Accurate Loop Gain Measurements, Tips & Tricks

by Florian Hämmerle - OMICRON Lab
Loop Gain measurements are a powerful tool when designing a compensator of a switching power supply or to verify the small-signal stability of voltage regulators or switchers having a feedback circuit for a stabilized output voltage.

Since the availability of price effective vector network analyzers like the Bode 100, loop gain measurements have gained in popularity enabling the systematic stabilization and control design for simple as well as complex topologies in power electronic circuits.

In this presentation, the basics of the loop gain measurement method using voltage injection are reviewed and common pitfalls, like noise at low frequency, are explained in detail. Choosing the right measurement signal size is not only crucial to fight noise but also to get accurate results. The presentation includes tips and tricks for better measurements and demonstrates some of the most common challenges in a real-life demonstration.