To plot Volt‒Ampere Characteristics of P-N Junction Diode

PN Junction diode characteristics (A) Forward bias (B) Reverse bias

Aim

1. To plot Volt‒Ampere Characteristics of P‒N Junction Diode.

Apparatus

Theory

A p‒n junction diode conducts only in one direction. The V‒I characteristics of the diode are curve between voltage across the diode and current through the diode. When external voltage is zero, circuit is open and the potential barrier does not allow the current to flow. Therefore, the circuit current is zero. When P‒type (Anode is connected to + ve terminal and n‒type (cathode) is connected to ‒ve thermal of the supply voltage, is known as forward bias. The potential barrier is reduced when diode is in the reduced when diode is in the forward biased condition. At some forward voltage, the potential barrier altogether eliminated and current starts flowing through the diode forward voltage.

When N‒type (cathode) is connected to + ve terminal and P‒type (Anode) is connected ‒ ve terminal of the supply voltage is known as reverse bias and the potential barrier across the junction increases. Therefore, the junction resistance becomes very high and a very small current (reverse saturation current) flows in the circuit. The diode is said to be in OFF state. The reverse bias current due to minority charge carriers.

Circuit diagram

(i) Forward bias

(ii) Reverse bias

V‒I Characteristics

Procedure

(i) Forward bias (For 'Ge' and 'Si' Diode)

1. Connections are made as per the circuit diagram.

2. For forward bias, the RPS +ve is connected to the anode of the diode and RPS ‒ ve is connected to the cathode of the diode,

3. Switch ON the power supply and increases the input voltage (supply voltage) in Steps.

4. Note down the corresponding current flowing through the diode and voltage across the diode for each and every step of the input voltage.

5. The readings of voltage and current are tabulated.

6. Graph is plotted between voltage on x‒axis and current on y‒axis.

Observations

Forward bias

Procedure

i) Reverse bias

1. Connections are made as per the circuit diagram.

2. For reverse bias, the RPS +ve is connected to the cathode of the diode and RPS ‒ve is connected to the anode of the diode.

3. Switch ON the power supply and increase the input voltage (supply voltage) in Steps.

4. Note down the corresponding current flowing through the diode and voltage across the diode for each and every step of the input voltage.

5. The readings of voltage and current are tabulated.

6. The Graph is plotted between voltage on x‒axis and current on y‒axis.

Observations

Reverse bias

Precautions

1. While doing the experiment do not exceed the rating of the diode. This may lead to damage the diode.

2. Connect voltmeter and Ammeter in correct polarities as shown in the circuit diagram.

3. Do not switch ON the power supply unless you have checked the circuit connections as per the circuit diagram.

Result

The Forward and Reverse bias characteristics for a p‒n diode are observed.