Question

Draw the circuit diagram of a p-n junction diode in
(i) forward biasing and
(ii) reverse biasing.
Also, draw its I-V characteristics in the two cases.

Hint:

In forward bias, current flows easily after the threshold voltage. In reverse bias, only a small leakage current exists until breakdown.

Answer 1

p-n Junction Diode Biasing Explained

A p-n junction diode permits current flow in one direction (forward bias) and obstructs it in the opposite direction (reverse bias).

(i) Forward Biasing:

• The p-side (anode) connects to the battery's positive terminal, and the n-side (cathode) connects to the negative terminal.
• This connection narrows the depletion region, enabling current passage.

Circuit Diagram for Forward Biasing:

I-V Characteristics in Forward Bias:

• Current escalates exponentially post the threshold voltage (0.7V for silicon, 0.3V for germanium).

(ii) Reverse Biasing:

• The p-side connects to the negative terminal, and the n-side connects to the positive terminal.
• This action widens the depletion region, inhibiting current flow, save for a minor leakage current.

Circuit Diagram for Reverse Biasing:

I-V Characteristics in Reverse Bias:

• A minimal leakage current persists until the breakdown voltage is attained.