A Phototransistor is a kind of transistor that is sensitive to light. It comprises of a photodiode & a transistor which is used to detect light and convert it into an electrical signal. The phototransistor was invented by John Northrup Shive in 1950 at Bell Telephone Laboratories. Its operation is based on the concept of the photoelectric effect. That is, when light is incident on a surface, t...read more