Bandgap: Phase Margin. Negative and positive loops

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jc2

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I want to measure the phase margin of a bandgap reference source, but I do not know how to do it. I measure the phase margin in the negative loop? or in the positive loop? or in the two loops at the same time???.

This source has two feedback loops, negative loop and positive loop. I know that the negative loop gain has to be higher than the positive loop gain at all frequencies. I also know that I have to do .tran simulations for checking oscillations in the output. But, I also have to simulate the phase margin at all the corners. My problem is that i do not know how to measure the phase margin, because the circuit has two loops.

This is the bandgap reference source.



Thanks in advance.
 

disconnect at the common mode of negative & positive loops, which would sum all the effects of the both.
 
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