Nichols Plot: Gain and Phase Margins

The Nichols plot displays the frequencies at which the magnitude and phase cross 0 db and -180 respectively. If the gain or phase margin is infinite, Inf is displayed. It also tells you whether the system is stable or unstable.

Brown Stems

When the gain or phase margin is finite, a brown stem appears to represent the margin. The gain margin is the horizontal brown stem, and the phase margin the vertical one.

Hiding the Displays

To turn off the gain and phase margin displays, clear Stability Margins under Show in the open-loop Nichols plot right-click menu.