Phase Margin Rule of Thumb Phase Margin Block Diagram In order to prevent spam, users must register before they can edit or create articles.

1 Phase Margin Rule of Thumb

The phase margin is one of the robustness measures of a closed loop system under control. A low phase margin will lead to undesirable oscillations in the step response.

The phase margin can be determined from a:

• Bode Plot of the open loop transfer function magnitude crosses 0 dB
• Nichols Plot where the open loop transfer function magnitude crosses 0 dB

1.1 Minimum Recommended Phase Margin

A good rule of thumb for the phase margin is

Table 1: Minimum Phase Margin Recommendations

Application	Minimum Phase Margin (deg)
Tracking	40

Please feel free to add the recommended minimum phase margin for the applications you are familiar with.