lm317 3-12 volt with optocoupler

[metalgarri]

I'm absolutely with FvM on this one. Adding gain to any feedback path, without proper loop analysis and stabilization, is a recipe for disaster.

The circuit can break into oscillation at any time.

As FvM suggested in a previeus post, a capacitor can be placed between the inverting in and the output of the opamp, in order to add a dominant pole to the loop and with some math the phase margin can be set at the wanted value.