主動濾波器介紹.ppt

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1、主動濾波器介紹學生:楊淞淵M9520112指導教授:梁治國教授濾波器簡介擷取感測元件輸出之類比訊號時，常需使用「濾波器(filter)」以擷取某特定頻率範圍之訊號，除去不必要之雜訊。濾波器可分為被動(passive)和主動(active)兩種。被動式濾波器包含有電阻、電感、電容等電子元件，功能僅在過濾雜訊主動式濾波器除電阻、電感、電容外，還包含有電晶體或運算放大器，可放大濾波後之訊號（即具有增益），且由於使用獨立電源，信號源與負載電路隔離性較佳濾波器的基本分類「低通濾波器(Lowpassfilter)」「高通濾波器(Highp

2、assfilter)」「帶通濾波器(Bandpassfilter)」「帶拒濾波器(Bandrejectfilter)」Lowpassfilter低通濾波器的功能是使低頻訊號通過，高頻訊號衰減，適用於高頻雜訊之過濾。Numericalanalysis(1/2)※Cutoffferquency※Q※InputimpedanceLowpassfilterNumericalanalysis(2/2)ZIN(min)=R1=27kCutoffFrequencyFilterQInputImpedanceLowpassfilterPract

3、icalDesignTechniques(1/3)※Cutoffferquency=1.5kHz※Q=0.707※Inputimpedance>10kΩLowpassfilterPracticalDesignTechniques(2/3)LetuschooseC1=3300pF，C2=6800pFComputetheRatioofC2/C1ComputeR1andR2LowpassfilterPracticalDesignTechniques(3/3)ComputeR1andR2R3=R1+R2=22kΩ+22kΩ=44kΩS

4、lewRate★SelecttheOPAmpLowpassfilterHighpassfilter高通濾波器是指高於截止頻率之訊號通過，低於截止頻率之訊號衰減的電路。Numericalanalysis(1/2)※Cutoffferquency※Q※InputimpedanceHighpassfilterNumericalanalysis(2/2)CutoffFrequencyFilterQInputImpedanceZIN(min)=R1=47kHighpassfilterPracticalDesignTechniques(1

5、/3)※Cutoffferquency=300Hz※Q=0.707※Inputimpedance>2kΩ※Highestinputferquency5000HzHighpassfilterPracticalDesignTechniques(2/3)LetuschooseR120kΩ，R2=10kΩDeterminetheR1/R2RatioComputetheValueofC1andC2LetuschooseC=0.033uFHighpassfilterPracticalDesignTechniques(3/3)Compute

6、theValueofR3R3=R1=20kΩSlewRate★SelecttheOPAmpHighpassfilterBandpassfilter帶通濾波器之用途是只使特定頻帶之訊號通過的電路。Numericalanalysis(1/3)※Resonantferquency※Q※Bandwidth※VoltagegainBandpassfilterNumericalanalysis(2/3)FilterQResonantferquencyBandpassfilterNumericalanalysis(3/3)Bandwidth

7、VoltagegainattheResonantferquencyBandpassfilterPracticalDesignTechniques(1/3)※Resonantferquency=8kHz※Q=0.707※VoltagegainatfR=unity※Bandwidth=800HzBandpassfilterPracticalDesignTechniques(2/3)LetuschooseC1=0.001uF，C2=0.001uFComputetheValueofR1ComputetheValueofR2Bandpa

8、ssfilterPracticalDesignTechniques(3/3)ComputetheValueofR3ComputetheValueofR4BandwidthSlewRate★SelecttheOPAmpBandpassfilterBandrejectfilter