4N25, 4N26, 4N27, 4N28 Vishay Semiconductors Optocoupler, Phototransistor Output, with Base Connection DESCRIPTION The 4N25 family is an industry standard single channel phototransistor coupler. This family includes the 4N25, 4N26, 4N27, 4N28. Each optocoupler consists of gallium arsenide infrared LED and a silicon NPN phototransistor. FEATURES