Question

With the help of a circuit diagram, explain the V-I characteristics of a PN junction diode in forward biasing.

Hint:

In forward bias, once the threshold voltage is exceeded, the current through the diode increases rapidly. Below this voltage, the diode does not conduct significant current.

Answer 1

Step 1: V-I Characteristics of a PN Junction Diode.
The V-I characteristics of a PN junction diode describe the relationship between the voltage across the diode and the current flowing through it. The diode has two modes of operation: forward bias and reverse bias.
Step 2: Circuit Diagram for Forward Bias.
In forward bias, the positive terminal of the battery is connected to the p-type material (anode), and the negative terminal is connected to the n-type material (cathode). This reduces the potential barrier of the junction, allowing current to flow once the applied voltage exceeds a certain threshold (typically 0.7V for silicon diodes).
The circuit diagram for forward bias is: \[ \text{[Battery]} \quad \text{[PN Junction Diode]} \quad \text{[Resistor]} \] Step 3: V-I Characteristics in Forward Bias.
In the forward bias region:
- When the applied voltage is less than the threshold voltage, no significant current flows through the diode (except for a small leakage current).
- As the applied voltage increases and exceeds the threshold (typically 0.7V for silicon), the diode starts to conduct, and the current increases rapidly with voltage.
- The relationship between the current and voltage is non-linear in the forward bias region.
The V-I curve in forward bias shows an exponential increase in current with increasing voltage after the threshold voltage is reached. Step 4: Conclusion.
The V-I characteristic of a PN junction diode in forward bias shows that the current remains very small until the voltage exceeds the threshold voltage, beyond which it increases exponentially. This is typical of semiconductor diodes.