Delete comment from: Ken Shirriff's blog
The reason for the chopper is long-term stability. If you build a simple DC-coupled op-amp circuit, it's going to drift very slowly over time, and the Amelco op-amps were to some extent temperature stabilized by having some degree of symmetry and having transistors biased by diodes which would change with temperature in the direction opposite the transistor. Stability would be fine for a minute-long run but if you want to be running a simulation for an hour or more, even a tiny bit of drift can cause instability. Therefore, the chopper. Now, if only we could find a way to keep the integrator stages from leaking, then we might have a future for analogue computation...
Sep 23, 2019, 9:41:45 AM
Posted to Reverse-engineering precision op amps from a 1969 analog computer