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Whether this phase margin acceptable?

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shanmei

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Whether this phase acceptable?

The amplifier's phase and gain plot:


1.png

When gain=0dB, the phase marge=72, which is stable for the unit gain bandwidth 22.7MHz.

However, the phase changes a lot within the unit gain bandwidth, like a sine waveform. In this case, is it acceptable for the phase not monotonically decreasing? Thanks.
 

is it acceptable for the phase not monotonically decreasing?
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Acceptable in which regard, for which application?

First point, you say it's an "amplifier's phase and gain plot". The reported phase margin is only relevant for stability if the amplifier is operated in a feedback configuration with unity feedback factor.

Secondly, the high unity gain bandwidth is probably of limited use because the gain is rather low over the two last decades. It's not the gain curve wanted for an operational amplifier. In step response, the low gain plateau will show as an excessive settling time.

Although the feedback loop would be stable, you pay a price for tuning the amplifier characteristic with lead-lag elements.
 
You are right that the flat region of the gain is not good for settling.
 

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