CBSE Class 12-science Answered
Explain, with the help of a circuit diagram, the working to a photo-diode. Write briefly how it is used to detect the optical signals.
Or
Mention the important considerations required while fabricating a p-n junction diode to be used as a Light Emitting Diode (LED). What should be the order of band gap of an LED if it is required to emit light in the visible range?
Asked by Topperlearning User | 04 Jun, 2014, 01:23: PM
Expert Answer
Photodiode is a special type of photo-detector. The general principle is electronic excitation from the valence band to conduction band by photons. If an optical photon of frequency 
is incident on a semiconductor, such that its energy is greater than the band gap of the semiconductor, it will excite an electron from the valence band to the conduction band, leaving a vacancy or hole in the valence band. Thus, an electron-hole pair will be created. These are called 'photo generated charge carriers' which increases the conductivity of the semiconductor.
It can detect optical signals :
Working:
OR
Considerations:
Answered by | 04 Jun, 2014, 03:23: PM
Concept Videos
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Applications of p-n Diode - Part 1
This video explains the diode in a forward and a reverse bias. -
PN diode application
Diode V-I characteristics Diode as a rectifier Special purpose diodes. -
Applications of pn Diode
Diode V-I characteristics Diode as a rectifier Special purpose diodes
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