This presentation introduces Zener diodes. It discusses that a Zener diode is a silicon pn junction designed to operate in reverse breakdown, maintaining a constant voltage even as current changes. The document examines Zener breakdown characteristics, showing how reverse current increases rapidly at the knee point where breakdown begins. It provides an example calculation of Zener impedance. Applications of Zener diodes discussed include waveform clipping, voltage regulation, and voltage shifting.

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