ELECTRONICSThe word Electronics is derived from Electron Mechanics which means the study of the behavior of an electron under different conditions of externally applied fields.

Electronics is a field of Science and Engineering, which deals with electronic devices and their utilization.

Electronic device is a device in which conduction takes place by the movement of electrons ─ through vacuum, gas or semiconductors.

Applications of Electronics

Communications & EntertainmentsMedical SciencesDefence ApplicationsIndustrial ApplicationsInstrumentations

April 17, 2023 Introduction 2

Communications and Entertainments

Line CommunicationsTelegraphyTelephonyTelexTeleprinters

Wireless CommunicationsRadio broadcastingTV broadcastingFacsimile (Radiophoto)

Audio SystemsPublic Address (PA) systemsStereo amplifiersRecord playersTape recorders

April 17, 2023 Introduction 3

Medical Sciences

Electrocardiogram (ECG) Electrotherapy Modern X-rays

April 17, 2023 Introduction 4

Defence Applications

Radar guided missiles Coded communications

April 17, 2023 Introduction 5

Industrial Applications

Automatic control systems Heating and welding systems Electron Microscope Computers

April 17, 2023 Introduction 6

InstrumentationInstrumentation Precision measuring instruments

Cathode Ray Oscilloscope (CRO)Vacuum Tube Volt Meter (VTVM)Digital Volt Meter (DVM)Frequency CountersSignal generatorpH meterStrain gauge

etc.

April 17, 2023 Introduction 7

Atomic Structure

April 17, 2023 Introduction 8

Random Movement of Electronsin Aluminium atoms.

April 17, 2023 Introduction 9

Simplified Representation of Atoms

April 17, 2023 Introduction 10

Permissible Energy Levels (for an isolated hydrogen atom)

April 17, 2023 Introduction 11

Types of Materials

Conductors Semiconductors Insulators

April 17, 2023 Introduction 12

Conductors• Electrical conductivity is excellent.• Concentration of free electrons is very large ~1028

electrons/metre3.• Under the influence of an applied electric field the

electrons may acquire additional energy and move into higher states.

• The conduction and the valence band overlaps with each other.

• Have positive temperature coefficient of resistance, i.e., resistance increases with increase in temperature.

April 17, 2023 Introduction 13

Insulators

• Very poor conductor of electricity.• Concentration of free electrons is very small ~ 107

electrons/meter3.• Large forbidden band gap separates filled valence

band from the vacant band.• The energy which can be supplied to an electron

from an applied field is too small to carry the electrons from the filled to the vacant band.

April 17, 2023 Introduction 14

Semiconductors• Conductivity is in between that of conductors and

insulators.• Concentration of free electrons is moderate and is in

between that of conductors and insulators.• Width of the forbidden gap is relatively small ~

1 eV.At 0 K : Eg for Ge ~ 0.785 eV

Eg for Si ~ 1.21 eV • Band gap energy in a crystal is a function of interatomic

spacing and hence depends somewhat on temperature.• Has negative temperature coefficient of resistance, i.e.,

resistance decreases with rise ion temperature.

April 17, 2023 Introduction 15

Energy Bands

April 17, 2023 Introduction 16

Materials for Semiconductors

Germanium and Silicon, which has tetravalent atoms are the two most important semiconductors used in electronic devices.

April 17, 2023 Introduction 17

Review• Electronics.• Applications of Electronics :

– Communications and Entertainments.– Medical Sciences.– Defence Applications.– Industrial Applications.– Instrumentation.Instrumentation.

• Types of Materials :– Conductors.– Insulators.– Semiconductors.

• Atomic Structure : Energy Bands (in Na)

April 17, 2023 Introduction 18