一阶巴特沃斯低通滤波器电路图.doc

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1、一阶巴特沃斯低通滤波器电路图图1.一阶巴特沃斯低通滤波器电路图图1是一由运放741或351组成的一阶有源巴特沃斯低通滤波器电路图。截止频率fc=1/{2π(RC),增益Gp=1+(RF/R1).ThecircuitshowninFigure1isafirst-orderButterworthlow-passfilter.Alow-passfilterisacircuitthatblockssignalswithfrequenciesgreaterthanacut-offfrequencyfc.ThecircuitinFigure1usesanop-ampconf

2、iguredasanon-invertingamplifier,withanRCcircuitatthenon-invertinginputtodothefilteringofthehigh-frequencysignals.Thecut-offfrequencyfcofthiscircuitisdeterminedbyRandC,i.e.,fc=1/{2π(RC)}.Thepass-bandgainGpofthisfilterisgivenby:Gp=1+(RF/R1).Thus,ifthefrequencyfoftheinputsignalislowerth

3、anfc,Vo≈GpxVin.Iff=fc,Vo≈0.707GpxVin.Iff>fc,Vo

4、ade.Ifonedesiresabetterlow-passfrequencyresponsethanthis,thesecond-orderButterworthlow-passfilterinFigure2canbeused.Thiscircuitexhibitsa-40dB/decaderoll-offatf>fc,whereinfc=1/{2πxsqrt(R2R3C2C3)}.Also,forthiscircuit,magnitudeofVo/Vin=(1+RF/R1)/(sqrt(1+(f/fc)4)).