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Type:
**Practical**Institute:
**
Anna university
**Specialization:
**Electrical and Electronics Engineering**Views:
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LIST OF EXPERIMENTS
ELECTRONICS CIRCUITS LABORATORY
LTPC
1.
Characteristics of semiconductor diode and zener diode .
2.
Characteristics of transistor under CE, CB and CC .
3.
Characteristics of FET .
4.
Characteristics of UJT .
5.
Characteristics of SCR, DIAC and TRIAC.
6.
Photodiode, Phototransistor characteristics and study of light
activated relay circuit.
7.
Static characteristics of Thermistors.
8.
Single phase half wave and full wave rectifiers with inductive and
capacitive filters.
9.
Differential amplifiers using FET.
10.
Study of CRO.
11.
Series and parallel resonance circuits.
12.
Realization of passive filters.

Ex.No.1a
CHARACTERISTICS OF PN JUNCTION DIODE
AIM:
To study the PN junction diode characteristics under Forward & Reverse
bias conditions.
APPARATUS REQUIRED:
S.No.
1
2
3
Name
Range
COMPONENTS REQUIRED:
Type
Qty
R.P.S
Ammeter
Voltmeter
S.No.
Name
1
Diode
2
Resistor
3
4
Range
Type
Bread
Board
Wires
THEORY:
A PN junction diode is a two terminal junction device. It conducts only in
one direction (only on forward biasing).
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
carriers results in the current flow, opposite to the direction of electron
movement.
Qty

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.
PROCEDURE:
FORWARD BIAS:
1. Connect the circuit as per the diagram.
2. Vary the applied voltage V in steps of 0.1V.
3. Note down the corresponding Ammeter readings I.
4. Plot a graph between V & I
OBSERVATIONS
1. Find the d.c (static) resistance = V/I.
2. Find the a.c (dynamic) resistance r = V / I (r = V/I) =
V2 V1
.
I 2 I1
3. Find the forward voltage drop = [Hint: it is equal to 0.7 for Si and 0.3 for
Ge]
REVERSE BIAS:
1. Connect the circuit as per the diagram.
2. Vary the applied voltage V in steps of 1.0V.
3. Note down the corresponding Ammeter readings I.
4. Plot a graph between V & I
5. Find the dynamic resistance r = V / I.

FORMULA FOR REVERSE SATURATION CURRENT (IO):
Io = I/[exp(V/VT)]-1
Where VT is the voltage equivalent of Temperature = kT/q
-k is Boltzmann’s constant, q is the charge of the electron
and T is the
temperature in degrees Kelvin.
=1 for Silicon and 2 for Germanium
CIRCUIT DIAGRAM:
FORWARD BIAS:
470
(0-10)V
RPS
+
+
(0-100)mA, MC
+
a +
a
a
a
a
A
A
A
+
(0-15)V, MC
+
REVERSE BIAS:
(0-500)µA,MC
470
(0-30)V
RPS
+
+
+
a +
a
a
a
a
A
A
A
Specification for 1N4001: Silicon Diode
Peak Inverse Voltage: 50V
+
+
(0-30)V, MC

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