Delete comment from: Ken Shirriff's blog
(Some) analog computer op amps had more robust bypassing than commercial op amps do. Without the robust bypassing, they can become unstable in circuits where the loop gain is <1. A VERY common phenomenon is in common audio compressors, that are known to produce chirp with high-volume inputs that force the gain below one. The usual "cure" for this is to attenuate the signal before a compression stage that limits its compression to be >=1. That this is SO unfamiliar to engineers is seen in commercial compressors - most of which have this high-signal chirp. Of course, analog computer setups would commonly have ops operating with less than unity gain, so this would NOT be good in an analog computer. Have you seen any additional components that appear to be addressing bypassing, possibly by limiting low-frequency gain to achieve a more gradual rolloff?
May 29, 2025, 2:14:36 PM
Posted to Reverse-engineering precision op amps from a 1969 analog computer