The 4N25 is an optocoupler, also known as an optoisolator, designed to transfer electrical signals between two isolated circuits using light. This family includes the N25, 4N26, 4N27, 4N28. Functional operation of the device is not implied at these or any other conditions in excess of those given in the operational sec. 4N25 belongs to one of the most famous families of optocouplers. It contains a light e itting diode optically coupled to a photo-transistor.
[PDF Version]