What is photo diode

What does photodiode mean?

A photodiode is a device that helps in conversion of light electric current. It is a made of semiconductor material and containing a P-N junction and also it is designed to function in revere bias. Reverse bias means that the p - side of the photodiode is connected to the negative terminal of the battery and n - side means is connected to the positive terminal of the battery. It is also sometimes referred as a photodiode detector, photo sensor or light detector. Photodiode technology has been successfully and widely used due to its low-cost rugged structure.

A photodiode is very sensitive to light so when light or photons fall on the photodiode it easily converts light into electric current. A solar cell is also known as large area photodiode because it converts solar energy or light energy into electric energy. However solar cell works in bright light.

Photodiode symbol :

The schematic symbol of a photodiode is given below.  This diode is in order to convert the modulated electrical light back into an electrical signal type, Photodiode is one type of light detector.
Schematic symbol of a photodiode 
Photodiode looks like a light emitting diode. They have two terminal, one is a smaller end and other is a longer end. The longer end of the diode is the anode terminal while smaller end of the diode is cathode terminals. The characteristics of a photodiode are operated in a reverse bias mode.


The main feature of photodiode includes the  following ways :
  • Long life
  • Quick response
  • The linearity of the diode is too much good with respect to incident light 
  • Noise is very low
  • High Gain
  • Low cost
  • Long lifeline
  • Smaller size
  • Low sensitivity to temperature
  • High response speed
  • Small output current
  • Lightweight
  • Output change with respect to temperature change
  • Wide spectral responseApplied reverse voltage  be low
  • It will be always operated in reverse bias condition
Types of photodiode :

There are different types of photodiode such as :

There are many numerous types of photodiode available in the market.  They all work on the same basic principle, but working on different types of photodiode work in a slightly different way. A photodiode can be classified based on its construction are as follows given below :
  • PN photodiode - It is the first type of photodiode to be developed but not as widely used as others due to better performance parameters of other types of photodiodes.
  • PIN photodiode - It is one of the most widely used photodiodes, It generally offers lower capacitance and efficiently collects light photons better than PN photodiodes.
  • Avalanche photodiode -  It provides very high gain levels but comes with high noise levels
For detailed information :
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Application of Photodiode :
  • An optical fiber communication system
  • Automotive devices
  • Solar cell panels
  • Medical devices
  • Demodulation
  • Camera light meters
  • Street lights
  • Logic circuit
  • Photodetection circuits
  • Character recognition circuit
  • Televisions and remote control in VCRs
  • Measurement of the intensity of light in science and industry
More detailed information 

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