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प्रश्न
With the help of a neat circuit diagram, explain the working of a photodiode.
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उत्तर
a. A photodiode is a special purpose P-N junction diode fabricated with a transparent window to allow light to fall on the diode.
b. When the photodiode is illuminated with light (photons) with energy h greater than the energy gap Eg of the semiconductor, then electron-hole pairs are generated due to the absorption of photons.
c. The diode is fabricated such that the generation of electron-hole pairs takes place in or near the depletion region of the diode.
d. Due to electric field of the junction, electrons and holes are separated before they recombine.
e. The direction of the electric field is such that electrons reach N-side and holes reach Pside. Electrons are collected on N-side and holes are collected on P-side giving rise to an e.m.f.
f. When an external load is connected, current flows. The magnitude of the photocurrent depends on the intensity of incident light.
g. It is easier to observe the change in the current with change in the light intensity, if a reverse bias is applied. Thus, photodiode can be used as a photodetector to detect optical signals.
संबंधित प्रश्न
Explain with the help of a diagram, how depletion region and potential barrier are formed in a junction diode.
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Even though the current in the forward bias is known to be more than in the reverse bias, yet the photodiode works in reverse bias. What is the reason?
Using the necessary circuit diagrams, show how the V-I characteristics of a p-n junction are obtained in
Reverse biasing
How are these characteristics made use of in rectification?
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Draw solar cells of I-V characteristics.
