I have a circuit with about 24 op amps in it, they are all powered by +-15V rails. In the same circuit I have a bank of analog multiplexers and transistors acting as switches, they are running off +-5V.
The +-5V was being supplied by a 7805 and 7905, with input/output caps. Unfortunately they were causing the ground to rise about a millivolt, which was upsetting the virtual ground on my op amps. After protecting against backflow with diodes and reverse polarity etc. I was still having the same problem. I decided to try two zener diodes and I got the same issue!
This issue is occurring with or without the load connected, so it is not to do with the load. If I disconnect these power sources ground returns to zero. I assume it probably has something to to with uneven distribution of ground (it's on a breadboard). But even when I connected grounds accross with more wires it happens. My last guess is that there's oscillations, even with stabilising caps. Does anyone have any ideas?
TLDR: Power sources causing local ground to rise.
Cheers, Himmel
The +-5V was being supplied by a 7805 and 7905, with input/output caps. Unfortunately they were causing the ground to rise about a millivolt, which was upsetting the virtual ground on my op amps. After protecting against backflow with diodes and reverse polarity etc. I was still having the same problem. I decided to try two zener diodes and I got the same issue!
This issue is occurring with or without the load connected, so it is not to do with the load. If I disconnect these power sources ground returns to zero. I assume it probably has something to to with uneven distribution of ground (it's on a breadboard). But even when I connected grounds accross with more wires it happens. My last guess is that there's oscillations, even with stabilising caps. Does anyone have any ideas?
TLDR: Power sources causing local ground to rise.
Cheers, Himmel