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PT (Photo Transistor) is called photosensitive triode

The structure of photosensitive triode is similar to that of ordinary triode. The difference is that the photosensitive triode must have a light sensitive PN junction as the photosensitive surface, and the collector junction is generally used as the light receiving junction. Therefore, the photosensitive diode is essentially a common diode equivalent to a photosensitive diode connected between the base and the collector

PD (Photodiode) is called photodiode

Photodiode, in fact, is a photoresistor, which is very sensitive to changes in light. The core of the photodiode is a PN junction with photosensitive characteristics, which has single conductivity. Therefore, the current in the circuit can be changed by light intensity. Photodiode is a semiconductor device that converts optical signals into electrical signals. Its core part is also a PN junction. Compared with ordinary diodes, its structure is different. In order to accept the incident light, the PN junction area should be as large as possible, and the electrode area should be as small as possible. In addition, the junction depth of the PN junction is very shallow, generally less than 1 μ m.

The structure is different: the photodiode has a PN structure, and the photosensitive triode has the characteristics of a triode, which is generally composed of NPN and PNP. The most common type on the market is NPN

The output current is distinguished by: the phototransistor has the amplification function, while the photodiode does not Difference in response time: photodiodes have only nodes, so the response time is much faster than that of photodiodes