I was playing around a little more today with my Analog Discovery 2 USB oscilloscope, and found that one could set up the power supplies to be high-power waveform generators by setting configuration 6 in the device manager. The power supplies are not great function generators, of course, as they are switching power supplies, but I can see some use cases for this functionality.
The power supplies are nominally limited to 700mA, so I wondered whether they had the same sort of sharp clipping that the function generator has (see FET I-vs-V with Analog Discovery 2). I tested the power waveform generator with several different loads:
We can get a clearer idea of the behavior by looking at the difference between the power waveform generator and the normal waveform generator:
With no load, the noise on the power waveforms is about ±4mV, but at high load, it drops to about ±1mV.
The noise is periodic with a frequency of about 1.024kHz, which is much too low a frequency for a switching regulator—it is actually from the sampling frequency for the waveform generator generating a 1Hz triangle wave (210 samples in wavetable). The usual waveform generator has four times as high a sampling frequency, so the error is mostly just quantization error from the power waveform generator, though a single step from the power waveform generator takes about 250µs to settle, so the 1Hz maximum frequency for the power waveform channels seems reasonable. With a 10Ω load, the settling time is reduced to about 50µs and the noise on each step is about 500µV RMS (not counting the quantization error).
With the 1.8Ω load, I let the current get as high as 927mA (well above the 700mA specification), and there is no sign of clipping. We can more reasonably model the power waveform generator as having an internal resistance. For the 1.8Ω and 10Ω loads, I plotted the equivalent internal resistance as a function of voltage (for the larger voltages):
I believe that the power waveforms will be useful for characterizing transistors, especially for sweeping a range of Vds voltages that require a substantial current.