The 4N45/46 optocouplers contain a GaAsP light emitting diode optically coupled to a high gain photodetector IC. The excellent performance over temperature results from the inclusion of an integrated emitter-base bypass resistor which shunts photodiode and first stage leakage currents as well as bleeding off excess base drive to ground. External access to the second stage base provides the capability for better noise rejection than a conventional photodarlington detector. An external resistor or capacitor at the base can be added to make a gain-bandwidth or input current threshold adjustment. The base lead can also be used for feedback. The high current transfer ratio at very low input currents permits circuit designs in which adequate margin can be allowed for the effects of optical coupling variations. The 4N45 has a 250% minimum CTR at 1.0 mA input current and a 7 V minimum breakdown voltage rating.
High current transfer ratio – 1500% typical
Low input current requirement – 0.5 mA
Performance guaranteed over 0°C to 70°C temperature range