DIODE CHARECTERISTICS

DIODE CHARECTERISTICS

AIM

To plot the characteristics of a pn diode and to find its the cut in voltage and the dynamic resistance.

COMPONENTS AND EQUIPMENTS REQUIRED

1. DC supply

2. Diodes

3. Voltmeter

4. Ammeter

5. Rheostat

CIRCUIT DIAGRAM

THEORY

A diode is the basic electronic component. It’s property is that it can conduct only in one direction. A diode can be made by joining a p type semiconductor and an n type semiconductor. At the junction point there will be a voltage drop due to the migration of carriers. The voltage at this barrier is known as barrier potential. Ideally the barrier potential is zero. But in practical case there will be a drop of 0.7 Volts.

When the P side of diode is connected to the positive of power supply and N region is connected to the negative of supply, the diode is said to be in forward biased condition. At this condition, if the applied voltage is greater than the barrier potential of the diode, it starts conduction. After the diode is arrived in the conduction mode, the drop across it remains at 0.7 V. After the conduction starts, if the voltage is increased further, current trough it increases linearly with voltage.

When the supply voltage is reversed the diode is said to be in reverse biased condition. Here there is no conduction at lower voltage values .If we increase the voltage value further ,it is observed that at a voltage the current sharply increases due to the breakdown of the P-N junction. This damages the device. So care is to be taken while connecting diode in a circuit. The main applications of diode are:

1. As rectifier

2. As clippers

3. In clamping circuits.

PROCEDURE

1. Connect the circuit as given in the circuit diagram

2. Adjust the rheostat to make the voltage across diode is 0 Volts

3. Now vary the rheostat to increase the voltage across diode in steps of 0.1 volts and observe the corresponding current values.

4. Now take the readings of voltage and current values until voltage remains stationary.

5. Plot the graph

6. Now find the dynamic resistance from graph by taking the ratio of change in voltage to change in current. Static resistance at any point can be calculated directly by dividing the voltage by current at that voltage.

7. Now find the cut in voltage from the graph by taking the starting point of conduction.

OBSERVATION COLUMN

V(voltage)	I(current)

GRAPH

Cut in voltage=……………

Dynamic forward resistance at 10 mA=…………

Static forward resistance=……………………

RESULT

Characteristics of a P-N diode was plotted .Cut in voltage=………………..static resistance=…………………..dynamic resistance=………………..

SAMPLE VIVA QUESTIONS

1. What is barrier potential?

The voltage developed at the junction of a PN diode

2. What is cut in voltage?

The minimum forward voltage required to make the diode on

3. What are the applications of diodes?

a) Rectifiers

b) Clippers

c) Clampers

4. Mention the name of a diode.

1N4001

5. What is the 1N means?

Unijunction