V+15VVoA10k10µ+15V1k0.1µFET0.1µRS1MRLPD0.1µ1000p10µVo++PD:High-speedPINphotodiodes(S5052,S2506-02,S5971,S5972,S5973,etc.)RL:DeterminedbysensitivityandtimeconstantofCtofphotodiodeRS:DeterminedbyoperationpointofFETFET:2SK152,2SK192A,2SK362,etc.PDVo236A1-+326+5V-5V0CfRf2Rf1S1S210-TURNPOTENTIOMETER10µ10µ++A2-+51METALICSHIELDEDBOXISCBoldlinesshouldbewithinguardedlayoutoronteflonterminals.A1:AD549,etc.Rf:10GWMax.A2:OP07,etc.S:Low-leakagereedrelayCf:10to100pF,polystyrenecapacitorPD:S1226/S1336/S2386series,etc.PD:S1226/S1336/S2386series,etc.A:LF356,etc.D:ISS270A,etc.Vo=Rf×(Isc2-Isc1)(V)(Vo±0.5V)Whentheamountoflightenteringthetwophotodiodesisequal,theoutputvoltageVowillbezero.Inunbalancedstate,Vowillbe±0.3to0.5V.Thiscircuitcanbeusedforlightbalancedetectionbetweentwospecificwavelengthsusingopticalfilters.IC:ICL7611,TLC271,etc.PD:S7686(3.8µA/100lx)*Metercalibrationpotentiometer100p1k1kPD10k100k1M200p006p(9V)VOLTMETER500VR*76843210.1(mV/lx)1(mV/lx)10(mV/lx)IC+-IscV15.Lightsensorusinghigh-speedoperationalamplifier(1)Thiscircuitusesahigh-speedphotodiodeappliedatareversevoltageandacurrent-to-voltageconversionoperationalamplifier.ThetimeresponseofthecircuitgreatlydependsonthetimeconstantofthefeedbackresistanceRfanditsparallelstraycapacitance.Tominimizetheeffectofthistimeconstant,twoormoreresistorsareconnectedinseriesasthefeedbackresistancetodispersetheparallelstraycapacitance.Useofchipresistorsasthefeedbackresistancewillbeeffectiveinreducingthestraycapacitance.KPDC0020EE6.Lightsensorusinghigh-speedoperationalamplifier(2)Thislightdetectioncircuitusesahigh-speed,current-feedbackoperationalamplifier,andallowsdirectconnectiontoacoaxialcable.Becausethiscircuitperformssignalamplificationaftercurrent-to-voltageconversionbyloadresistanceRL,therewillbenodetrimentaleffectswhichresultfromaphaseshiftintheamplifier.Aswiththecircuit5.,twoormoreresistorsareusedasthefeedbackresistancetodisperseparallelstraycapacitanceintheresistors.Aceramiccapacitorof0.1µFisconnectedtothepowersupplypinoftheIC,andshouldbegroundedataminimumdistance.Forbandwidthsover100MHz,useofchipresistorsandcapacitorsisrecommendedtoreducetheentirecircuitsizeandsuppresstheundesiredeffectsofleadinductanceofeachcomponent.PerformancecanalsobeimprovedbyusingagroundplanestructureinwhichtheentirecopperfoilsurfaceonthePCBisusedatthegroundpotential.KPDC0015ED7.Light-to-logarithmic-voltageconversioncircuitTheoutputvoltageofthiscircuitisproportionaltothelogarithmicchangeinthedetectedlightlevel.Abase-emitterjunctionofsmallsignaltransistorsoradiodebetweenthegate-sourceofjunctionFETscanbeusedasthelogdiodeD1.IBisthecurrentsourcethatsuppliesthelogdiodewithabiascurrent.IfIBisnotpresent,thecircuitwillbeunstableorlatchedupwhenIscbytheincidentlightdecreasestozero.KPDC0021EA8.High-speedlightdetectorusingPINphotodiodeThiscircuitusesnoactivecomponents.Sincenosignalamplificationisperformed,thiscircuitismainlyusedfordetectionatrelativelyhighlightl