Hi jpa I am watching your app with interest.
I am a DCDC converter designer and I am very interested to see if this app could be modified slightly to enable closed loop frequency response analysis of a power supply unit.
The idea is to inject a signal into the feedback loop of the power supply and see how the power supply responds at different frequencies therefore envestigating whether the power supply is likely to go unstable and if it is capable of responding to quickly changing load conditions. The output is a bode plot pretty much the same a you have generated except you would need to plot gains above 0dB
I think also as a precaution I would need to buffer the output signal through a high bandwidth amplifier before connecting it into my circuits to prevent overdriving the DSO Quads internal drive
So what do you think? Are you familiar with the technique and would it be easy enough to add some kind of range adjustment on the dB scale to allow for this?