I've designed a very simple constant current source (just to learn more about them). While I was testing it on a breadboard by shorting it using a multimeter to measure the current everything was fine, so I designed a PCB and sent it out for manufacture. The PCB came back and I populated it.
When I tested it again with my multimeter everything was fine, but when I decided to test it with a simple red LED (which I didn't remember to test even when I had it on a breadboard) it didn't light up (with the current set to 20mA). So I decided to measure the current through it: 0uA and the voltage 1.245V.
I'm really intrigued by why the LED isn't lighting up and why there's no current through it. Could anyone explain to me why it doesn't work?
Here's my schematic, you can also check it in
my GitHub repo: