Description
The 4N25 is an optocoupler for general purpose applications. It contains a light emitting diode optically coupled to a photo-transistor. It is packaged in a 6-pin DIP package and available in wide-lead spacing option and lead bend SMD option. Response time, tr, is typically 3 µs and minimum CTR is 20% at input current of 10 mA.

Applications
1.  I/O interfaces for computers
2.  System appliances, measuring instruments
3.  Signal transmission between circuits of different potentials and impedances