1 1 module-1 pn junction diode. institute of applied technology fujairah 2 introduction...

1A. ALIA. ALI

INSTITUTE OF APPLIED TECHNOLOGYINSTITUTE OF APPLIED TECHNOLOGY

FUJAIRAHFUJAIRAHINSTITUTE OF APPLIED TECHNOLOGYINSTITUTE OF APPLIED TECHNOLOGY

FUJAIRAHFUJAIRAHG-11G-11

SECOND SEMESTERSECOND SEMESTER

ELECTRONICSELECTRONICS

G-11G-11

SECOND SEMESTERSECOND SEMESTER

ELECTRONICSELECTRONICS

Module-1Module-1PN Junction PN Junction

DiodeDiode


FUJAIRAHFUJAIRAH 22A. ALIA. ALI

INTRODUCTIONINTRODUCTION

Semiconductor devices, made electronics physically

very small, for example:

Computers.

certain types of medical diagnostic and treatment

equipment.

popular telecommunication devices.



DefinitionDefinition

Define the term Diode.

Diode is a PN junction semiconductor device that

allows current to flow in only one direction.

How does the current flow in the Diode?

The current flows when the Anode (A) is made positive

with respect to the Cathode (K).



Diode ConstructionDiode Construction Diode is created by doping a single piece of pure semiconductor

so that half is N-type and the other half is P-type as shown below.

It has two electrodes and hence the name diode.

(di two and ode electrode).

The electrode connected to the P-type is called Anode “A” and

that connected to N-type is called Cathode “K”

Anode (A)

Cathode (K)

N-TYPE

Electrons

+

Diode Structure

P-TYPE

Holes



Diode SymbolDiode Symbol The symbol of diode is shown below.

The cathode (K) is marked with a silver color band as

shown below.

K

Diode Symbol

A

Typical Diode

K

In the symbol, the arrow points from anode (A) to

cathode (K), this is the direction of current flow.



Types of DiodeTypes of Diode Commonly diodes are made of Silicon (Si) or Germanium (Ge).

According to the application they are classified into:

a) Low power diodes.

b) Light Emitting Diodes (LEDs).

c) Zener diodes.

d) Rectifier diodes.



Diode PackingDiode Packing Diode is generally mounted in one of the three basic

packages as shown below.

The function of the package is to protect the diode

from mechanical stress and environment

The size of the package indicates the current rating

(larger size means higher current rating).

Diode packing types

DO-41

DO-5

DO-8



Diode IdentificationDiode Identification In order to distinguish between diodes, each type is

given a unique code so that it can be identified.

There are two main semiconductor numbering

systems in use:

a) Pro-Electron System: originated and widely used in

Europe.

b) JEDEC System: widely used in North America.



Diode IdentificationDiode Identification

Pro-Electron Coding System

First Letter Specifies

Semiconductor Material

Second Letter Specifies type

of Diode

A Germanium A Low power or signal

B Silicon P Light detector

EXAMPLE: BZY74-C6V3

B = Si, Z = Zener diode, Y74 =

Commercial or Industrial use,

C = 5% of rating voltage.

6V3 = 6.3 Volt (Rating Voltage)

Q (LED)

Y Rectifier

Z Zener (V- reference)



Diode IdentificationDiode Identification

JEDEC Numbering or Coding System

First Number Second LetterSubsequent

numbers

1 Diode N Semiconductor Serial number

2Bipolar Transistor Example: This code “1N4001”

means:

1 Diode, N Semiconductor

4001 Serial number

3 FET

4 & 5Photo Coupler



Diode OperationDiode OperationForward Biased:

The diode is forward biased (FB) when the (A) is

positive with respect to the (K).

The diode in FB allows the current to flow from A to K

as shown below

Diode Operated in FB Direction

+

K

DCA

RIFIF



Diode OperationDiode OperationReverse Bias:

The diode is reverse biased (RB) when the (A) is

negative with respect to the (K).

The diode in RB does not allow the current to flow as

shown below.

Diode Operated in RB Direction

+KDC

A

R



Testing the DiodeTesting the DiodeTesting in Forward Direction with an Ohmmeter:

Connect the Red-lead to the (A) and connect the

Black-lead to the (K) as shown below.

A good diode must display low resistance

(typically < 10) in FB.

Testing the Diode in FB Direction

IN 4001

K

Ohmmeter

A



Testing the DiodeTesting the DiodeTesting in Reverse Direction with an Ohmmeter:

Connect the Red-lead to the (K) and connect the

Black-lead to the (A) as shown below.

A good diode must display a very high resistance

(> 1000 M) in RB.

Testing the Diode in RB Direction

IN 4001

K

Ohmmeter

A



Testing the DiodeTesting the DiodeTesting in Forward Direction with a Digital Voltmeter:

Connect the Red-lead to the (A) and connect the

Black-lead to the (K) as shown below.

For a diode in a good condition the reading will be in

the range of 0.3V for Ge and 0.7V for Si.

Testing the Diode in FB Direction

IN 4001

KA

DigitalVoltmeter



Testing the DiodeTesting the DiodeTesting in Reverse Direction with a Digital Voltmeter:

Connect the Red-lead to the (K) and connect the

Black-lead to the (A) as shown below.

For a diode in a good condition the reading will be

1.5V for both Ge and Si (in some cases it shows OL).

Testing the Diode in RB Direction

IN 4001

K A

DigitalVoltmeter



Testing the DiodeTesting the DiodeWhen Testing with Analogue Voltmeter:

If both bias conditions show low resistance, then the

diode is shorted.

If both bias conditions show very high resistance, then

the diode is open circuit.

When Testing with Digital Voltmeter:

If in both cases the reading is 0V, then the PN junction

is shorted, and if it is 1.5V then the PN junction is

open.



Diode ApplicationDiode Application The diode offers very little resistance to the

current flow in the FB direction.

It offers very high resistance to the current flow in

RB.

For this reason, the diodes are used in

rectification.

What is Rectification?

It is the process of converting ac to pulsating dc.



AC Current BehaviorAC Current Behavior The AC current reverses its direction with each

alteration as shown below.

Alteration of AC current between (+ve) and (-ve)

I

I

-ve

+ve +ve

-ve Negative half-cycle

Positive half-cycle



Half Wave RectifierHalf Wave Rectifier The half-wave rectifier circuit is constructed simply by

connecting a diode between the secondary of a

transformer and the load as shown below.

Load

Half Wave Rectifier Circuit

IF

AC Input

A K



Half Wave RectifierHalf Wave Rectifier During the positive half-cycle, the diode turns ON and

connects the positive half-cycle across the load (RL).

During the negative half-cycle, the diode turns OFF (RB)

as shown below. The lamp is ON during the +ve half

cycle only.

AC Input Output

Operation of Half-Wave Rectifier

IF

A K

+

Load

+



Half Wave RectifierHalf Wave Rectifier Output Voltage

Only positive half-cycles of the AC input appear across

the load, providing a pulsating DC voltage at the output

as shown below.

Secondary Voltage (VS)

Voltage across the Load

Output of Half-Wave Rectifier Voltage

VRL

VS



The End

Of Module-1

1 1 module-1 pn junction diode. institute of applied technology fujairah 2 introduction...

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diode packing diode

diode construction diode

diode symbol

symbol of diode

types of diode

diode operation

term diode

typical diode