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1、Source:ELECTRONICSTECHNOLOGYHANDBOOK1PASSIVEELECTRONICCOMPONENTSCONTENTSATAGLANCEOverviewFiltersFixedResistorsPassiveFiltersVariableResistorsPowerSupplyFiltersCapacitorsSurfaceAcousticWave(SAW)FiltersInductorsCrystalFrequencyStandardsTransformersOvervie
2、wApassiveelectroniccomponentisacircuitpartthatfunctionswithoutanexternalpowerrequirement.Themostcommonpassivecomponentsareresistors,capacitors,andinductors.Mostofthemhavetwoleads.Anaxial-leadedcomponent,asshowninFig.1-1,hasleadsprojectingfromeachendofth
3、ecomponentbodyalignedwiththelongaxisofthepart,whilearadial-leadedcomponent,asshowninFig.1-2,hasparallelleadsprojectingatrightanglesfromitsbody.Axialleadsmustfirstbebent90°toinsertthemintotheholesofcircuitboards,whileradialleadscantypicallybeinserteddire
4、ctlyintothoseholeswithoutbending.However,bothaxial-andradial-leadedpartscanbeinsertedbyautomaticmachines.1DownloadedfromDigitalEngineeringLibrary@McGraw-Hill(www.digitalengineeringlibrary.com)Copyright©2004TheMcGraw-HillCompanies.Allrightsreserved.Anyus
5、eissubjecttotheTermsofUseasgivenatthewebsite.PASSIVEELECTRONICCOMPONENTS2PASSIVEELECTRONICCOMPONENTS(a)Figure1-1Axial-leadedcomponents:(a)resistor,(b)and(b)electrolyticcapacitor.Figure1-2Radial-leadedcapacitors:(a)monolithicceramic,(b)solidtanta-lum,(c)
6、aluminumelectrolytic,and(a)(b)(c)(d)(d)ceramicdisk.Theongoingtrendtowardmoresurfacemountingofelectroniccomponentshasledtotheintroductionofmoreactiveandpassive“leadless”componentsthatcanbesoldereddirectlytotinnedorplatedpadson“hole-less”orsurface-mountte
7、chnology(SMT)circuitboards.PassiveSMTcomponentssuchascapacitorsandresistorsareleadlessrectangularchipsorcylinderswithmetallizedendsurfacesthatarereflowsolderedtothecircuitboards,butmanyactivecomponents,suchastransistorsandintegratedcircuits,areincaseswi
8、thbentstubor“gullwing”leadsthatcanalsobereflowsoldereddirectlytocircuitboardpads.FixedResistorsAresistorisacircuitcomponentthatprovidesafixedvalueofresistanceinohmstoopposetheflowofelectricalcurrent.Resistorscanlimittheamountofcu
