Zener
Diode
Presented by:
P Abhinaya Gayatri-
24R11A05D6
p. Likithaksh- 24R11A05D7
P. Harini- 24R11A05D8
Introductio
n
A Zener diode is a special type of
semiconductor diode designed to allow
current to flow not only in the forward
direction like a normal diode, but also in
the reverse direction when the voltage
exceeds a certain value known as the
Zener breakdown voltage.
Aim:
To study and plot the V-I characteristics of a zener
diode
Apparatus:
Regulated power supply (0–15 V), voltmeter (0–10 V), milliammeter (0–20
mA), microammeter (0–200 μA), p-n junction diode, Zener diode, bread
board, connecting wires.
Formulae:
Procedure
:
• Connect the Zener diode into the circuit as shown in fig. 5(c) such that it is in
reverse bias.
• Switch on the circuit. Set the reverse bias at 0V and note down the current
reading. Then the voltage is increased in steps of 1V from 0V to 6V. At each
setting of the voltage, note down the corresponding current.
• When the current suddenly tends to rise, it is set at a convenient value; say 1mA
and the voltage V<sub>Z</sub> corresponding to it is noted. The current is
then increased in steps of 1mA up to a value of 10 mA and the corresponding
voltage values are recorded. All the readings are tabulated in table II. Also note
the corresponding Zener voltage V<sub>Z</sub> values.
• The Zener diode is then connected in forward bias condition. Varying the
forward voltage in steps of 0.05V from 0V to 1V, the forward current at each
step is noted. These readings are recorded in table II.
• Using the observations, the volt-ampere characteristics of the Zener is plotted
on a graph sheet.
• The cut-in voltage is determined from the forward characteristics. The linear
part of the forward characteristics is extended down to cut the voltage axis. The
value of the voltage at the point where the straight line meets voltage axis is
the cut-in voltage.
• Determine the Zener breakdown from the reverse characteristic.
• Calculate the dynamic resistance of diode in the breakdown region.
circuit
diagram:
Observation
s:
• Note down the values of current and voltage of forward
bias.
• Note down the values of current and voltage of reverse
bias.
Graphs:
Applicatio
ns:
• VOLTAGE REGULATION: Maintains a constant output voltage despite
variations in input voltage or load conditions.
• SURGE PROTECTION: Protects sensitive electronics from over voltage
spikes acts like a clamp,conducting in reverse when voltage exceeds a
certain limits.
• WAVEFORM CLIPPING: Used in clipping circuits for remove parts of an input
signal above or below certain voltage levels useful in signal comditioning.
• SWITCHING OPERATIONS: Works as a switch in logic circuits and over
voltage detection circuits.
• VOLTAGE SHIFTING: In combination with resistors,zener diodes can
shift voltage levels in circuit like analog to digital converters.
• REFERENCE ELEMENTS: Provides a precise reference voltage in
measurement and control systems.
• METER PROTECTION: Protects measuring instruments like
voltmeters from accidental over voltages.
• PEAK CLIPPER: In communication systems to clip high amplitude
noise from signals.
Conclusion
A Z en er dio de is a speci a l type o f di o de desi gned to a l l o w current to
fl o w i n the reverse directi o n w hen the vo l tage a cro ss i t exceeds a
certai n value cal led the Z ener breakdo w n vo l tage. Un l i ke regul a r
di o des, which blo ck reverse curren t, the Zener di o de co nducts i n
reverse after this breakdo wn po i n t w i th o ut getti ng da maged.
I t i s ma i nly used for vo l tage regul a ti o n. Wh en co n nected i n reverse
bi as, i t keeps the voltage acro ss i ts termi n al s co n sta nt even i f th e
i n pu t vo ltage or load cu rren t cha nges. Th i s pro perty ma kes i t i deal fo r
pro tecti ng circuits fro m o vervo l ta ge.
Thankyou!
