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When gain margin is infinite in Bode plot?
Recall that the gain and phase margins are measured on the Bode diagrams of the feedback loop gain, not on the transfer function of the overall system. When the phase of the loop gain never goes below -180 degree, then the gain margin is infinite.
What is phase margin in Bode plot?
The phase margin refers to the amount of phase, which can be increased or decreased without making the system unstable. It is usually expressed as a phase in degrees. We can usually read the phase margin directly from the Bode plot (as shown in the diagram above).
What is the ideal phase margin?
In general, the phase margin of 30–60 degrees and the gain margin of 2–10 dB are desirable in the closed-loop system design. A system with a large gain margin and phase margin is stable but has a sluggish response, while the one with a small gain margin and phase margin has a less sluggish response but is oscillatory.
What happens if gain margin is infinite?
A gain margin of infinty means that no matter how much you increase the gain, the system will always be stable. which has a pole at −kb, which is always negative because k and b are positive. So, no matter how large we take k, the system will always be stable and so the gain margin is infinite.
Can there be no gain margin?
All Answers (14) Increasing gain infinitely will increase oscillations in the system, which is not desirable. As the system admits a second order transfer function, there is no phase crossover frequency, and therefore the gain margin is infinite.
How do you increase phase margin?
You can increase the phase margin by making a dominant pole nearer to the zero frequency origin. This is accomplished by compensating the op amp through adding a shunting capacitor in the highest impedance node of the amplifier. This is a very well known technique which is used commonly to increase the phase margin.
Is infinite gain margin bad?
Can a system be stable with negative gain margin?
Gain margins are defined at 1/|G(jw)| with w=/180, with G beeing your frequency response. So now if |G(w=-180)| is bigger than 1, you will have a value in dB which is smaller 0dB. This does not tell you about the stability of the system. That said, you can have negative margins and a stable system, like in your case.