Also contains definitions of: Darlington phototransistor, field effect phototransistor
A bipolar transistor with its base-collector junction acting as a @[email protected], which, if irradiated, controls the response of the device. Due to the inherent current gain (of the transistor) the responsivity of the phototransistor is greater than that of photodiodes. A Darlington phototransistor consists of two separate transistors coupled in the [email protected]@ Darlington configuration with a phototransistor as the input transistor. A field effect phototransistor or photo-FET is a @[email protected] transistor (FET) that employs photogeneration of carriers in the @[email protected] region (the neutral region sandwiched between the insulator and the depletion region under the gate of the FET). It is characterized by high responsivity due to the high current gain of the FET.