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1、摘 要收音机的发展一般经过电子管、晶体管再到集成电路。集成电路收音机由于使用元器件少、可靠性强、耗电省、成本低、重量轻、体积小等优点，已经开始取代分立元件式晶体管收音机。此接收机采用的就是单片调频调幅集成电路ULN2204。UNL2204集成电路有以下几个特点：其内部几乎包括了收音机所必需的电路，有独立的调幅振荡器、调幅双平衡混频器、调幅和调频中频放大器、调幅和调频解调器、AGC电路、AFC电路和功率放大器等。为使外接元件少且便于集成，ULN2204内部大量采用直接耦合的电路形成；工作电压范围宽。UNL2204内部设有精密稳压电路，而且外加电源电压的范围大，其允许变动的范围为3～12V
2、；用集成双差分放大电路组成混频器，提高了对信号中干扰成分的抑制能力；灵敏度高。具有5级中频放大，级间均采用直接耦合。前4级可以加AGC控制；外接元件少。中频放大直接耦合，无需外接元件。整个功率放大部分只接1只退耦电容；功率放大器的输入阻抗高，约为200千欧姆；调幅收音机与调频收音机的转换十分简单，仅用1只2*2波段开关，控制UNL2204内部的电子开关，完成调幅收音与调频收音的转换。此调频调幅接收机的电源供给采用自带直流稳压电源直接供给。关键词：调频 调幅 接收机 ULN2204 集成电路FM-AMReceiverAbstractThedevelopmentofgeneraloverth
3、eradiotubes,transistorstointegratedcircuits.ICRadioastheuseoffewercomponents,reliability,lowpowerconsumption,lowcost,lightweight,smallsize,etc.,hasbeguntoreplacediscretetransistorradio.Thisreceiverisusedinsingle-chipFM-AMICULN2204.UNL2204IChasthefollowingcharacteristics:itsinternalincludesalmostn
4、ecessaryfortheradiocircuit,independentamplitudemodulationoscillator,amplitudemodulationdouble-balancedmixer,IFamplifierAMandFM,AMandFMdemodulator,AGGcircuit,AFCcircuitandpoweramplifier.Toenablesmallandeasytointegrateexternalcomponents,ULN2204housealargenumberofdirect-coupledcircuitformation;wideo
5、peratingvoltagerange.UNL2204areequippedwithsophisticatedinternalregulatorcircuit,andtheexternalpowersupplyvoltagerange,whichallowschangesintherange3～12V;pairsofdifferentialamplifierwiththeintegratedcircuitmixersimprovethecomponentsofthesignalinterferencesuppressioncapabilities;sensitivityhigh.Wit
6、ha5-IFamplification,directcouplingbetweenstagesareused.4canbeaddedbeforetheAGCcontrol;fewerexternalcomponents.IFamplificationdirectcouplingdon’thaveaccessexternalcomponents.Thenthepoweramplifierpartofaretreatisonlydualcapacitor;poweramplifierinputimpedancehigh,about200thousandohms;AMradioandFMrad
7、ioconversionisverysimple,onlya2*2bandswitch,thecontrolelectronicswithintheUNL2204switch,thecompletionofAMradioandFMradioconversion.TheFM-AMreceiverwithbuilt-inpowersupplyDCpowersupplydirectlytothesupply.Keywords: FM AM
