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The only thing that will stop you

from fulfilling your dreams is you.

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Industrial Electronics

Atom

Valance electron

Due to

Shell An energy band in which electrons orbit the nucleus of an atom

Classification of matter based on semiconductor theory.

Conductor

Insulator

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Semiconductor

and germanium

Energy Band.

The band formed by the energy levels. There are main two types.

1. Valance band.

2. Conduction band.

Valance Band.

The band formed by energy level with valance electrons is known as valance band.

Conduction Band.

When an electron acquires enough additional

Energy Gap.

energy gap.

Conduction band is empty in case of insulators.

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Atomic Structure Of Silicon And Germanium.

Covalent bond.

Each silicon atom position itself with four adjacent silicon atoms

tron produce the covalent bond.

Silicon Crystal.

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becoming a free electron. When an electron jump to conduction band vacancy is left in

the valance bond with in the crystal. This vacancy is known as hole.

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Doping Since semiconductors are generally poor conductors, their conductivity can be increased

by the controlled addition of impurities to the intrinsic (pure) semi conductive material.

This process, called doping, increases the number of current carriers (electrons or holes).

The two categories of impurities are n-type and p-type.

N-Type Semiconductor

To increase the number of conduction-band electrons in intrinsic silicon, pentavalent im-

purity atoms are added. These are atoms with five valence electrons such as arsenic (As),

phosphorus (P), bismuth (Bi), and antimony (Sb).

P-Type Semiconductor To increase the number of holes in intrinsic silicon, trivalent impurity atoms are added.

These are atoms with three valence electrons such as boron (B), indium (In), and gallium

(Ga).

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Diode

A diode is made from a small piece of semiconductor material, usually silicon, in which

half is doped as a p region and half is doped as an n region with a pn junction and

depletion region in between. The p region is called the anode and is connected to a

conductive terminal. The n region is called the cathode and is connected to a second

conductive terminal.

Forward Bias If the +ve terminal of the battry is connected to the p region of the diode and the -ve

terminal is connected to the n region.

Reversed Bias If the +ve terminal of the battry is connected to the n region of the diode and the -ve

terminal is connected to the p region.

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Rectifier It is an electrical device that converts AC supply into DC and process is called

rectification. Because of their ability to conduct current in one direction and block current

in the other direction, diodes are used in circuits called rectifiers that convert ac voltage

into dc voltage.

Rectifiers are found in all dc power supplies that operate from an ac voltage source.

Rectifier circuit Rectifier circuit may be single phase or multiphase. Most low power rectifiers for

domestic equipment are single phase and 3-phase rectifier is very important for industrial

application and for power transmission.

Types 1. Single phase rectifier

I. Half wave rectifier.

II. Full wave rectifier

2. Three phase half wave circuit rectifier.

3. Three phase full wave circuit rectifier using center tapped transformer.

4. Three phase bridge circuit rectifier.

1. Single-phase rectifier

Half wave rectifier. A diode is connected to an AC source and to a load resistor, RL, forming a half-wave

rectifier. When the sinusoidal input voltage goes positive, the diode is forward-biased and

conducts current through the load resistor. The current produces an output voltage across

the load RL, which has the same shape as the positive half-cycle of the input voltage.

During the negative alternation of the input voltage, the current is 0, so the output voltage

is also 0.

The net result is that only the positive half-cycles of the ac input voltage appear across

the load. Since the output does not change polarity.

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Full Wave Rectifier.

A full-wave rectifier allows unidirectional (one-way) current through the load during the

entire of the input cycle, whereas a half-wave rectifier allows current through the load

only during one-half of the cycle.

The number of positive alternations that make up the full-wave rectified voltage is twice

that of the half-wave voltage for the same time interval.

2. Three Phase Bridge Rectifier

The bridge rectifier uses four diodes connected as shown in Figure. When the inputcycle

is positive as in part (a), diodes D1 and D2 are forward-biased and conduct current in the

direction shown. A voltage is developed across RL that looks like the positive half of the

input cycle. During this time, diodes D3 and D4 are reverse-biased.

When the input cycle is negative diodes D 3 and D 4 are forward-biased and conduct

current in the same direction through RL as during the positive half-cycle.

During the negative half-cycle, D1 and D2 are reverse-biased. A full-wave rectified

outputvoltage appears across RL as a result of this action

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