I designed this little photodiode amp, and it works fine, but if the power supplies come up in the wrong sequence, it hangs up. I should have expected this. If +6 comes up before -6, the -3.3 rail goes to
+1.2, and probably the negative LDO hangs up. I call this "power supply pull-through" but maybe there's a better term.These are cool:
It's a 1 amp, 30 volt schottky diode that drops into an 0603 footprint. We'll replace a couple of bypass caps, on the +3.3 and -3.3 rails.