The Vishay optocoupler has a GaAs infrared emitting diode emitter, which is optically coupled to a silicon planar phototransistor detector, and is incorporated in a 4-pin 50 mil lead pitch mini-flat package. The coupling devices are designed for signal transmission between two electrically separated circuits.

High CTR with low input current
Low profile package (half pitch)
Low coupling capacitance
High common mode transient immunity