This fun and visually appealing presentation about the core concept of diodes formation and application is thoroughly researched and concise. It contains fun tit-bits of info that make the concept of depletion layer easy to understand. It has a vibrant color scheme to make a perfect first impression for any project...

1. Presented by : Ishwari, Aditee & Komal
V-I CHARACTERISTICS
OF ZENER DIODE

2. INTRODUCTION
ZENER DIODE &
HOW DOES IT
WORK?
CIRCUIT
SIMULATION
Presentation Outline
APPLICATION OF
ZENER DIODE:
VOLTAGE REGULATOR

3. INTRODUCTION

4. A semiconductor is a material, typically a solid chemical
element or compound, that can conduct electricity under
certain conditions but not others, making it an excellent
medium for controlling the flow of the electrical current.
E.g. resistors, ICs, transistors etc.
WHAT ARE SEMICODUCTORS?

5. CHARACTERISTICS OF SEMICONDUCTORS
It can conduct electricity under optimal conditions.
It is an excellent material for conducting electricity in a controlled
manner. In contrast to conductors, charge carriers in semiconductors
are generated solely by external energy (thermal agitation).
It allows a certain number of valence electrons to leap into the
conduction band and cross the energy gap, leaving an equal number of
unoccupied energy states, i.e. holes. The importance of electron and
hole conduction is similar and they trigger current flow.
Resistivity: 10^-5 to 10^6 Ω m.
Conductivity: 10^5 to 10^-6 ohm/m.
Temperature resistance coefficient: Negative.

7. INTRINSIC EXTRINSIC
Parameters
Purity : Pure Impure
Density of e:
Electrical
condutivity:
Low High
Dependence on
temperature only
de ≠ dh
de = dh
Dependence on
temperature and the
amount of impurity
Temperature
effect:
Trivalent and
Pentavalent impurities
No impurities
Impurities:

8. .
E.C of Sb: [Kr] 4d10 5s2 5p3. E.C of B: [He] 2s2 2p1
E.C of Si : [Ne] 3s² 3p²

9. EXTRINSIC SEMICONDUCTORS
N-TYPE
P-TYPE
Donor impurities are used.
Trivalent impurities are used.
Holes are generated.
Holes are the majority charge
carrier and electrons are
minority charge carriers.
E.g. Boron doped Silicon,
Aluminum doped Silicon, Boron
doped Germanium etc.
Acceptor impurities are used.
Pentavalent impurities are used.
Electrons are generated.
Electrons are the majority charge
carriers and holes are the
minority charge carriers
E.g. Arsenic doped Silicon,
Phosphorus doped Silicon,
Arsenic doped Germanium, etc.

10. WHAT ARE DIODES?
A diode is a semiconductor device that essentially acts as a one-way switch
for current. It allows current to flow easily in one direction, but severely
restricts current from flowing in the opposite direction.
Diodes are rated according to their type, voltage, and current capacity.
Diodes have polarity, determined by an anode (positive lead) and cathode
(negative lead). Most diodes allow current to flow only when positive
voltage is applied to the anode.

12. Types of Diodes:

13. Depletion layer in diodes & their function
while junction is forming, electrons from the
n-side diffuse across the junction and
recombine with the holes in the p-region.
when electrons leave the n-region, they create
a +ve io and on recombining with the holes
create a -ve ion in the p-region.
Width of depletion layer 0.5μm to 1 μm
The crossing of electrons and holes created a
p.d. across the junction.
This p.d. prevents the continuous diffusion of
current, hence it is called barrier potential
At room temperature, under the equilibrium,
the approximate value of the potential barrier
is 0.7 V for silicon and 0.3 V for germanium.
Unbiased diode

14. Reverse and forward biasing

15. Depletion layer of Forward and Reversed biased
Reversed biased
Forward biased

16. WHAT IS A
ZENER DIODE?

17. Zener diode is a heavily doped PN Junction diode.
since it is heavily doped, its depletion layer is quite
thin and in order of a micrometer.
Zener diodes are a special kind of diode that
permits current to flow in the forward direction also
allow current to flow in the reverse direction when
the voltage is above a certain value.
This breakdown voltage is known as the Zener
voltage. In a standard diode, the Zener voltage is
high, and the diode is permanently damaged if a
reverse current above that value is allowed to pass
through it.

19. The peak doping concentration for p+ layer is
varied from 1015 cm−3 to 1017 cm−3 whereas the
doping level for the p-layer is fixed at 1014
cm−3or 1015 cm−3.
Both the uniform and linearly graded base
doping are considered. The dopant
concentration of the Zener diode is almost 1000
times greater as compared to a normal diode
and because of this high doping concentration
Zener diode shows different characteristics as
compared to a normal diode and acts as a
voltage regulator when operated in reverse bias.
WHAT ARE THE DOPING LEVELS FOR THE ZENER DIODE?

20. Zener effect
The Zener effect is a type of electrical breakdown that occurs in a reverse-biased PN
junction when the electric field enables tunneling of electrons from the valence to the
conduction band of a semiconductor, leading to a large number of free minority carriers
which suddenly increase the reverse current.
The Zener effect is best known for its use in the appropriately-named Zener diode.
A normal PN junction diode freely allows current flow if forward biased, but blocks the
current if it is reverse biased – a useful attribute in rectifier circuits, for example.
However, if the reverse voltage applied across such a diode becomes too high, the
device will break down and probably suffer permanent damage.
A Zener diode behaves similarly to the extent that it allows forward current but blocks it
if reverse-biased. The difference comes if the reverse voltage reaches the device’s
critical break-down value because it begins to conduct in the reverse direction. This is
due to an effect known as an avalanche breakdown, which occurs in the semiconductor
depletion layer; a current starts to flow through the diode to limit the voltage increase.

21. Avalanche Effect
The avalanche breakdown occurs when a high reverse voltage
is applied across the diode. As we increase the applied reverse
voltage, the electric field across the junction increases.
This electric field exerts a force on the electrons at the
junction and frees them from covalent bonds. These free
electrons start moving with high velocity across the junction
and collide with the other atoms, thus creating more free
electrons.
This results in a rapid increase in net current. Both these
breakdowns occur in Zener diodes.

23. CIRCUIT
SIMULATION

24. Components of the circuit
D.C source
Rheostat or
potentiometer
External p.d
Provides varying
current & resistance
Carbon
Resistor
To limit the current
thought the diode

25. milliammeter
voltmeter
An instrument used for
measuring either direct or
alternating electric current, in
milliamperes (10^-3)
Measures voltages of either
direct or alternating electric
current on a scale

26. Circuit diagram

27. ZENER DIODE :
VOLTAGE
REGULATOR

28. 220 V
50Hz
Rectifiers Filters Voltage
regulator:
Regulated DC
Step-down
Transformer
output
primary voltage
is converted to
secondary
voltage
makes the
current uni-
directional
Removes
ripples
Regulates
current
Unregulated DC

29. -
Unregulated input(Vi) regulated
output
I Rs
Vs
Iz
Vz
Rl
IL
Vo=Vz
+
From the circuit,
I = Iz + IL , Vi = Vs + Vz
Vi = IRs + Vz
Vi = V(Iz + IL)+ Vz or
Vi = V(Iz + IL)+ Vo
since Vo = Vz

30. REFERENCES
https://youtu.be/JdL3DnnFHXw
https://youtu.be/6xGCOrPBL4s
https://www.youtube.com/watch?v=EzlSafjMltc
https://www.youtube.com/watch?v=vSlU5FxStcU
https://uk.farnell.com/zener-effect-definition

31. THANK YOU FOR
LISTENING!
Don't hesitate to ask any questions!