PHOTO DIODE

What is a Photo Diode?

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A Photo Diode is an photo detector capable of converting light into either current or voltage depending on the mode of operation. Photo Diodes are designed to opearte in reverse bias condition.
Photo diodes are semiconductor light sensors that can generate a current or voltage when the PN junction is illuminated by light.

When photon of sufficient energy has stricks the diode , then it exites an electron ,there by creating a free electron. This phenomenon is called as inner Photo Electric Effect. If the absorption occurs in the junctions depletion region or, one diffusion length away from it ,these carriers are swept from the junction by the built-in field of the depletion region .Thus holes move towards the cathode and electrons moves towards the anode and a Photo Current is produced. This Photo Current is sum of the dark current and light current , and dark current must be minimized to enhance the senstivity of the device.
Symbol of Photo Diode is Given By

Photo Diodes can be used in three ways .photo voltaic as a solar cell , Reverse- biased as a photo detector and a forward biased LED. Photo Diodes are similar to semiconductor diodes except that they may be exposed to Detect UV rays or X-rays. These Photo Diodes are made up of semi conductor materials like Silicon, Germanium, Indium.

FEATURES OF A PHOTO DIODE:

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Here are the Some of the features of a photo Diode.
1.Excellent Linearity with respect to incident Light.
2.Low Noise.
3.Wide Spectral Response.
4.Mechanically Rugged.
5.Compact and Light Weight.
6.Long Life.

APPLICATIONS:

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1. Photo Diodes are used in consumer electronics such as  CD players, smoke detectors and receivers. 
2. Photo Diodes are used  as light sensors.
3. Photo Diodes are often used for accurate measurement of light intensity in Light industry.
4. Photo Diodes are used in solar cell to generate Electric solar power . 

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And also see: KNOW ABOUT LIGHT EMITING DIODE