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The difference between the infrared receiving tube PD and PT


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The difference between the infrared receiving tube PD and PT


       The photodiode is actually a photoresistor that is very sensitive to light changes. The die of the photodiode is a PN junction with photosensitive properties and has unidirectional conductivity, so the intensity of the light can be used to change the current in the circuit. A photodiode is a semiconductor device that converts an optical signal into an electrical signal. Its core part is also a PN junction. The structure is different from that of a normal diode. In order to facilitate the reception of incident light, the PN junction area is as large as possible, the electrode area is as small as possible, and the junction depth of the PN junction is very shallow, generally less than 1 micron.


       PT is called phototransistor

       The structure of the phototransistor is similar to that of a common triode. The difference is that the phototransistor must have a light-sensitive PN junction as the photosensitive surface. Typically, the collector junction is used as a light receiving junction. Therefore, the phototransistor is essentially a common triode corresponding to a photodiode connected between the base and the collector.


       The structure is different: the photodiode has a PN structure, the phototransistor has the characteristics of a triode, and is generally composed of NPN and PNP. The common surface of the market is the NPN type.

       The output current is different: the phototransistor has the function of amplification, while the photodiode does not.

      The difference in response time: Since the photodiode has only one node, the response time is much faster than that of the phototransistor.

       For more information about infrared receiver tubes, please visit Shenzhen Chengguangxing Optoelectronics official website ( to learn, or contact us by phone.

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