The SFH628A-4 is a through-hole Phototransistor made by Vishay. It is an NPN silicon device with a circular package and a radial lead. The device is designed for use with infra-red light and provides high sensitivity, dark current, and fast switching speed. The phototransistor also has a wide optical wavelength response, ranging from 500-900 nm. In addition, it can operate across a wide temperature range of -55 to +100 degrees Celsius. The SFH628A-4 is designed to be used in applications such as sensing, light transmission, switching, and analog control.