Hi, I am trying to evaluate the phase margin over different output voltages for an audio power amplifier as in the demo located in C:\Program Files\QSPICE\Examples\MiddleBrook.qsch however the PHASEMARGIN vs Vout steps plot does not agree with the phasemargin measured on the loopgain vs frequency plots.
Here are screenshots of the demo simulation. The LoopGain vs frequency plot shows a phasemargin of about 73 degrees while the PHASEMARGIN vs Vout steps shows a phasemargin of about 63 degrees at the same Vout. Not sure if this is someting wrong with the .meas statement or if I am doing something wrong. I also noticed that the phasemargin values given by the .meas statement seem to be the Phase value at 5MHz not at the gain crossover frequency FT.
Any help with this is appreciated,
Thanks.
