Download Experiment Name: To study the diode characteristics curve.

Experiment No : 03
Experiment Name: To study the diode characteristics curve.
Objectives:
1. I-V- characteristics of normal and zener diode.
2. To find cut-in Voltage for Silicon P-N Junction diode.
3. To find static and dynamic resistances in both forward and reverse biased
conditions for P-N Junction diode.
Apparatus Required:
1. Variable resistance
2.Resistance
3.Silicon diode
4.Ammeter
5.Voltmeter (DC)
7. Bread board and
8.connecting wires
Theory:
The diode is a device formed from a junction of n-type and p-type semiconductor
material. The lead connected to the p-type material is called the anode and the lead
connected to the n-type material is the cathode. In general, the cathode of a diode is
marked by a solid line on the diode.
Fig: Doide
Forward Bias:
On forward biasing, initially no current flows due to barrier potential. As the
applied potential exceeds the barrier potential the charge carriers gain sufficient
energy to cross the potential barrier and hence enter the other region. The holes,
which are majority carriers in the P-region, become minority carriers on entering
the N-regions, and electrons, which are the majority carriers in the N-region,
become minority carriers on entering the P-region. This injection of Minority.
Reverse Bias:
On reverse biasing, the majority charge carriers are attracted towards the
terminals due to the applied potential resulting in the widening of the depletion
region. Since the charge carriers are pushed towards the terminals no current
flows in the device due to majority charge carriers. There will be some current in
the device due to the thermally generated minority carriers. The generation of
such carriers is independent of the applied potential and hence the current is
constant for all increasing reverse potential. This current is referred to as
Reverse Saturation Current (IO) and it increases with temperature. When the
applied reverse voltage is increased beyond the certain limit, it results in
breakdown. During breakdown, the diode current increases tremendously.
Circuit diagram:
Procedure:
Diode Testing:
1- Insert the two leads of the Diode 1N7004 to the breadboard.
2- Turn on the DMM and configure it to diode test . Plug a black test lead into the
Common (−) banana socket and a red test lead into the V(+) banana socket
of the DMM.
3- Put the leads (black and red) to both terminals of the diode, and then check the
DMM reading.
4- Determine if the diode is working well or not.
Forward Bias Mode:
1. Construct the circuit shown in Figure By using 1N7004Si
diode. (Make sure your diode has the correct polarity).
2. Connect the circuit as per the diagram.
3. Vary the applied voltage V in steps of 0V-1V.
4.By the multimeter measure the current and voltage
5. Note down the corresponding Ammeter readings I.
6. Plot a graph between V & I
Reverse Bias Mode:
1- Reverse the polarity of the DC power source (VS) as shown in Figure 2.
2.Vary the applied voltage V in steps of 1.0V.
3. Note down the corresponding Ammeter readings I.
4. .By the multimeter measure the current and voltage
5. Plot a graph between V & I.
Table:Forward & Reverse Current
Voltage
V
0
.2
.3
.4
.5
.6
.7
Plotting curve:
Forward current
I mA
0
0
.02
.27
1.4
5.44
13.18
Voltage
V
0
2.5
7.6
17.1
Reverse current
I mA
0
0
0
.01
14
12
current I
10
8
6
Figure :I-V curve
(Forward Bias)
4
2
0
0
0.2
0.4
0.6
0.8
voltage v
0
-20
-15
-10
-5
-0.1
0
-0.2
Axis Title
-0.3
-0.4
-0.5
I-V (Reverse Biase)
-0.6
-0.7
-0.8
Axis Title
-0.9
Results: In forward bias, Current I increases directly in proportion to applied voltage V. In reverse
bias, when diode is break down, current increases directly on a sudden.
Discussion:
1.Current through Silicon based diode starts increasingly exponentially when potential across diode
is approximately millivolts (Cut-in Voltage).
2.With forward bias, current increases as the voltage increases.
3. With reverse bias, reverse current is minimal until avalanche conduction is reached.
4. Forward bias allows a diode to conduct.
5. Reverse bias blocks conduction, or cuts off a diode.
Precaution:
1. Connections should be right & tight.
2. Forward characteristics and reverse characteristics have been plotted in figure respectively.
3. Always take accurate reading.
4. Meters used should be without error.
5. Be alert while doing practical.