ZENER DIODE CHARECTERISTICS(lab manual)

ZENER DIODE CHARECTERISTICS

AIM

 To plot the reverse characteristics of zener diode and to find the breakdown voltage

COMPONENTS AND EQUIPMENTS NEEDED

1. 6.2 V zener diode

2. Resistors

3. Variable dc power supply

4. Voltmeter

5. Ammeter

CIRCUIT DIAGRAM

THEORY

        

         Zener diode is a P-N junction diode specially designed to operate in the reverse biased mode. It is acting as normal diode while forward biasing. It has a particular voltage known as break down voltage, at which the diode break downs while reverse biased. In the case of normal diodes the diode damages at the break down voltage. But zener diode is specially designed to operate in the reverse breakdown region.

         The basic principle of zener diode is the zener breakdown. When a diode is heavily doped, it’s depletion region will be narrow. When a high reverse voltage is applied across the junction, there will be very strong electric field at the junction. And the electron hole pair generation takes place. Thus heavy current flows. This is known as Zener break down.

       So a zener diode, in a forward biased condition acts as a normal diode. In reverse biased mode, after the break down of junction current through diode increases sharply. But the voltage across it remains constant

PROCEDURE

1. Test the components

2. Make the circuit as shown in the circuit diagram

3. Apply the voltage to the circuit in small steps

4. Note down the ammeter and voltmeter readings.

5. Note the voltage and current values carefully, after break down

6. Plot the graph and make the necessary calculations

OBSERVATIONS

V(VOLTS)	I(mA)

GRAPH

Now from graph

Resistance at 10 mA=…………..

Dynamic resistance=change in voltage\change in current=……..

Break down voltage=……………….

RESULT

Characteristics of zener diode were plotted.

Breakdown voltage=…………….

Dynamic resistance=…………….

SAMPLE VIVA QUESTIONS
 

1. What is the basic principle of zener diode?

        Zener breaks down 

2. What is zener break down?

        When a diode is heavily doped, it’s depletion region will be narrow. When a high reverse voltage is applied across the junction, there will be very strong electric field at the junction. And the electron hole pair generation takes place. Thus heavy current flows. This is known as Zener break down.

3. Mention any application of zener diodes

        In voltage regulators