PRACTICAL FOUR
BEHAVIOURAL ANALYSIS OF A DIODE
4.1 Aim of Experiment
The Aims of this experiment are
i. To study the reverse and forward characteristics of P-N junction diode.
ii. To study the reverse and forward current of diode.
iii. To study the characteristic of Zener diode.
iv. Learn circuit readings and tracing.
v. Appreciate the realization of circuit diagram (Fig 1.0) into a system. (Training
kit 004)
4.2 Requirements
i. Variable power supply.
ii. Two multi meters
iii. Connecting wires.
iv. Experiment KIT 004
4.3 Circuit diagrams
4.3.1 Circuit diagram (Fig 1.0)
4.3.2 circuit diagram of KIT 004
4.3.3 Circuit diagram for Zener diode
4.4 Set up and operation procedure
4.4.1 Procedures 1
i. The kit was traced on a piece of paper to determine its connection in relation to the
given circuit diagram. (Fig 1.0).
ii. Firstly, the power supply was adjusted to 10Volts and then connect the Kit to work
as circuit in fig 1.0 by select the forward connected silicon diode in KIT004.
iii. The reading of the forward current If was ____________________ (mA).
iv. The power supply was switched off and leave the voltage setting intact to 10 Volts.
v. The reverse connected silicon diode was selected in the KIT004.
vi. Then the power supply was switched on and reading of the reverse current was
taken IR was__________________ (mA).
vii. The value of Reverse to forward current was compared.
viii. Then the procedure (i) to (vii) was repeated using germanium diode.
4.4.2 Procedures 2
i. The kit was traced on a paper and its connection was determined
ii. The kit was connected according to the provided circuit
iii. A silicon diode was selected by using a jumper then germanium diode
iv. The voltage was set to 0 volts, then the power supply was adjusted till when
the voltmeter read 0.1v, 0.2v, 0.3v up to 2volts
v. A graph was plotted to show how the forward current varies with the voltage
vi. A comment was given on the observations made
4.4.3 Procedures 3
i. The power supply Voltage was adjusted when the Jumper was out so that the
Voltmeter read 0.5V then increased by step of 0.5V to 4.0V.Then the step
Voltage was reduced to 0.1 from 4.1 to 8Volts
ii. The value of current was read on the Ammeter (in mA) of each Voltage
setting
iii. Observe and note when the diode starts conducting
iv. Plot the V-I characteristic graph of the diode
v. Determine the zener breaking voltage of the diode (the voltage of which
voltage remains constant)
4.5 Results/findings;
4.5.1 TABLE OF RESULTS FOR FORWARD AND REVERSE CURRENT
AND VOLTAGE FOR SILICON AND GERMANIUM DIODES
Diode Silicon Germanium
Forward Voltage (V) 0.841 0.669
Forward Current (mA) 21.51 21.91
Reverse Voltage (V) 10.02 10.08
Reverse Current (mA) 0.00 0.00
4.5.2 TABLE OF RESULTS FOR FORWARD CURRENT AND VOLTAGE
FOR SILICON AND GERMANIUM DIODES
Voltage with Voltage with Current Reading
jumper jumper in(V) (mA)
out(V)
0.1 0.122 0.00
0.2 0.206 0.00
0.3 0.299 0.00
0.4 0.407 0.01
0.5 0.469 0.09
0.6 0.509 0.21
0.7 0.536 0.39
0.8 0.558 0.57
0.9 0.573 0.80
1.0 0.585 0.99
1.1 0.595 1.20
1.2 0.603 1.39
1.3 0.612 1.62
1.4 0.620 1.85
1.5 0.627 2.09
1.6 0.632 2.28
1.7 0.637 2.47
1.8 0.642 2.68
1.9 0.648 2.93
2.0 0.652 3.14
4.5.3 TABLE OF FORWARD CURRENT AND VOLTAGE FOR ZENER DIODE
Voltage with Voltage with Diodes
jumper and Jumper in Current
(V) (V) (mA)
0.0 0.000 0.00
0.5 0.052 0.00
1.0 1.04 0.00
1.5 1.53 0.00
2.0 2.00 0.00
2.5 2.51 0.00
3.0 3.05 0.00
3.5 3.52 0.00
4.0 4.01 0.00
4.1 4.10 0.00
4.2 4.17 0.00
4.3 4.27 0.00
4.4 4.39 0.00
4.5 4.52 0.00
4.6 4.60 0.00
4.7 4.72 0.00
4.8 4.81 0.00
4.9 4.87 0.00
5.0 4.99 0.00
5.1 5.10 0.00
5.2 5.20 0.00
5.3 5.28 0.00
5.4 5.41 0.00
5.5 5.52 0.00
5.6 5.63 0.00
5.7 5.71 0.00
5.8 5.79 0.00
5.9 5.94 0.00
6.0 6.01 0.00
6.1 6.07 0.00
6.2 6.19 0.00
6.3 6.31 0.00
6.4 6.36 0.00
6.5 6.48 0.00
6.6 6.57 0.08
6.7 6.58 0.28
6.8 6.58 0.54
6.9 6.59 0.91
7.0 6.59 0.94
7.1 6.59 1.17
7.2 6.60 1.37
7.3 6.60 1.60
7.4 6.60 1.84
7.5 6.61 1.94
7.6 6.61 2.26
7.7 6.61 2.52
7.8 6.61 2.68
7.9 6.62 2.94
8.0 6.62 3.21
4.6 Graphs
4.6.1 GRAPH TO SHOW VARIATION OF FORWARD CURRENT WITH VOLTAGE
FOR SILICON DIODE
3.5
Forward current (mA)
2.5
1.5
0.5
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
Voltage (V)
4.6.2 GRAPH TO SHOW VARIATION OF FORWARD CURRENT WITH VOLTAGE
FOR GERMANIUM DIODE
4
Forward current(mA)
3.5
2.5
1.5
0.5
0
0.05 0.1 0.15 0.2 0.25 0.3 0.35
Voltage (V)
4.6.3 V-I CHARACTERISTIC GRAPH FOR ZENER DIODE
4.5
4
Current(mA)
3.5
2.5
1.5
0.5
0
0 1 2 3 4 5 6 7 8 9
Voltage (V)
4.7 Analysis/discussion of results
4.7.1 Comparison of reverse current and forward current for silicon and germanium
Diodes
The value of forward current of the diodes is greater than the reverse current since the
current flow is caused by majority charge carriers when a diode is connected in forward bias
4.7.2 Comments on the characteristic graphs for silicon and germanium diodes
The curve indicates the properties of the P-N junction, before the barrier potential
voltage is reached the current is almost zero, but once the barrier potential is reached the PN
junction conducts current as seen on the above graphs
4.7.3 Comments on the characteristic graph for zener diode
Zener diode works on reverse bias, when a reverse voltage is applied a small reverse
saturation current flows this is due to minority carriers, as the reverse voltage increases the
reverse current increases sharply , this is an indication that break down has occurred
4.8 Conclusion
Different types of diodes have different characteristic graphs due to their respective level of
doping
4.9 Remarks/recommendation
The Zener breakdown voltage observed in the experiment was 6.2 Volts
4.10 Additional concepts
Applications of Zener diode
-Used as a voltage regulators
-Used in clipping circuits
-used in switching application
-Used in suppression voltage.
5. REFERENCES
(1) V.K Mehta & R. Mehta (1999), ʽ S. Chand’s Principles of Physics-XII ,
S. Chand publishing, India.
(2) M. NELKON (1970), ʽ Advanced level Physics’, Heinemann Educational Books, 48
Charles street , London.
