I have found this circuit:
To me, this just looks like a two-pole passive filter going into a non inverting amplifier, the only difference is that that one capacitor is connected to the output. What exactly is the point of connecting the capacitor that way, does that somehow create resonance? And how does changing the resistance of the "Q control" resistor alter the resonance?
Also, this is a two-pole filter. If I wanted a four-pole filter, would I be able to just add two more RC circuits in front of the input? If so, would either of the two additional capacitors need to be connected to the output?
To me, this just looks like a two-pole passive filter going into a non inverting amplifier, the only difference is that that one capacitor is connected to the output. What exactly is the point of connecting the capacitor that way, does that somehow create resonance? And how does changing the resistance of the "Q control" resistor alter the resonance?
Also, this is a two-pole filter. If I wanted a four-pole filter, would I be able to just add two more RC circuits in front of the input? If so, would either of the two additional capacitors need to be connected to the output?