The OPL535, OPL535-OC, OPL536, OPL536-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 OPL535 and OPL536 include a 10 K pull-up resistor (RL) from output to VCC. The OPL535-OC and OPL536-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.