Opamp buffer with 400nF output capacitance going unstable?

[asdf44]

I also don't see the BJT helping. It's a follower topology so the output becomes [opamp out] - Vbe. It doesn't reduce the loop gain in any helpful way but insteads add more delay/poles.

I don't see how adding in a BJT is easier than a couple passives.

 

[FvM]

are trying to wangle what we have

What do you have? What's the meaning of post #18 in this regard, the BJT buffer has been newly introduced to this thread, apparently it's not on your PCB.

The existing PCB can be e.g. used with mentioned LM7321 as drop-in replacement. It's also expectable that LMC6221 and many other general purpose OPs are stable under certain capacitive load conditions, unfortunately the behavior can't be predicted based on datasheet information.

 

[treez]

What do you have? What's the meaning of post #18 in this regard, the BJT buffer has been newly introduced to this thread, apparently it's not on your PCB.

Thanks, what we actually have on the pcb is the schem in #18 [but the 2k7 (R5) is actually a 100n capacitor]

...we are currently wangling it to be as the schem in #17 (by not fitting the bjt and using a zero ohm between some of its pads, and not fitting the two 100n caps on the output)