buddypoor
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Hi newic,
just for my and your understanding:
When you start the simulation at very low frequencies (1mHz for example), you will notice that there is a difference at low frequencies between cases 1 and 3. Case 1 gives you not the loop gain (which must be negative) but the positive gain of the closed loop circuit. However, because the inv. input has a large C to ground, both are identical in magnitude for medium and higher frequencies. Nevertheless, case 1 does not comply with the phase margin definition, which applies only to the loop gain.
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