1. Introduction
Muhammad Adeel Shakir B-21939
Topic :PN junction Diode & Rectifier

2. Learning Outcomes
 PN Junction Diode
 History Of PN Junction Diode
 What Is PN Junction Diode
 N-type material & P-type
material
 Working Of PN Junction Diode
 Advantage Of PN Junction
Diode
 Disadvantage Of PN Junction
Diode
 Uses Of PN Junction Diode
Rectifier
 Half Wave Rectifier
 Full Wave Rectifier
 What Is Bridge Rectifier
 Types of Bridge Rectifiers
 Bridge Rectifier Working Principle
 Advantage of Bridge Rectifier
 Disadvantage of Bridge Rectifier
 Application of Bridge Rectifier

3. PN Junction Diode
• Every invention has an element of “accidental” in it.
The story of PN Junction also has one! One day
morning, Russel was inspecting a quirky silicon crystal
which had a crack on its middle. The crystal was
connected to voltmeter and he noticed a sudden
change in voltage (about half volts) when he placed the
crystal over a stream of light from a lamp on his table.
Now this was something marvelous on those days. No
one has discovered such a behavior of crystals before
that.
 History Of PN Junction Diode:

4.  Gunn Diode
 Laser Diode
 Light Emitting Diode
 Photodiode
 PIN Diode
 PN Junction Diode
 Schottky Diode
 Step Recovery Diode
 Tunnel Diode
 Varactor Diode
 Zener Diode
 Different Types of Diodes

5. What Is PN Junction Diode ?
P N
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- - - - -
- - - - -
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+ + + + +
+ + + + +
+ + + + +
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Metallurgical
Junction
Space Charge
Regionionized
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ors
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e- drift= == =
P-N junction diode is the most fundamental and the
simplest electronics device. When one side of an intrinsic
semiconductor is doped with acceptor one side is made p-type by
doping with n-type material, A p-n junction diode is formed. This is
a two terminal device.

6.  N-type material & P-type material
 When extra valence electrons
are introduced into a material
. such as silicon an n-type
. material is produced.
 P-type material is produced
when the dopant that is
introduced is from Group III.
Group III elements have only
3 valence electrons and
therefore there is an electron
missing.

7.  Working Of PN Junction Diode
Because each side of the junction contains an excess of
holes or electrons compared to the other side, there
exists a large concentration gradient. Therefore, a
diffusion current flows across the junction from each
side.

8. Depletion Region
As free electrons and holes diffuse across the
junction, a region of fixed ions is left behind.
This region is known as the “depletion
region.”

9.  Current Flow Across Junction: Drift
The fixed ions in depletion region create an electric
field that results in a drift current.

10.  Diode in Reverse Bias
When the N-type region of a diode is connected to a higher
potential than the P-type region, the diode is under reverse
bias, which results in wider depletion region and larger built-
in electric field across the junction.

11.  Diode in Forward Bias
When the N-type region of a diode is at a lower potential
than the P-type region, the diode is in forward bias.
The depletion width is shortened and the built-in electric
field decreased.

12.  Constant-Voltage Diode Model
Diode operates as an open circuit if VD< VD,on and a
constant voltage source of VD,on if VD tends to exceed
VD,on.

13.  Zener Avalanche & Reverse Breakdown
Zener breakdown is a result of the large electric field
inside the depletion region that breaks electrons or
holes off their covalent bonds.
Avalanche breakdown is a result of electrons or holes
colliding with the fixed ions inside the depletion region.
When a large reverse bias voltage is applied, breakdown
occurs and an enormous current flows through the
diode.

14. Advantage
Disadvantage&
 A p-n junction diode can be used to
convert the alternating current (AC) to
the direct current (DC). These diodes
are used in power supply devices.
 If the diode is forward biased, it allows
the current flow. On the other hand, if it
is reverse biased, it blocks the current
flow.
 Distortion
 Insensitive

15.  Uses Of PN Junction Diode
 Chargers
 AM/FM Radio
 Noise reduction mic found in
smartphones
 Solar panels
 On/Off indicators
 Displays
 LASER

16. o Now we come to the most popular application of
the diode: rectification. Simply defined, rectification is the
conversion of alternating current (AC) to direct current (DC). This
involves a device that only allows one-way flow of electrons. As we
have seen, this is exactly what a semiconductor diode does. The
simplest kind of rectifier circuit is the half-wave rectifier. It only
allows one half of an AC waveform to pass through to the load.
Half-wave rectifier circuit.

17.  Full Wave Rectifier Circuit
o In a Full Wave Rectifier circuit two diodes are now used, one
for each half of the cycle. A multiple winding transformer is
used whose secondary winding is split equally into two halves
with a common centre tapped connection, (C

18.  What is a PNP Transistor?
 The term ‘PNP’ stands for positive, negative, positive and also
known as sourcing. The PNP transistor is a BJT; in this transistor
the letter ‘P’ specifies the polarity of the voltage necessary for
the emitter terminal. The second letter ‘N’ specifies the polarity
of the base terminal. In this kind of transistor, the majority
charge carriers are holes. Mainly, this transistor works as the same
as the NPN transistor.

