Hi all, I have a beginner question, I try to make a very simple bandgap reference. And it does work. However, when I switched the connection of the gate of the FET to the other side. It just go crazy, can anyone explain what's going on? First picture is schematic with crazy behaviour, second one is schematic with good behaviour.

The one with the good behavior is having a positive feedback factor less than one, whereas the other one has a feedback factor greater than one