I used op-amp for my project and supplied with +12 and -12 volts. My PCB will have 4 layers which are TOP (signal layer), POWER (internal plane), GROUND (internal plane), BOTTOM (signal layer). When I split the power plane for supply voltages such as +12V, +5V , +3.3V . I'm confused where to set my -12V power for op-amp supply.
Should I set -12V to POWER plane or GROUND plane and why?