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Electronic Photoreceptor
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Electronic Photoreceptor Sensor in a solid condition that converts solar energy into electric energy normally generates a current at the output. The impact of photons of a given energy causes the transition of electrons from the valence band to conduction band. The photoreceptor is the basic component of any optical communications system, and one of the critical elements with respect to benefits. Types Inside the category of photoelectric detectors we can find a variety of devices, each one presenting specific characteristics Photoresistor The photoconductor or photoresistor is one that changes the electrical resistance due to exposure of radiant energy that reaches them. The resistance generated varies depending on the light striking at his surface. A high intensity of light incident on the surface will cause a lower resistance, by contrast with a lower intensity of light will cause higher resistance. It can be found in laser printers, which bridges the gap between the laser beam to the core of the drum coater. In addition, modulating the laser intensity can be controlled with great precision the tone of the image that will ultimately be printed. Photodiode Photodiode is a semiconductor sensitive to visible or infrared light depending on their manufacturing equipment. The diodes have a normal direction of current flow, which is called direct current polarization. Therefore, the diode electric current passes and almost not allowed on the reverse: this is the basis of the operation of a diode. On the other hand the photodiode actual current (which varies with changes of light) is circulating in opposite direction allowed by the junction of the diode. This will cause an increasing in the current flow when the diode is excited by light. An example of application of photodiode is the remote control of a television. The controller sends an infrared signal and the photodiode captures Phototransistor A phototransistor is a transistor sensitive to light, usually infrared. The phototransistor is more sensitive than the photodiode due to the gain of the transistor. The most notable difference in the structure of a phototransistor, the phototransistor is the capsule, which is transparent or fully transparent, and is sensitive to light. The phototransistor conducts more or less current from the collector when it affects more or less light on their joints. As the photodiode, the phototransistor has a very short response time, so responds to fast light changes. Unlike the photodiode, the phototransistor gives much greater power variations due to an amplification that the photodiode does not have. There are two versions of phototransistors: transmission and reflections. The transistors can be used in proximity sensors, punched cards, tape drives. See also *Photoreceptor cell *Photoresistor *Photodiode *Phototransistor simple:Photoreceptor cell 
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