When I feed a 1V sine wave into both ch1 and ch2 of my Tek 2465A, and set it to display the difference (invert ch2 and add the channels), I do not see the expected flat line. Rather, there are some bumps.
So, I presume this means that one or both input amps are not quite linear.
My questions are:
- How much nonlinearity should I expect, in a working and well-tuned 2465A?
- Anybody got any pointers to where in the service manual I should look, for diagnostics and troubleshooting of this? (The service manual I have is a not-so-good photocopy so it's very hard to search through without at least a head start, and I haven't spent much time with it.)
- If I wanted to buy a used differential instrumentation amplifier, ideally with bandwidth >= 100MHz, ground-referred common mode range >= +/-15V, input-referred wideband noise = 20, is there a "classic" model that I should search for? (Sort of like the 2465 'scopes are a "classic" - something that would be easy to find used, easy to find a manual for, and that would be pretty reliable.)
Thanks!
-walter