Phototransistoren

A phototransistor is a semiconductor device that amplifies the current flowing through it when it is exposed to light. It is essentially a bipolar transistor where the base region is exposed to incident light. When photons strike the semiconductor material in the base-collector junction, they generate electron-hole pairs. These generated charge carriers act as the base current, which in turn controls a larger collector current. The sensitivity of a phototransistor to light can be adjusted by its physical construction and the materials used. They are typically more sensitive than photodiodes because of the inherent amplification within the transistor structure. Phototransistors are often packaged with a lens to focus light onto the sensitive area. They can be used in a variety of applications, including light sensors, optical switches, and as replacements for mechanical switches where electrical isolation is beneficial. Common uses include automatic lighting controls, infrared remote controls, and object detection systems. The output signal is an electrical current that varies proportionally to the incident light intensity.