19.  PNP Transistor Construction
 The PNP transistor construction is shown below.
The main characteristics of both the transistors
are similar except that the biasing of the current
& voltage directions are inverted for any one of
the achievable 3-configurations namely common
base, common emitter and common collector.

20.  What is an NPN Transistor?
 The term ‘NPN’ stands for negative, positive,
negative and also known as sinking. The NPN
transistor is a BJT, in this transistor, the initial letter
‘N’ specifies a negatively charged coating of the
material. Where, ‘P’ specifies a completely charged
layer. The two transistors have a positive layer, which
are situated in the middle of two negative layers.
Generally, NPN transistor is used in various electrical
circuits for switching and strengthens the signals that
exceed through them.

21.  Construction of NPN Transistor
 The construction of this transistor is shown below. The
voltage at the transistor’s base is +Ve and –Ve at the
transistors emitter terminal. The base terminal of the
transistor is positive at all times with respect to the
emitter, and also collector voltage supply is +Ve with
respect to the transistor’s emitter terminal. In this
transistor, the collector terminal is linked to the VCC
through the RL.

22.  Main Difference Between PNP and NPN
• Both the transistors are collected of special materials and the flow
of current in these transistors is also different.
• In an NPN transistor, the flow current runs from the collector
terminal to the Emitter terminal, whereas in a PNP, the flow of
current runs from the emitter terminal to the collector terminal.
• PNP transistor is made up of two P-type material layers with a
layer of sandwiched of N-type. The NPN transistor is made up of
two N-type material layers with a layer of sandwiched of P-type.
• In an NPN-transistor, a +ve voltage is set to the collector terminal
to generate a flow of current from the collector. For PNP
transistor, a +ve voltage is set to the emitter terminal to generate
flow of current from the emitter terminal to collector.

23.  What is a Bridge Rectifier?
 A Bridge rectifier is an Alternating Current (AC) to Direct
Current (DC) converter.
 Bridge Rectifiers rectifies mains AC input to DC output.
 Bridge Rectifiers are widely used in power supplies.
 It provide necessary DC voltage for the electronic components
or devices.

24.  Types of Bridge Rectifiers
 Bride rectifiers are classified into several types based on these
factors.
 Type of supply, controlling capability, bride circuit’s
configurations, etc.
 Bridge rectifiers are mainly classified into Single and Three
phase rectifiers.
 Both these types are further classified into Uncontrolled, Half
Controlled and Full Controlled rectifiers.

25.  Single Phase and Three Phase Rectifiers
 A single phase or three-phase supply
decides these rectifiers.
 The Single phase bridge rectifier
consists of four diodes for converting
AC into DC.
 A three phase rectifier uses six diodes.
 These can be again uncontrolled or controlled
rectifiers depending on the circuit components such as
diodes, thyristors, and so on.

26.  Introduction:
 A bridge rectifier circuit is a common part of the electronic
power supplies. Many electronic circuits require rectified DC
power supply for powering the various electronic basic
components from available AC mains supply.

27.  Bridge Rectifier Circuit Diagram
 The first stage of the circuit is a transformer which is a step-down type.
 It changes the amplitude of the input voltage.
 Most of the electronic projects uses 230/12V transformer to step-down
the AC mains 230V to 12V AC supply.
 Next stage is a diode-bridge rectifier which uses four or more diodes.

28.  Bridge Rectifier Working Principle
 A single-phase bridge rectifier consists of four diodes and this configuration is
connected across the load.
 During the Positive half cycle of the input AC waveform diodes D1 and D2 are
forward biased.
 Diodes D3 and D4 are reverse biased.
 When the voltage, more than the threshold level of the diodes D1 and D2, starts
conducting.
 The load current starts flowing through it. During the negative half cycle of the input
AC waveform.
 The diodes D3 and D4 are forward biased, and D1 and D2 are reverse biased.
 We can observe that in both the cases, the load current direction is same, i.e
Unidirectional, which means DC current.

29.  Advantage of Bridge Rectifier
 The main advantage of this bridge circuit is that it
does not require a special centre tapped
transformer.
 Higher output voltage, higher output power and
higher Transformer Utilization Factor (TUF) in
case of a full-wave rectifier.
 Transformer utilization factor, in case of a bridge
rectifier, is higher than that of a centre-tap rectifier.

30.  Disadvantage of Bridge Rectifier
 The main disadvantage of a bridge rectifier is that it needs
four diodes.
 Total voltage drop in diodes becomes double of that in case of
centre-tap rectifier.
 Losses are increased and rectification efficiency is somewhat
reduced.
 Another disadvantage of bridge rectifier is that the load
resistor RL and the supply source have no common point
which may be earthed.

31.  Application of Bridge Rectifier
 The main application of bridge rectifier is to convert AC
Power to DC Power.
 Because of their low cost compared to center tapped they
are widely used in power supply circuit.
 This can be used to detect the amplitude of modulated
radio signal.
 Bridge rectifiers can be used to supply polarized voltage in
welding.
welding.