The issue I am concerned about is the load capacitance seen by a MM phono cartridge driving a two stage feedback amplifier. In the case of a single stage with no FB Miller is pretty straightforward being proportional to the gain of the stage. If we add a second stage and bring FB from the second plate to the first stage cathode does the cartridge still see the same capacitance (approx. Cgp*A) or is it modified by the FB?
It is reduced by the feedback. (That also means that the + 1 term you neglected becomes a larger part of the total capacitance.)
Just look at the ratio of the AC voltage needed to drive the output stage and the input voltage of the first stage and add 1. Then multiply Cgp by that number. If the closed-loop gain drops with frequency, it could be that you mainly get a resistive effect rather than a capacitive effect:
Just look at the ratio of the AC voltage needed to drive the output stage and the input voltage of the first stage and add 1. Then multiply Cgp by that number. If the closed-loop gain drops with frequency, it could be that you mainly get a resistive effect rather than a capacitive effect:
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