ActiveFilters：有源滤波器

《ActiveFilters：有源滤波器》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。

1、ENTC3320ActiveFiltersFiltersAfilterisasystemthatprocessesasignalinsomedesiredfashion.Acontinuous-timesignalorcontinuoussignalofx(t)isafunctionofthecontinuousvariablet.Acontinuous-timesignalisoftencalledananalogsignal.Adiscrete-timesignalordiscretesignalx(kT)is

2、definedonlyatdiscreteinstancest=kT,wherekisanintegerandTistheuniformspacingorperiodbetweensamplesTypesofFiltersTherearetwobroadcategoriesoffilters:Ananalogfilterprocessescontinuous-timesignalsAdigitalfilterprocessesdiscrete-timesignals.Theanalogordigitalfilter

3、scanbesubdividedintofourcategories:LowpassFiltersHighpassFiltersBandstopFiltersBandpassFiltersAnalogFilterResponsesH(f)ffc0H(f)ffc0Ideal“brickwall”filterPracticalfilterIdealFiltersPassbandStopbandStopbandPassbandPassbandPassbandStopbandLowpassFilterHighpassFil

4、terBandstopFilterPassbandStopbandStopbandBandpassFilterM(w)M(w)wwwwwcwcwc1wc1wc2wc2Thereareanumberofwaystobuildfiltersandofthesepassiveandactivefiltersarethemostcommonlyusedinvoiceanddatacommunications.PassivefiltersPassivefiltersuseresistors,capacitors,andind

5、uctors(RLCnetworks).Tominimizedistortioninthefiltercharacteristic,itisdesirabletouseinductorswithhighqualityfactors(rememberthemodelofapracticalinductorincludesaseriesresistance),howeverthesearedifficulttoimplementatfrequenciesbelow1kHz.Theyareparticularlynon-

6、ideal(lossy)TheyarebulkyandexpensiveActivefiltersovercomethesedrawbacksandarerealizedusingresistors,capacitors,andactivedevices(usuallyop-amps)whichcanallbeintegrated:Activefiltersreplaceinductorsusingop-ampbasedequivalentcircuits.OpAmpAdvantagesAdvantagesofac

7、tiveRCfiltersinclude:reducedsizeandweight,andthereforeparasiticsincreasedreliabilityandimprovedperformancesimplerdesignthanforpassivefiltersandcanrealizeawiderrangeoffunctionsaswellasprovidingvoltagegaininlargequantities,thecostofanICislessthanitspassivecounte

8、rpartOpAmpDisadvantagesActiveRCfiltersalsohavesomedisadvantages:limitedbandwidthofactivedeviceslimitsthehighestattainablepolefrequencyandthereforeapplicationsabove100kHz(passiveRLC