4N35 Optocoupler IC (2 in pack)

4N35 is a popular and industry-standard optocoupler IC having a phototransistor output with base connection. It can provide up to 5kV electrical isolation between circuits, ensuring that high voltage signals and spikes from one circuit do not affect the lower voltage control circuitry.

Common applications include logic ground isolation, AC mains detection, reed relay driving, power supply regulation, protection from ground loops etc. Optocouplers are also referred to as photocouplers or opto-isolators.