Hello, I'm having an issue regarding the use of an LMV324 opamp in a untiy gain configuration. Normally, I use LM324 opamps with a negative supply near the part voltage limits and keep my signals far, far away from the rails, however in this design I only have a 0-5V supply and many of my signals are rail to rail as the opamp is advertized as. It seems that when I have a signal below 400mV for a significant period of time, the output of the opamp becomes unstable and unpredictable with non-period output swings anywhere between the rails. At worst, I was hoping the signals would clip at the rail, so this seems a little odd. I thought this might be some CM issue but I don't think I understand what is getting me here. Here is the ckt, basic, but I must be missing something. The 2.5V ref, is stable, but the load is between 1k and 100k and does not seem to have a correlation to when the output start to drift around, however I have not forced different loads on the output to see if one load causes more issues than others. I've used this configuration in a few places on the ckt, with better results (as far as I know), however I haven't investigated everything yet (doing that now 16 DUT and a long list of todos...), so I'm worried this might become a plaguing issue. Any design guidance on how to make this ckt more stable would be great! Will send a oscope capture once the ckt start to misbehave again. I've got some thoughts, but looking for someone with a bit more wisdom in this area.
