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Questions about active band pass filter

Question asked by heyheydog on Apr 20, 2016
Latest reply on Apr 20, 2016 by heyheydog

     I would like to a band pass filter,so I designed with Filter Solutions and made a circuit.This is the circuit.6kHz center frequency and SALLENKEY topology,gain = 1

6kHz.png

     When I simulate this circuit in the Multisim,every thing is OK.When I test the real circuit board,I found the magnitude is so small,like 1/30 of the correct value.For example,if the input signal is 6000Hz 1Vpp,the output is 30mVpp.

     I tried a lot to find the problem.I ruled out the possibility that opamp made this,because the same phenomenon happened when I change several OP AMPs.When I change the R1 to a relative small value like several kilo ohms rather than dozens killo ohms,the problem solved.I am saying,in the Filter Solutions,keep the center frequency constant and change the capacitors with big values,then the R1 can be reduced to smaller one.

     So my question is,why this circuit's overall output magnitude relies on R1 and so different from simulation,is it due to parastic parameters or nonideal amplifier.

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