PN JUNCTION DIODE

CHARACTERISTICS

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.

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.

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

Forward Bias

Reverse Bias

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.

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.

Readings: Forward BiasVF in

Volts

0

IF in

m A

Reverse Bias

VR in

Volts

0

IR in A

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

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

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=