gain and phase cross over frequency

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shopi Ram

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hai

For a system "with feedback" I have both gain and phase crossover frequency.

My question for this given system to be stable which one ( gain cross over frquency or phase cross over frequency) should be greater?

Also Pls explain me why that should be greater?

Thanks

Shobi
 

Hi Shobi,

you didn`t mention but I assume you speak about the loop gain response (that means: open loop!), right?
In this case, the gain cross-over frequency (loop gain 0 dB) should be lesss than the phase cross-over frequency (-180 deg or -360 deg, respectively).
In this case, the gain will be below unity (0 dB) when the phase reaches the critical limit and the closed-loop circuit will be stable.
 

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