ELECTRONICS

ELECTRONICS

Electronics is the branch of physics which deals with development of electron emitting devices, there use and control of electron flow in electrical circuits. Electronics also deals with semiconductors, diode, rectifiers etc.

RECTIFIER

A rectifier is a device which is used to convert alternating current (AC) into direct current (DC).

PN-junction diode is used as a rectifier.

RECTIFICATION

The process of converting alternating current into direct current is called rectification.

DOPING

Addition of an element of group 3rd-A or 5th-A to Ge or Si crystals to convert them into semiconductor substance (p-type or n-type) is called Doping. Normally impurity is in very small quantity. There are two types of impurities that are added to geranium or silicon:

• Donor impurity
• Acceptor impurity

PN - JUNCTION DIODE OR SEMICONDUCTOR DIODE

INTRODUCTION  

A pn - junction diode is an electronic device formed from a p-type and an n-type substance semiconductor. A semiconductor diode has the property of one way conduction i.e. it allows electric current to flow in only one direction.

WORKING OF pn-JUNCTION DIODE

As we know that a p-type substance has excess of mobile positive charge or holes and n-type substance has an excess of negative charge or electrons, the electrons from n-type and holes from p-type sections flow across the junction and combine. In this way a layer of positive charges is formed on the n-type and a layer of negative charges on p-type material.

Due to induction of these layers a potential barrier is now developed across the junction and further flow of charges is prevented from one side to the other.

TRANSISTORS

A three terminal semiconductor electronic device is called transistor. Transistors are widely used in electronic appliances such as computers, radio, audio video equipment, bio medical instrument etc.

TYPES OF TRANSISTORS

• pnp-Transistors
• npn-Transistors

ESSENTIAL PARTS OF TRANSISTORS

There are three essentials parts of a transistor

Base:

It is the central layer denoted by b.

Emitter:

It is the outer layer denoted by e.

Collector:

It is the outer layer denoted by c.

Therefore only few holes combine with electrons and the remaining holes cross into the collector and generates collector current Ic. In this way almost the entire emitter current flows in the collector circuit. From the above description it is clear that:

Ie = Ib + Ic

Thus there are two current paths through a transistor. One is the base-emitter path or input and the other is the collector-emitter path or output.