BPW77NA - 

BPW77NA and BPW77NB Series Phototransistors
The BPW77NA and BPW77NB series, from Vishay Semiconductor, are a range of silicon NPN phototransistors. They are in hermetically sealed TO-18 packages with a glass lens. The BPW77NA and BPW77NB phototransistors are sensitive to both visible and near IR radiation. They are ideal for use as detectors within electronic control and drive circuits.