this is true practicle no 9

1. V-I characteristic of zender diode
AIM :-
APPRATUS & MATERILALS :-
1. Regulated power supply
2. Milliammeter
3. Voltmeter
4. Multimeter
5. Bread board
6. Connecting wire
COMPONENTS :-
1. Zender diode 12V, a W or other suitable, 1 NO.
2. Carbon resistor, 720 Ω, 1 W NO.
THEORY
When PN junction diode is reverse biased, negligibly small
Reverse current flows. When the reverse voltage is increased beyond a
certain limit, there is sharp increase in the reverse current and the
voltage across the diode remains constant. This occurs. Zender diode
is designed to operate in the break down region without damage. By
adding the impurity in certain definite proportion, the breakdown
voltage can be accurately decided.
Zender diode is always operated in the reverse biased condition. When
reverse voltage is applied, very small reverse current flows. With
increase in reverse voltage, there is no noticeable rise in the reverse
current. At break over voltage current starts increasing with very small
change in the voltage across it.
Knee current or break over current is the minimum current at which
the zender diode starts functioning. It is denoted by Izk

2. Dynamic resistance of zender diode is defined as the ratio of small
change in the reverse voltage to the corresponding change in reverse
current. It is denoted by rd.
Rd
Since change In current is more compared to the change in voltage, the
dynamic resistance is less.
CIRCUIT DIAGRAM:-
PROCEDURE :-
1. From the data sheet note down the important specifications of
the diode used.
2. Connect the circuit as shown in the circuit diagram
3. Keep the output control knob of the regulated power supply at
the minimum position and switch on the supply.
4. Increase the input voltage from zero to maximum permissible
value in step and at every time measure the current Iz through
the zender diode, input d.c. voltage Vi and the voltage Vz across
diode.
5. Switch off the supply.
6. Draw the graph of voltage Vz and current Iz. this graph will be in
the third quadrant as both these quantities are negative.
7. Calculate the dynamic resistance from the characteristic.