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I have seen some previous vague questions related to a similar case but not for this topology.

The following circuit (source: http://stompville.co.uk/?p=470) shows an alternative topology for an active high pass filter. I have seen it in some instrumentaion literature as well, as a way of how to add some offset to the filtered signal.

enter image description here

Regarding the RC networks present in this circuit, I do not understand how the one composed by C2 and Rg can actually work as a high pass filter, since the capacitor is connected to ground - shouldn't it work as a low pass filter instead, as high frequencies would go through it? I have tried to analyze the circuit in order to understand this behaviour but I fail to find any answer. Is my understanding incorrect?

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I do not understand how the one composed by C2 and Rg can actually work as a high pass filter, since the capacitor is connected to ground - shouldn't it work as a low pass filter instead, as high frequencies would go through it?

The gain of that op-amp stage at high frequencies is: -

$$1+\dfrac{R_f}{R_g}$$

enter image description here

And at DC, the gain is unity because capacitor C2 has infinite impedance: -

$$1+\dfrac{R_f}{\infty} = 1$$

So, the op-amp stage can act like a high-pass filter in that it can amplify AC signals to a greater degree than DC signals.

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