The OPL530, OPL530-OC, OPL531, OPL531-OC contain a monolithic integrated circuit which incorporates a photodiode, amplifier, voltage regulator, Schmitt trigger and an NPN output transistor on a single silicon chip. The OPL530 and OPL531 includes a 10 K pull-up resistor (RL) from output to VCC. The OPL530-OC and OPL531-OC have an open-collector output. These devices exhibit very stable performance over supply voltages ranging from 4.5 V to 16 V and a wide range of irradiance levels.