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
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3. INTRODUCTION
• Semiconductors are materials whose electrical properties lie between
Conductors and Insulators.
• Ex : Silicon and Germanium
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7. 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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8. 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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9.
10. 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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12. 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
13. 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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14. 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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15. 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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16. 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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17. 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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19. RECTIFICATION
• Converting ac to dc is
accomplished by the process
of rectification.
• Two processes are used:
Half-wave rectification
Full-wave rectification.
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20. 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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21. 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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