I am trying to build a Audio amplifier for a university project, I think that most of my circuit is done but I have an issue with my filter as my sine signal is not symmetrical after filtering to eliminate the offset, Instead of having an interval of aprox. +-5V I get an interval of +5 -> -7. I have used 3 opamps for amplifying the signal and a potentiometer at the first one so that I can increase my interval to 8V(maximum that I need to output).
As my input data I have:
- Ai = 700µV
Bandpass freq = 32 -> 512 Hz
Ao = 5-8 V
- Rl = 40 Ohm
Below is the circuit and simulation(transient of 10ms w/ step of 10u) I've tried using Chebyshev filter or a Active Butterworth Filter using some online calculators but I am getting from the computations two resistors with negative values and that's not ok.
I've tried using a active band pass filter but that also didn't work out; I can provide the project if needed.