Page 101 - Physics - XII

2. Plot the reverse voltage (V ) along the negative X-axis and the corresponding current (I ) along the
R
R
negative Y-axis. Locate the breakdown voltage (V ) and determine the revere saturation current (I ).
sat
br
I (mA)
F
100

80
Forward
60 biasing

40

20 Knee voltage (V )
100 80 60 40 20 th
V (volt) V (volt)
R 0.2 0.4 0.6 0.8 1.0 F
10
Reverse
breakdown 20
voltage (V )
br
30

I (µA)
R
Fig. 9.4: Current-voltage (I-V) characteristic curve for p-n junction diode in forward bias and reverse bias

Result

1. The value of threshold voltage for given diode, V = _____ V
th
2. The reverse saturation current for the given diode, I = _____ µA
sat
Precautions

1. Before connecting the wires, their ends should be cleaned with the help of sand paper to remove the
insulation.
2. All connections in circuit should be tight.
3. The voltmeter, milliammeter, and microammeter should be of suitable range and the current and voltage
should not exceed beyond their limits.
4. The key should be opened when the circuit is not being in use and it should be opened only at the time
of taking observations.
5. Find out manufacturer's specifi cation for maximum current through the diode in forward bias voltage.

Never exceed this limit or else the diode may get damaged.
6. Find out manufacturer's specifi cation for maximum reverse voltage to be applied to the diode in reverse
bias. Never exceed this limit.
7. The potential diff erence (V) across the diode should be increased gradually in small steps (0.1 V). Take
care that the current should not exceed beyond the specifi ed limit.

Sources of Error

1. The forward voltage may be applied beyond the tolerance limit (or a limit specifi ed on a diode) of
the diode.
2. The connections in circuit may be loose.

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