Describe the working of a PN junction diode in following conditiona. No Biasb. Forward Biasc. Reverse Bias

a. No Bias: In the absence of any external voltage (no bias), the PN junction diode is in equilibrium. The concentration gradient causes the free electrons from the N-type region to cross the junction and combine with holes in the P-type region. Similarly, holes in the P-type region cross the junction and combine with electrons in the N-type region. This movement of charge carriers forms a depletion region, which has a built-in or barrier potential that prevents further movement of electrons and holes.

b. Forward Bias: When the PN junction diode is forward biased, the positive terminal of the battery is connected to the P-type region and the negative terminal to the N-type region. This reduces the barrier potential of the depletion region. The external voltage pushes the electrons and holes towards the junction, allowing current to flow. The diode conducts current easily in this condition.

c. Reverse Bias: When the PN junction diode is reverse biased, the positive terminal of the battery is connected to the N-type region and the negative terminal to the P-type region. This increases the barrier potential of the depletion region, making it difficult for the charge carriers to cross the junction. Hence, the diode does not conduct current under this condition, except for a very small leakage current.