Please feel free to discuss the blog post linked below related to characterizing opamps.
Interesting project Matt, will this be a next “QAxxx” system? Could be something for testing op amps when your busy with some audio projects.
Maybe, once the other products get updated and/or the shortage has resolved. I think the board is a bit specialized for what most need these days, especially considering how good data sheets are. But what would be helpful (for me) is the ability to specify a list of tests, and then compare two opamps side by side on the exact same tester.
The output impedance contribution really matters at these distortion levels, and the ability to understand a lower bound for a load is important, because the tradeoff is noise. So, it’s a constant balance between distortion and noise.
Interesting project, thanks for sharing.
The citations were also illuminating… we may build this tester rig to use with both our QA and our new AP555 systems, it looks quite functional!
Hi @DanClark, the reality agrees well with the theory from the paper. In the plot below, you can see the opamp configuration 5A has a bit of crossover present (LM358) in inverting gain (20 dB) config. It’s hard to see the distortion in the time domain, but the residual display shows it clearly. In configuration 5B, the distortion is magnified to the point it’s readily visible in the time domain.