LPF doubt

Nigel Goodwin said:

It doesn't go through the IC, the filter is R and C.

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MikeMl said:

No, the way this filter works is that a special signal is coupled into the right end of the top wire via the capacitor.

Think of it as an RC filter, except that instead of the bottom end of the C being grounded, the IC injects a signal into the shunt capacitor, which modifies the output function. This is five-pole filter; if it where just the series R and shunt C, then it would be only a single-pole filter...

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