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1. Welcome to our presentation
TOPIC : ZENER DIODE
TONMOY SAHA
2016-1-55-007
ABDUL KADER ZILANI
2016-1-55-006

2. Zener Diodes
 A Zener diode is a silicon pn junction that
is designed for operation in reverse-
breakdown region
 When a diode reaches reverse breakdown,
its voltage remains almost constant even
though the current changes drastically.
Ideally, the reverse breakdown has a constant
breakdown voltage. This makes it useful as a voltage
reference, which is its primary application.
2
Anode (A)
Cathode (K)

3. Zener Breakdown Characteristic
 As the reverse voltage (VR) increases, the reverse
current(IR) remains extremely small up to the
knee of the curve.
 Reverse current is also called Zener current(Iz).
 At knee point the breakdown effect begins, the
internal Zener resistance (ZZ) begins to decrease.
 The reverse current increase rapidly.
3

4. Zener Diode Impedence
 The zener impedance, ZZ, is the ratio of a
change in voltage in the breakdown region
to the corresponding change in current:
What is the zener impedance if the zener diode
voltage changes from 4.79 V to 4.94 V when
the current changes from 5.00 mA to 10.0 mA?
4
ZZ
VZ
–
–
+
+ Practical model
Z
Z
Z
V
Z
I



0.15 V
5.0 mA
Z
Z
Z
V
Z
I

  

30 W

5. Zener Regulation
 It maintains constant voltage of reverse current .
 Above IZM, max current, the Zener may get damaged
permanently.
5

6. Applications
 Waveform Clipper
 Voltage Regulator
 Voltage Shifter

7. Waveform Clipper
 Two Zener diodes facing each other in series will
act to clip both halves of an input signal.
 Waveform clippers can be used not only to
reshape a signal, but also to prevent voltage
spikes from affecting circuits that are connected to
the power supply.

8. Voltage Regulator
 A Zener diode can be applied in a voltage
regulator circuit to regulate the voltage applied
to a load, such as in a linear regulator.

9. Voltage Shifter
 A Zener diode can be applied to a circuit
with a resistor to act as a voltage shifter.
This circuit lowers the output voltage by a
quantity that is equal to the Zener diode's
breakdown voltage.

10. Thank YOU