I need a logic gate to check if A or B or C is negative voltage (referenced to the ground). It does not matter if the output is positive or negative logic (as long as it is in positive voltages)
Does this circuit work?
Do you see other solutions or improvements?
One problem I see is that out goes negative if "True".
I thought about this one too:
easier to compensate the voltage drop of the diodes by tuning the resistances. and I can invert the logic easily.
What I finally did, it works well:
The comparator has built-in reference, just tune the voltage divider to match it. I didn't use hysteresis, the comparator has a built-in hysteresis too, but only few mV.