A Zener diode operates in the reverse breakdown region with a sharp breakdown voltage. It is an ordinary P-N junction diode that is properly doped to have a very sharp and almost vertical breakdown. It is designed to operate exclusively under reverse bias conditions in the breakdown region without damage. The breakdown voltage can range from 2V to 800V depending on the doping level. When reverse biased, a small reverse saturation current flows until the breakdown voltage is reached, at which point the reverse current increases sharply. This breakdown voltage is called the Zener voltage and remains constant even as the Zener current increases considerably, allowing the Zener diode to be used for voltage regulation.

1. ELECTRONICS
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2. Zener Diode
The diode which operates in
the reverse breakdown
region with a sharp
breakdown voltage is called
a Zener diode
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3. Introduction
The diode which operates in the reverse breakdown region with a sharp
breakdown voltage is called a Zener diode.
It is an ordinary P-N junction diode except that it is properly doped to
have a very sharp and almost vertical breakdown. It is exclusively
operated under reverse bias conditions. It is designed to operate in
breakdown region without damage. By adjusting the doping level it is
possible to produce zener diodes with a breakdown voltage ranging
from 2V to 800 V.
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4. Zener Effect
Zener diode primarily depends for its working on Zener Effect. In a
heavily doped diode, the depletion region is very narrow. When the
reverse bias voltage across the diode is increased, the electric field
across the depletion region becomes very strong. When this field is ≈ 3
× 107 V/m, electrons are pulled out of the covalent bonds. A large
number of electron-hole pairs are thereby produced. The reverse
current rises steeply. This is Zener effect.
The diode which operates in the reverse breakdown region with a
sharp breakdown voltage is called a Zener diode.
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5. Experiment to Study the
Characteristics of the Zener Diode
Forward Bias
• A forward biasing. The voltage is varied in
regular steps of 0.1 volts by adjusting the
rheostat. The corresponding current is recorded
using a milliammeter. The readings are
tabulated. A graph is plotted taking voltage
along the x-axis and current along the y-axis.
Typical current-voltage characteristics for a
zener diode are shown in Fig. 58.9. When
forward biased, its characteristics are just that
of an ordinary semiconductor diode.
Reverse Bias
• The voltage is varied in regular steps of 1 volt by
adjusting the rheostat. The corresponding
current is recorded using milliammeter and
tabulated as shown. When reverse biased, a
small reverse saturation current flows through
it. This current remains approximately constant
until a certain critical voltage, called breakdown
voltage, is reached. Beyond this voltage, the
reverse current IR increases sharply to a high
value. This breakdown voltage Vz is called the
Zener voltage and the reverse current as zener
current. Vz remains constant even when Zener
current Iz increases considerably. This ability of
a diode is called regulating ability which enables
us to use zener diode for voltage regulation.
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6. Forward Bias Circuit
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7. Reverse Bias Circuit
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8. Schematic
Representation
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9. V – I Characteristics
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10. Thank You
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