chapter 1 part 1 2

8/2/2019 Chapter 1 Part 1 2

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INTRODUCTION TOELECTRONIC DEVICES

INTRODUCTION


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INTRODUCTION

What isElectronics ?Electronic devices ?Electronic system ?


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INTRODUCTION

The branch of physics that dealswith the emission and effects of

electrons ; and the use ofelectronic devices.

Science of the motion of chargesin a gas, vacuum orsemiconductor.

ELECTRONICS


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INTRODUCTION

An electronic building block packaged in adiscrete form with two or more connecting

leads or metallic pads.

Components are connected together to createan electronic circuit with a particular function.E.g.: an amplifier, radio receiver, or oscillator.

Active components are sometimes calleddevices.

ELECTRONICDEVICES


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INTRODUCTION

Composed of subsystems orelectronic circuits, which mayinclude amplifiers signal

sources, power supplies etc

E.g.: Laptop, DVD players,iPOD, PDA, mobile phones

ELECTRONICSYSTEM


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INTRODUCTION

What are we learning

Diodes

Bipolar Junction Transistor (BJT)

Field Effect Transistor (FET)


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SEMICONDUCTORMATERIAL

CHAPTER 1


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SEMICONDUCTOR MATERIAL

Atomic Structure

Material

Classification

Energy Band

Covalent Bonds

Conduction inSemiconductor

P-type & n-type

semiconductors


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1.1 Atomic Structure

All matters on earth made of atoms (made up ofelements or combination of elements).

All atoms consist of electrons, protons, and neutrons.

An atom is the smallest particle of an element thatretains the characteristics of that element


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Bohrs Atomic Structure

According to Bohr,atoms have a

planetary structure

that consists of acentral nucleus,

surrounded by

orbiting electrons.

Nucleus contains

protons and neutrons.

Electrons (-) orbits

the nucleus

Nucleus :

Protons (+)

Neutrons (neutral)


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Each type of atom has a certain number of electronsand protons that distinguishes it from atoms of other

elements.


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Helium Atom

Each electron has its own

orbitwhich corresponds

to different energy

levels.

Similar energy levels(orbits) are grouped into

energy bands called

shells.


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Electron Shells & Orbits

Each electron travelson its own orbit

The different orbit

corresponds todifferent energy

level.

In an atom, orbits

are grouped intoenergy bands

known as shells.

Each shell has a

fixed max no. ofelectrons at allowed

energy levels


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Energy Band Concept

The number of electrons in shell 1 -4 can be calculated as:

Ne = 2n2

Electron orbits the nucleus atcertain distances The outermost shell is called the

valence shell.

Electrons on this shell are calledvalence electrons


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Valence Electrons

The outermost shell is called the valence shell andelectrons at this layer are called valence electrons.

Valence electrons contribute to chemical reactionsand bonding within the structure of a materialand determine its electrical properties.

Maximum number of valence electron is 8. An atom is stable if it has 8 valence electrons;

eg: Neon (10), Argon (18), Krypton (36).


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Valence Electrons

The number of valence electrons determines theability of material to conduct current. The less

complete a shell is filled to capacity (max 8) the more

conductive the material is.

CONDUCTOR

1-3 valenceelectrons

More tendency toloose electrons

INSULATOR

5-8 valenceelectrons

More tendency togain electrons

SEMICONDUCTOR

Has 4 valenceelectrons

Not easy foratom to loose orgain electrons


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Valence Electrons

A Silicon atom has 4 electrons in its

valence ring. This makes it a

semiconductor.

A Copper atom has only 1 electron in

its valence ring. This makes it a good

conductor.


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1.2 Material Classification

What are the differences between semiconductors,conductors and insulators

What is the difference between silicon andgermanium semiconductor?

Why is Si more widely used compared to Ge?


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1.2 Materials Classification

Conductor Easily conducts electrical current

Insulator Does not conduct electrical current

Semiconductor

In between a conductor & an insulator In its pure (intrinsic) condition, is neither

a good conductor not a good insulator


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chapter 1 part 1 2

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