electronics engineering

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ELECTRONICS ENGINEERING

Unit I: Semiconductor Diodes and Applications

Before we start with Electronics Let us

review the Basics of Electricity

Q. What are the two main quantities in electricity ?• CURRENT

• VOLTAGE

Unit I: Semiconductor Diodes and Applications

What is Current?

Unit I: Semiconductor Diodes and Applications

What is Voltage?

Unit I: Semiconductor Diodes and Applications

What is a Voltage Source ? A device that produces voltage output continuously.

DC Voltage Source and AC Voltage SourceTYPES:-

Unit I: Semiconductor Diodes and Applications

What is a Current Source ? A voltage source that has a very high internal

impedance as compared with external load impedance is a Constant Current Source.

• Example: A dc battery of 1000 V with internal resistance 950kΩ and load resistance varying from 50 KΩ to 150 KΩ.

7Unit I: Semiconductor Diodes and Applications

Series and Parallel Connections Two 12 V batteries in

series Two 12 V batteries in

parallel What will be the output

voltage if a 24 V battery is connected in parallel with a 12 V battery?

• The branch of engineering which deals with current conduction through a vacuum, or gas or semiconductor is known as electronics.

Applications:-•Rectification•Amplification•Control•Generation•Conversion of Light into Current•Conversion of Current into Light

Unit I: Semiconductor Diodes and Applications

Classification of Solids Insulators:

(e.g. wood, glass)

Conductors:

(e.g. copper, aluminum)

Semiconductors:

(e.g. germanium, silcon)

Conductors, Insulators and

Semiconductors

Unit I: Semiconductor Diodes and Applications

Semiconductors A semiconductor is a substance which

has conductivity (2 to 2000/ ohm-meter) in between conductors and insulators e.g. germanium, silicon, carbon etc.

A semiconductor is a substance which has almost filled valence band and nearly empty conduction band with a very small forbidden energy gap i.e. 1.1eV for silicon and 0.7eV for germanium.

Unit I: Semiconductor Diodes and Applications

Intrinsic & Extrinsic semiconductors A semiconductor in an extremely pure

form is known as an intrinsic semiconductor.

The intrinsic semiconductor has little current conduction capability at room temperature.

To be used in electronic devices, the conducting properties of intrinsic semiconductor are significantly increased by adding a small amount of suitable impurity, it is then called extrinsic semiconductor.

The process of adding impurities to a pure semiconductor is known as doping.

Man adding water to milk

12Unit I: Semiconductor Diodes and Applications

P-N Junction• If a semiconductor is doped with p-type impurities

at one end and n-type impurities at the other end, a p-n Junction is formed

13Unit I: Semiconductor Diodes and Applications

Diode It is a one way valve. It allows current to flow in one direction

only. It is commonly used (as a switch) in making

Power supply to convert ac voltage into dc voltage.

Unit I: Semiconductor Diodes and Applications

Half-wave Rectifiers

Half-wave rectifier – A diode placed in series between a transformer (or ac line input) and its load.

Unit I: Semiconductor Diodes and Applications

Positive Half-wave Rectifiers

This circuit converts an ac input to a series of positive pulses.

Unit I: Semiconductor Diodes and Applications

Negative Half-wave Rectifiers This circuit converts

an ac input to a series of negative pulses.

Unit I: Semiconductor Diodes and Applications

Full-wave Rectifier

Unit I: Semiconductor Diodes and Applications

Negative Full-wave Rectifiers

The negative full-wave rectifier converts an ac input to a series of negative pulses.

Unit I: Semiconductor Diodes and Applications

Full-Wave Bridge Rectifiers The most commonly used because:

It does not require the use of a center-tapped transformer.

It can be coupled directly to the ac power line. It produces a higher dc output than a comparable

full-wave center-tapped rectifier.

20Unit I: Semiconductor Diodes and Applications

Transistors

21Unit I: Semiconductor Diodes and Applications

Digital Circuits Digital circuits are prepared using analog

components like transistor as a switch. The binary numbers 1 and 0 are

represented by +5Volts and 0Volts.

22Unit I: Semiconductor Diodes and Applications

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