This document discusses Zener diodes. It begins by explaining that a Zener diode allows current to flow in both the forward and reverse directions, unlike a normal diode. It then provides the symbol for a Zener diode and explains how it operates in forward and reverse bias. The document notes that Zener diodes are commonly used to regulate voltage in circuits by maintaining a constant voltage regardless of changes in current or supply voltage. It concludes by listing some common applications of Zener diodes, such as in voltage stabilizers, over voltage protection circuits, and as reference elements.

1. Name : Shubhajit Chatterjee.
Student Code : BWU/BEC/19/028.
Course Name :Electronic Devices.
Course code :PCC-EC301.
Program : Bachelor of Technology in Electronics & Communication Engineering.
Semester : 3rd Semester.

2.  A diode is a specialized electronic component with two
electrode called anode and the cathode.
 Most diodes are made with semiconductor materials such
as silicon , germanium or selenium.
 The symbol of a diode is shown below. The
arrowhead points in the direction of conventional
current flow in the forward biased condition. That
means the anode is connected to the p side and the
cathode is connected to the n side.
DIODE
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3. Zener diode
 A Zener diode is a type of diode that
permits current not only in the
forward direction like a normal diode,
but also in the reverse direction if the
voltage is larger than the breakdown
voltage known as “Zener knee
voltage” or “Zener voltage”.
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4.  The arrowhead on a Zener diode
symbol points in the direction of
forward current when the diode is
forward biased.
 The Zener diode is normally
operated in reverse breakdown and
the current direction is then from
anode to cathode
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5.  The most basic Zener diode circuit consist of a single
Zener diode and a resistor.
 The Zener diode provides the reference voltage, but a
series resistor must be in place to limit the current into the
diode otherwise a large amount of current would
flow through it and it could be destroyed.
The value of resistor calculated
to give required value of current
for supply voltageused.
Zener Diode -Circuit
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Current=
𝑉1− 𝑉2
𝑅

6.  When a Zener diode is forward biased, it operates
as a normal diode.
 In forward biased P side connectedto +ve and N side
connected to –ve terminal of battery. In this case the
electrons and holes are swept across the junction an
large current flow through it.
Zener Diode – Forward bias
 The figure shows, the forward characteristics
is same as that of ordinary forward biased
junction diode.
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7. Zener Diode – Reversebiased
 In case of reverse biased current practically zero and at
certain voltage which called Zener voltage the current
increasessharply.
 Each Zener diode has breakdown ratingwhich specifies
the max voltage that can be dropped across it.
 In reverse direction however there is a very small leakage
current between 0V and the Zener voltage –i.e. tiny amount
of current is able toflow.
 Then, when the voltage reaches the breakdown voltage
(𝑉𝑍),suddenly current flow throughit.
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8. Zener Diodes are used in the "REVERSE" bias mode, i.e. the anode
connects to the negative supply, and from its I-V characteristics
curve above, we can see that the Zener diode has a region in its
reverse bias characteristics of almost a constant voltage
regardless of the current flowing through the diode. This voltage
across the diode (it's Zener Voltage, 𝑉𝑍) remains nearly constant
even with large changes in current through the diode caused by
variations in the supply voltage or load. This ability to control
itself can be used to great effect to regulate or stabilise a voltage
source against supply or load variations. The diode will continue
to regulate until the diode current falls below the minimum 𝐼 𝑍
value in the reverse breakdown region.
I-V characteristics of zener diode
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9. ELECTRONICS & COMMUNICATION
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The most common application of Zener Diode
 Zener diodes are used in Voltage stabilizers (or) shunt
regulators.
 used in Over voltage protection circuits.
 Zener diodes are used in clipping and clamping circuits
especially peak clippers .
 They are used as Reference elements.
 Used in switching applications.

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