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1. PHYSICS PPT CLUB

2. DIODE :
The name diode is derived from “di–ode” which means a device that has
two electrodes.
A diode is defined as a two-terminal electronic component that only
conducts current in one direction (so long as it is operated within a
specified voltage level). An ideal diode will have zero resistance in one
direction, and infinite resistance in the reverse direction.
Semiconductor diodes are the most common type of diode. These
diodes begin conducting electricity only if a certain threshold voltage is
present in the forward direction (i.e. the “low resistance” direction).

3. DIODE :
The basic symbol of p-n junction diode under forward bias and reverse
bias is shown in the below figure

4. PN JUNCTION DIODE :
In ideal conditions, this PN junction behaves as a short circuit when it
is forward biased, and as an open circuit when it is in the reverse
biased.
PN junction diode is one of the fundamental elements in electronics.
In this type of diode, we dope one side of a semiconductor piece with
an acceptor impurity and another side with a donor impurity.

5. PN JUNCTION DIODE :
In n-type semiconductors, free electrons are the majority charge carriers
whereas in p-type semiconductors, holes are the majority charge
carriers.
When the n-type semiconductor is joined with the p-type semiconductor,
a p-n junction is formed.
The p-n junction, which is formed when the p-type and n-type
semiconductors are joined, is called as p-n junction diode.

6. BIASING OF P-N JUNCTION SEMICONDUCTOR DIODE
forward biasing
reverse biasing.
The process of applying the external voltage to a p-n junction
semiconductor diode is called biasing.
External voltage to the p-n junction diode is applied in any of the two
methods:

7. FORWARD BIASING OF P-N JUNCTION :
If the p-n junction diode is forward biased, it allows the electric current
flow. Under forward biased condition, the p-type semiconductor is
connected to the positive terminal of battery whereas; the n-type
semiconductor is connected to the negative terminal of battery.

8. REVERSE BIASING OF P-N JUNCTION :
If the p-n junction diode is reverse biased, it blocks the electric current
flow. Under reverse biased condition, the p-type semiconductor is
connected to the negative terminal of battery whereas; the n-type
semiconductor is connected to the positive terminal of battery.

9. SILICON SEMICONDUCTOR DIODES :
For designing the diodes, silicon is more preferred over germanium.
The p-n junction diodes made from silicon semiconductors works at high temperature
than the germanium semiconductor diodes.
Forward bias voltage for silicon semiconductor diode is approximately 0.7 volts
whereas for germanium semiconductor diode is approximately 0.3 volts.
Silicon semiconductor diodes do not allow the electric current flow, if the voltage
applied on the silicon diode is less than 0.7 volts.
Silicon semiconductor diodes start allowing the current flow, if the voltage applied on
the diode reaches 0.7 volts.

10. GERMENIUM SEMICONDUCTOR DIODES :
Germanium semiconductor diodes do not allow the electric current flow, if the voltage
applied on the germanium diode is less than 0.3 volts.
Germanium semiconductor diodes start allowing the current flow, if the voltage
applied on the germanium diode reaches 0.3 volts.
The cost of silicon semiconductors is low when compared with the germanium
semiconductors.

11. APPLICATIONSOF P-N JUNCTION DIODE
P-N junction diode can be used as a photodiode as the diode is sensitive to
the light when the configuration of the diode is reverse-biased.
It can be used as a solar cell.
When the diode is forward-biased, it can be used in LED lighting
applications.
It is used as rectifier in many electric circuits and as a voltage-controlled
oscillator in varactors.

12. SUMMARY OF P-N JUNCTION DIODE
Semiconductors contain two types of mobile charge carriers, “Holes” and
“Electrons”.
The holes are positively charged while the electrons negatively charged.
A semiconductor may be doped with donor impurities such as Antimony (N-
type doping), so that it contains mobile charges which are primarily
electrons.
A semiconductor may be doped with acceptor impurities such as Boron (P-
type doping), so that it contains mobile charges which are mainly holes.
The junction region itself has no charge carriers and is known as the
depletion region.

13. SUMMARY OF P-N JUNCTION DIODE
The junction (depletion) region has a physical thickness that varies with the
applied voltage.
When a diode is Zero Biased no external energy source is applied and a
natural Potential Barrier is developed across a depletion layer which is
approximately 0.5 to 0.7v for silicon diodes and approximately 0.3 of a volt
for germanium diodes.
When a junction diode is Forward Biased the thickness of the depletion
region reduces and the diode acts like a short circuit allowing full circuit
current to flow.

14. SUMMARY OF P-N JUNCTION DIODE
When a junction diode is Reverse Biased the thickness of the depletion
region increases and the diode acts like an open circuit blocking any current
flow, (only a very small leakage current will flow).

15. Thanks for Watching
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