Positive Negative dB Gain Margin dB Gain Margin 0 g Logo g L 180° 1809 270 go 270 Positive hase Margin Negative Phase Margin Stable System Unstable System 99 Log Log Log Log −90 −270 −180 Positive Gain Margin Positive Phase Margin Negative Gain Margin Negative Phase Margin Stable System Unstable System 0 dB −90 −270 −180 0 dB c x c x