EE-301 Lab Manual, ME Department, Wah Engineering College
Lab Experiment # 06
Verification of characteristics curve of Zener Diode
Objective: To Verify the characteristics curve of Zener Diode.
Apparatus:-
1KΩ Resistor
Zener diode
Dc Power Supply
Ammeter
Voltmeter
Software Used:-
Proteus
Theory:-
A Zener diode is a diode which allows current to flow in the forward direction in the same
manner as an ideal diode, but also permits it to flow in the reverse direction when the voltage is
above a certain value known as the breakdown voltage, "zener knee voltage", "zener voltage",
"avalanche point", or "peak inverse voltage".
Figure-1
Operation:-
A conventional solid-state diode allows significant current if it is reverse-biased above 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 may be permanently damaged due to overheating. A zener diode
exhibits almost the same properties, except the device is specially designed so as to have a
reduced breakdown voltage, the so-called zener voltage. By contrast with the conventional
device, a reverse-biased zener diode exhibits a controlled breakdown and allows the current to
keep the voltage across the zener diode close to the zener breakdown voltage. For example, a
diode with a zener breakdown voltage of 3.2 V exhibits a voltage drop of very nearly 3.2 V
across a wide range of reverse currents. The zener diode is therefore ideal for applications such
as the generation of a reference voltage (e.g. for an amplifier stage), or as a voltage stabilizer for
low-current applications.
EE-301 Lab Manual, ME Department, Wah Engineering College
Figure- 2-1 Figure- 2-2
Construction:-
The zener diode's operation depends on the heavy doping of its p-n junction. The depletion
region formed in the diode is very thin (<1 µm) and the electric field is consequently very high
(about 500 kV/m) even for a small reverse bias voltage of about 5 V,
allowing electrons to tunnel from the valence band of the p-type material to the conduction band
of the n-type material.
Applications:-
Zener diodes are widely used as voltage references and as shunt regulators to regulate the
voltage across small circuits. When connected in parallel with a variable voltage source
so that it is reverse biased, a zener diode conducts when the voltage reaches the diode's
reverse breakdown voltage. From that point on, the relatively low impedance of the diode
keeps the voltage across the diode at that value.
Zener diodes are also used in surge protectors to limit transient voltage spikes.
Another notable application of the zener diode is the use of noise caused by its avalanche
breakdown in a random number generator.
Results:-
1. From Proteus:-
For Forward Bias:
Figure- 3-1 Circuit Diagram
EE-301 Lab Manual, ME Department, Wah Engineering College
Figure- 3-2 Current Output Figure- 3-3 Voltage Output
For Reverse Bias
Figure- 4-1 Circuit Diagram
Figure- 4-2 Current Output Figure- 4-3 Voltage Output
EE-301 Lab Manual, ME Department, Wah Engineering College
2. From Hardware:-
For Forward Bias
V s (V) V R (V) V D (V) I D (µA)
0 0 0 0
1 0.43 0.704 0
2 1.39 0.75 0
3 2.1 0.75 0
4 3.33 0.76 0
5 4.30 0.76 0.1
6 5.16 0.77 0.1
7 6.18 0.77 0.1
8 7.34 0.78 0.1
9 8.34 0.78 0.1
10 9.3 0.78 0.1
11 10.3 0.78 0.1
12 11.23 0.79 0.1
13 12.2 0.79 0.1
14 13.2 0.79 0.1
15 14.19 0.79 0.1
16 15.23 0.80 0.1
17 16.2 0.80 0.1
18 17.2 0.80 0.1
19 18.2 0.80 0.1
20 19.2 0.80 0.1
Table- 1
For Reverse Bias:
V s (V) V R (V) V D (V) I D (µA)
0 0 0
1 0 0
2 0 0
3 0.01 0
4 0.12 0.1
5 0.55 0.1
6 1.32 0.1
7 2.17 0.1
8 3.08 0.1
9 4.04 0.1
10 4.99 0.1
11 6 0.1
12 7.03 0.1
EE-301 Lab Manual, ME Department, Wah Engineering College
13 8.06 0.1
14 8.94 0.1
15 9.9 0.2
16 10.9 0.2
17 11.8 0.2
18 12.9 0.2
19 13.85 0.2
20 14.8 0.2
Table- 2
Conclusion:-
From the above experiment, it can be concluded that the value of V R , V D and I D increases with
the increase in source voltage both in forward bias and reverse bias condition.
