Anti-theft alarm accessory principle
Anti-theft alarm accessory principle
The phototransistor is also called a phototransistor, and its current is controlled by external light. It is a semiconductor optoelectronic device. It is much more sensitive than a photodiode, and the light concentrates on the area near the junction.
A semiconductor photodiode (APD) with internal gain can be obtained by using the avalanche multiplication effect, and another general-purpose transistor amplification principle can be used to obtain another photodetector having an intra-current gain, that is, a phototransistor. Its ordinary bipolar transistors are very similar, and are composed of two very close pn junctions - the emitter junction and the current collecting structure, and both have a current generating effect. In order to fully absorb photons, the phototransistor requires a large receiving surface, so its response frequency is much lower than that of the photodiode.
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