Phase Margin

Phase margin is a measure of system stability in control systems, indicating how close the system is to becoming unstable. It is the amount of additional phase shift, usually measured in degrees, needed at the system's gain crossover frequency (where the loop gain equals one) to make the system gain oscillate indefinitely. A larger phase margin means the system is more stable with better damping, while a smaller margin suggests it is closer to instability. Essentially, phase margin quantifies the buffer before feedback causes undesirable, sustained oscillations or system failure.