= Phase margin
{title2=$\mathrm{PM}=\pi+\arg L(\omega_c),\quad |L(\omega_c)|=1$}
The <phase margin> measures the remaining phase lag before a negative-feedback loop reaches the critical phase $-\pi$ at unity loop magnitude, using a continuous phase convention. Positive adequate margin is a useful stability and transient-response design diagnostic for standard single-crossover amplifier loops. More general unstable open-loop systems and multiple crossovers require the full stability criterion.
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