Question: Q. 5. Explain briefly with the help of necessary diagrams, the forward and the reverse biasing of a $p-n$ junction diode. Also draw their characteristic curves in the two cases.
U[Delhi III 2017]
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Solution:
Ans. Circuit diagrams of $p-n$ Junction under forward bias reverse bias
$$ 1 / 2+1 / 2 $$
Explanation of $p-n$ junction working for forward and reverse bias
Characteristic curves for the two cases
In forward bias, applied voltage does not support potential barrier. As a result, the depletion layer width decreases and barrier height is reduced. Due to the applied voltage, electrons from $n$ side cross the depletion region and reach $p$ side. Similarly holes from $p$ side cross the junction and reach the $n$ side. The motion of charge carriers, on either side, give rise to current. In reverse bias, applied voltage support potential barrier. As a result, barrier height is increased, depletion layer widens. This suppresses the flow of electrons from $n \rightarrow p$ and holes from $p \rightarrow n$, thereby decrease the diffusion current. The electric field direction of the junction is such that if electrons on $p$ side or holes on $n$ side in their random motion come close to the junction. They will be swept to its majority zone. This drift of carriers give rise to the current called reverse current.
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