i tested the circuit and it worked well but now i want to have a bandpass filter after the pream (HPF with fc=30 followed by LPF with fc=1000) but without affecting the value of the reference voltage which the half of supply voltage!Without the output capacitor the output of the opamp averages half the supply voltage. .
The preamp has three coupling capacitors that create a very droopy passive highpass filter. They can be calculated for 30Hz but then 30Hz will be -9dB instead of -3dB. A Sallen and Key lowpass active filter can be added to the output of the preamp. If the output capacitor of the preamp is removed then the preamp's output can bias the input of the active lowpass filter at half the supply voltage.i tested the circuit and it worked well but now i want to have a bandpass filter after the pream (HPF with fc=30 followed by LPF with fc=1000) but without affecting the value of the reference voltage which the half of supply voltage!
in other word, i want my final output after the filters to averages half the supply voltage!
i don't mind using either passive or active filters!
i just tested the circuit on a simulator with sallen key LPF and it worked well (thank you )The preamp has three coupling capacitors that create a very droopy passive highpass filter. They can be calculated for 30Hz but then 30Hz will be -9dB instead of -3dB. A Sallen and Key lowpass active filter can be added to the output of the preamp. If the output capacitor of the preamp is removed then the preamp's output can bias the input of the active lowpass filter at half the supply voltage.
by Jake Hertz
by Duane Benson
by Jake Hertz
by Jake Hertz