Photodiode

 

·         Photodiode :



Photodiode Construction:

 

Photodiode: construction

            The construction of photo junction diode is similar to the p-n junction diode.

            But photodiode is placed in a transparent package so that light can reach p-n junction.

            The width of the depletion region W is large enough in photodiode, such that most of the photon are absorbed within W rather than n-region or p-region.

            W is made large by widely doping any one of the p or n region.

            Fig. shows a depletion layer photodiode.



 p-i-n photodiode :


Another method of constructing a photodiode is to build p-i-n photodetector.

The “i” region is intrinsic material sandwiched between p and n junctions.

When p-i-n photodetector is reverse biased the applied voltage appears entirely across the i region and there is vast change of current when photons are incident on it in the form of light.

In general, InGaAs, InP are the materials used to construct photodiode.

 

Operating Principle:


    Fig.- Photodiode circuit to study its operation

A photodiode is used in reverse bias mode.

When light strikes on p-n junction, a photon can dislodge valence electrons.

Hence, the amount of light striking the junction can control the reverse current in a diode which is called as photodiode.


Specification Parameters

The maximum reverse bias voltage, current and sensitivity, speed are the important parameters.

The response of photodiode to particular wavelength classifies the photodetectors as

 (i) invisible range of light and

(ii) infra-red region light response which is invisible


I-V Characteristics:



Applications:

            Photodiode is used in optocoupler where a LED and photodiode are enclosed in a single package and current through photodiode is controlled by light emitted by diode.

               Used in optical communication like remote controls, character recognition systems, burglar alarms etc.


for more details do visit my YouTube Channel "Easy Electronics"

Link for photodiode:-  https://youtu.be/2LZg7TtQ9uY

Location: India

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