To verify the V-I characteristic of Zener diode





Objective

To verify the V-I characteristic of Zener diode and to determine Zener breakdown voltage.

Equipment Required

1. Zener diode
2. Voltmeter (0-2 volt)
3. Voltmeter (0-30 volt)
4. Mili-ammeter
5. Micro-ammeter
6. Variable source (0-2 volt and 0-30 volt).

Theory

A Zener diode is a type of diode that permits current not only in the forward direction like a normal diode, but also in the reverse direction if the voltage is larger than the voltage known as "Zener knee voltage" or "Zener voltage". The device was named after Clarence Zener, who discovered this electrical property. Zener diodes differ from ordinary diodes in that it special reverses bias characteristics .After a particular reverse voltage the diodes breakdown. In this region the voltage remain constant through the current veries.This characteristics of zener diodes helps in many circuits as regulators power supplies etc

Symbol of Zener Diode

A conventional solid-state diode will not allow significant current if it is reverse-biased below its reverse breakdown voltage. When the reverse bias breakdown voltage is exceeded, a conventional diode is subject to high current due to avalanche breakdown. Unless this current is limited by circuitry, the diode will be permanently damaged. In case of large forward bias (current in the direction of the arrow), the diode exhibits a voltage drop due to its junction built-in voltage and internal resistance. The amount of the voltage drop depends on the semiconductor material and the doping concentrations.

The Zener diodes operation depends on the heavy doping of its p-n junction allowing electrons to tunnel from the valence band of the p-type material to the conduction band of the n-type material.

Circuit Diagrams

Circuit diagram of zener diode

Procedure

1. Make connections as in circuit image given below.

2. Very the input by setting of potentiometer & measure the voltage across zener diode Vz.

3. Measure the current Iz for each setting of potentiometer form the ammeter.

4. Plot the graph between Vz & Iz

Observation

Observation table of zener diode

Result

V-I characteristics of zener diode

V-I characteristics of zener diode are determined. By the graph analysis we found that after Vz, current Iz, across the zener diode is constant.

Precautions

1) All the connection should be tight.

2) Ammeter is always connected in series in the circuit while voltmeter is parallel to the conductor.

3) The electrical current should not flow the circuit for long time, Otherwise its temperature will increase and the result will be affected

4) It should be care that the values of the components of the circuit is does not exceed to their ratings (maximum value).

5) Before the circuit connection it should be check out working condition of all the Component.

6) Circuit should be handling carefully.

Viva Questions and Answers for Diode action as a Clipper

Question.1: What is zener diode?

Question.2: Who discovered the zener diode?

Question.3: What is the basic principle of zener diode?

Question.4: Explain doping in Zener diode?

Question.5: What are the applications of zener diode?

Question.6: What is voltage-current (V-I) characteristics of zener diode?

Question.7: Explain the working of zener diode as voltage regulator?

Question.8: What are the limitations of shunt regulator?

Question.9: How can do Testing of Zener diode?

Question.10: What is the difference between zener diode & simple diode?



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