Question

With reference to a semi-conductor diode, what is meant by
(i) Forward bias
(ii) Reverse bias
(iii) Depletion region.

Answer 1

Diode is an unipolar device, i.e. it has a p-type side and a n-type side, and their connection matters.

1. Forward Bias: When the p-type side of the diode is connected to a higher potential than the n-type side, the diode is said to be forward biased, because it enhances the capability of the diode to conduct forward current.

2. Reverse Bias: When the case is opposite and n-type side is kept at a higher potential than the p-type side, only a small amount of reverse saturation current flows through the diode, referring this condition as reversed biased.

3. Depletion Region: When p-n junction is formed, some of the free electrons in the n-region diffuse across the junction and combine with holes to form negative ions. In so doing they leave behind positive ions at the donor impurity sites.