EXPERIMENT NO. 11

AIM:- A study of characteristics of light emitting diode (LED).

APPARATUS :- LED, Ammeter (0-50 mA), Voltmeter (0-10 V), DC power supply, Rheostat

CIRCUIT DIAGRAM:-

PROCEDURE:- Make the connections as shown in circuit diagram. Switch on the power supply. The voltage is set at 0 V and the current through the LED shown by milliammeter is recorded. With the help of slider of rheostat, the voltage is increased in steps of 0.2 V. For each setting of the voltage, corresponding current shown by the microammeter is noted. The observatuions are recorded in table.

OBSERVATIONS:-

Forward Voltage (Volts)

Forward Current (mA)

0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8

 
 
 
 
 
 
 
 
 
 

GRAPH:-

The graph is plotted, by taking forward voltage on the positive x axis and forward current on the positive y axis

RESULT:-

1. The LED characteristics are similar to pn-junction forward characteristics.
2. The cut-in voltage (the voltage at which conduction begins) for LED is      Volts.

PRECAUTIONS:-

1. Make sure that the connections are tight.
2. Take care to apply suitable forward voltages across the LED so that suitable forward currents flow through the LED. Otherwise the LED may be damaged.