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I have a 4 pole active LPF.

I am seeing that the amplitude of Vs1 & Vs2 is higher than the amplitude of input signal.

I am not sure how.

In my calculation, I have taken the amplitude of the fundamental harmonic of the square wave (input) into consideration, reduce it by 6db and multiply by the gain. The amplitude results don't quite match up with what I see in simulation (JPEG of the circuit and waveform attached).

Also, I am assuming that the output of the 1st stage (Vs1) is a triangular wave, so that I am considering the fundamental harmonic of a triangular for the calculation of amplitude of the 2nd stage (Vs2).

The other thing that I don't understand is how come Vs1 and Vs2 are shifted up by some DC value. Does capacitor charging/discharging has got something to do with it?

Thanks.

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# Sallen Key LPF Question

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