NV6000
Experiment 8
Objective:
Study of the characteristics of:-
Semiconductor diode
Schottky Diode
Theory:
Semiconductor Diode: A diode is an electrical device allowing current to move through it in one direction with
far greater ease than in the other. The most common type of diode in modem circuit design is the semiconductor
diode, although other diode technologies exist. Semiconductor diodes are symbolized in schematic diagrams as
shown below
Figure 25
When placed in a simple battery-lamp circuit, the diode will either allow or prevent current through the lamp,
depending on the polarity of the applied voltage:
Figure 26
When the polarity of the battery is such that electrons are allowed to flow through the diode, the diode is said to
be forward-biased. Conversely, when the battery is "backward" and the diode blocks current, the diode is said
to be reverse biased. A diode may be thought of as a kind of switch: "closed" when forward-biased and "open"
when reverse-biased.
V-I Characteristic:
The static voltage-current characteristics for a P-N Junction diode are shown in figure
Forward Characteristic:
When the diode is in forward-biased and the applied voltage is increased from zero, hardly any current flows
through the device in the beginning. It is so because the external voltage is being opposed by the internal barrier
voltage VB whose value is 0.7 V for Si and 0.3 V for Ge. As soon as VB is neutralized, current through the diode
increases rapidly with increasing applied supply voltage. It is found that as little a voltage as 1.0 V produces a
forward current of about 50mA.
Reverse Characteristic:
When the diode is reverse-biased, majority carrier are blocked and only a small current (due to minority carrier)
flows through the diode. As the reverse voltage is increased from zero, the reverse current very quickly reaches
its maximum or saturation value Io which is also known as leakage current. It is of the order of nanoamperes
(nA) and microamperes (A) for Ge.
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NV6000
Procedure:
1. Connect the circuit as shown in figure 27.
Figure 27
a. Connect +ve terminal of DC power supply to one end of potentiometer & Connect middle terminal of
potentiometer to one end of resistor 1K.
b. Connect other terminal of resister to +ve end (Black end) of diode IN4007 & Connect –ve terminal of
DC power supply to other end of potentiometer.
2. Now rotate the potentiometer fully clockwise position.
3. Connect one multimeter (at voltmeter range) point A & B it means across the diode.
4. Now connect the multimeter (as ammeter) between –ve terminal of diode & ground, it means we have to
connect it in series with diode.
Figure 28
5. Switch „On‟ the power supply.
6. Vary the pot so as to increase the value of diode voltage VD in the steps of 100mV.
7. Now record the diode current ID (mA) with corresponding diode voltage VD in table.
S. No. Diode Voltage VD Diode Current ID (mA)
8. Plot a curve between diode voltage VD and current ID as shown in figure (1st quadrant) using suitable scale
with the help of observation table. This curve is required forward characteristics of Si diode.
Figure 29
For Reverse Characteristics:
For this experiment only the polarity of diode will be reversed.
1. Measure the diode voltage VD in steps of 1 Volt and corresponding diode current same as the previous
given procedure.
2. Plot a curve between diode voltage VD and diode current ID as shown in figure 29 (3rd quadrant). This
curve is required characteristics of Si diode.
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