2. 2
CONTENTS
Semiconductors
What are P-type and N-type
semiconductors??
What are Diodes?
Forward Bias & Reverse Bias
Characteristics Of Ideal Diode
I – V Characteristics of Diodes
Rectification
Applications 2
3. INTRODUCTION
• Semiconductors are materials whose electrical properties lie between
Conductors and Insulators.
• Ex : Silicon and Germanium
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6. DOPING PROCESS
Doping is a process of adding a
certain amount of specific impurities
called dopants to a pure
semiconductor to increase its
electricity conductivity.
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7. P-TYPE SEMICONDUCTOR
A p-type semiconductor is an intrinsic
semiconductor doped with boron (B) or indium
(In). Silicon of Group IV has four valence
electrons and boron of Group III has three valence
electrons.
If a small amount of boron is doped to a single
crystal of silicon, valence electrons will be
insufficient at one position to bond silicon and
boron, resulting in holes* that lack electrons.
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8. N-TYPE SEMICONDUCTOR
An n-type semiconductor is an intrinsic semiconductor
doped with phosphorus (P), arsenic (As), or antimony
(Sb) as an impurity. Silicon of Group IV has four
valence electrons and phosphorus of Group V has five
valence electrons.
If a small amount of phosphorus is added to a pure
silicon crystal, one of the valence electrons of
phosphorus becomes free to move around (free
electron*) as a surplus electron.
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9. DIODES
• Electronic devices created by
bringing together a p-type
and n-type region within the
same semiconductor lattice.
Used for rectifiers, LED etc.
• It is represented by the
following symbol, where the
arrow indicates the direction
of positive current flow.
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10. PN JUNCTION
• A p-n junction is formed when a n-type and
p-type semiconductors are joined together.
• The boundary between the p-type and n-type
regions is called the junction.
• At the p-n junction, electrons from the n-side
move to the p-side and recombine with the
holes.
• Holes from the p-side similarly move into
the n-side, where they recombine with
electrons.
• As a result of this flow, the n-side has a net
positive charge, and the p-side has a net
negative charge. 10
11. What is Depletion region?
• The region around the junction
is left with neither holes nor
free electrons.
• This neutral region which has
no charge carriers is called the
depletion layer.
• This layer which has no charge
carrier is a poor conductor of
electricity.
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12. FORWARD BIAS
• Forward Bias :Forward bias or biasing is
where the external voltage is delivered
across the P-N junction diode. In a forward
bias setup, the P-side of the diode is
attached to the positive terminal and N-side
is fixed to the negative side of the battery.
• Here, the applied voltage is opposite to the
junction barrier potential
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13. REVERSE BIAS
• When we apply the external voltage across
the semiconductor diode in such a way that
the positive terminal of the battery is
connected to its n-side and the negative
terminal of the battery is connected to the
p-side of the diode, then it is said to be in the
condition of reverse bias
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14. CHARACTERISTICS OF DIODE
• Diode always conducts in
one direction.
• Diodes always conduct
current when “Forward
Biased” ( Zero resistance) .
• Diodes do not conduct when
(Reverse ).
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16. RECTIFICATION
• Converting ac to dc is
accomplished by the process
of rectification.
• Two processes are used:
1. Half-wave rectification;
2. Full-wave rectification.
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17. HALF- WAVE
RECTIFICATION
• Simplest process used to convert ac
to dc.
• A diode is used to clip the input
signal excursions of one polarity to
zero.
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18. BRIDGE RECTIFIER
• A bridge rectifier is a type of
full wave rectifier which
uses four or more diodes in a
bridge circuit configuration
to efficiently convert the AC
to DC.
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