Cadence gain and phase margin
The STB main form in Virtuoso will produce eval errors for any negative or gain phase margin, the same is true if you use the PhaseMargin function in the calculator. In cases such as these, doing it manually is sometimes the easiest way to see what is going on. Don't forget that ideally you want a phase margin of ~60, and general rule of thumb is &gt; 45 to ensure stability.