Question

condidering a forward bias n-p junction and reverse bias n-p junction, which one produces a rectifying action? explain how it produces the rectifying action

Answer 1

Out of a forward bias n-p junction and a reverse bias n-p junction, a reverse bias n-p junction produces a rectifying action.

So basically, if the p-side of the junction is connected to the negative terminal and the n-side to the positive terminal of a battery, the junction is said to be reverse biased. In this case the potential barrier becomes higher as the battery further raises the potential of the n-side, see the figure below. In the figure the width of the depletion region is more for a reverse biased p-n junction, than the unbiased.

The width of the depletion region is increased. Diffusion becomes more difficult and hence the diffusion current decreases. The drift current is not appreciably affected and hence it exceeds the diffusion current. So there is a net current from the n-side to the p-side. However the drift current is small( in microamperes) so the net current is even smaller. Thus, during a reverse bias only a small current is allowed by the junction. Hence, we say that a reverse biased n-p junction provides a rectifying action.