LMV342: oscillation issue

Hi David,

such a high resistance in the feedback path of a voltage follower is a no-go! Together with the inherent input capacitance of OPAmp is forms a low pass filter providing a phase lag which finally erodes the phase margin of OPAmp. This results in Instability and oscillation!

What exactly is U9A driving?

Kai

Hi Kai,

I got original schematic.

1. When VA is floating, ADC0_VA_REF is oscillated

2. When R6 is removed, ADC0_VA_REF is oscillated

Hi David,

what is connected to the output of U1B? A cap? The ref input of an ADC? Which ADC?

Kai

David,

What is the purpose of R7? Try adding 10pF (or higher) from pin 7 node to pin 6 node.