Bode Plot vs Nyquist Plot vs Nichols Chart for Minimum Phase Systems in MATLAB
How to plot Bode, Nyquist, and Nichols stability charts in MATLAB and measure Gain Margin and Phase Margin?
John Michell answered .
2026-07-24
Minimum phase systems have all poles and zeros in the left-half s-plane. In MATLAB, plot stability margins using bode(), nyquist(), and margin():
% Define open-loop transfer function G(s)
G = tf([10], [1 4 5 0]);
figure;
margin(G); % Plots Bode diagram with GM and PM markers
figure;
nyquist(G); % Plots Nyquist stability locus
% Calculate numerical margins
[GM, PM, wcg, wcp] = margin(G);
fprintf('Gain Margin: %.2f dB\n', 20*log10(GM));
fprintf('Phase Margin: %.2f deg\n', PM);