This document describes the characteristics of a PN junction diode. It defines a PN junction as where a P-type semiconductor is joined to an N-type semiconductor. In forward bias, current is constant until the cut-in voltage is reached, after which it conducts. In reverse bias, current is small until the breakdown voltage is reached. The objectives are to plot the volt-ampere characteristics, find the cut-in voltage, and determine static and dynamic resistances in forward and reverse bias. The activity involves connecting a diode in a circuit and taking voltage and current readings in forward and reverse bias to generate the VI characteristics graph and calculate resistances.

1. PN JUNCTION
DIODE
CHARACTERISTICS

2. Definition
• P-type semiconductor is suitably joined to N-type
semiconductor ,to conduct surface is called PN Junction.
• In forward bias condition, current is constant until
certain voltage is reached. It is called cut in voltage. In
this condition current conduct.
• In reverse bias condition, current is constant until
certain voltage is reached. It is called breakdown
voltage. In this condition current doesn’t conduct. But
small amount of current flows in this condition due to
minority carriers.
• The undesirable free electrons in P-type and holes in N-
type are called minority carriers.

3. Objective:
To plot the Volt-Ampere characteristics of Silicon
PN Junction Diode.
To find the cut-in-voltage for Silicon PN Junction
diode.
 To find the static and dynamic resistances in both
forward and reverse biased conditions for PN
Junction diode.

4. Apparatus Required:
S.No Apparatus Type Range Quantity
(No's)
1 PN Junction
Diode
IN4001 1
2 Regulated Power
Supply
DC (0-24)V 1
3 Voltmeter MC (0-1),(0-10)V 1
4 Ammeter MC (0-100)m A,
(0-100)A
1
5 Rheostat _ 1k 1
6 Patch Cards _ _ 15
7 Connecting leads _ _ 10

5. Forward Bias

6. Reverse Bias

7. Activity Sequence:
Forward Bias:
• Connect the circuit as shown in Fig.
• Apply the supply voltage , VIN in steps of 0.1V from 0V
to0.6V
• Measure the diode voltage and current for each steps of
applied voltage VIN.
• Record the readings.

8. Activity Sequence:
Reverse Bias:
• Connect the circuit as shown in Fig.
• Apply the supply voltage , VIN in steps of 0.1V from 0V
to 15V.
• Measure the diode voltage and current for each steps of
applied voltage VIN.
• Record the readings.

9. Readings: Forward Bias
VF in
Volts
0
IF in
m A
Reverse Bias
VR in
Volts
0
IR in A

10. Model graph: Plot the reading in the graph(cm)sheet and
draw the graph for both forward and reverse bias.(Attach the
graph sheet).
Constant
voltage
Cut in
voltage
Reverse
Bias
Forward
Bias
VR in
volts
IF in mA
VF in volts
IR in A

11. Calculations: From the drawn graph calculate the static and dynamic resistance of
the given diode by selecting suitable operating point.
Formula Calculation
Static forward Resistance R dc=VF/IF 
Dynamic forward Resistance
r ac=VF/IF 
Static reverse Resistance R dc=VR/IR 
Dynamic reverse Resistance
r ac=VR/IR 

12. Result:
• Thus the VI Characteristics of PN Junction diode is
verified.
• Cut in Voltage= V
• Static forward resistance= 
• Dynamic forward resistance= 
• Static reverse resistance= 
• Dynamic reverse resistance= 