fototransistörden

A fototransistör, also known as a phototransistor, is a semiconductor device that combines a bipolar transistor and a photodiode. It is sensitive to light and its base current is controlled by the intensity of incident light. When light strikes the phototransistor's base-collector junction, it generates electron-hole pairs. These charge carriers are then amplified by the transistor's current gain, resulting in a larger collector current.

Phototransistors are essentially bipolar transistors with their base terminal exposed to light. The light acts as a trigger, allowing a small amount of light to control a larger current flow between the collector and emitter. They are typically used in applications where light needs to control an electrical circuit. Common uses include light-activated switches, optical encoders, infrared remote controls, and light-sensing applications.

Compared to photodiodes, phototransistors offer higher sensitivity due to their inherent amplification. However, they generally have a slower response time. The collector current of a phototransistor is roughly proportional to the light intensity, though this relationship is not perfectly linear. The spectral response of a phototransistor depends on the semiconductor material used. Silicon is common for visible light, while other materials are used for infrared detection. The package of a phototransistor is designed to allow light to reach the sensitive junction, often featuring a transparent lens or window.