V-I Characteristics of PN Junction Diode | Electronics Laboratory
PN Junction Diode
A diode is a PN junction formed by a layer of P-type and a layer of N-type Semiconductors.
Once formed the free electrons in the N region diffuse across the junction and combine with holes
in the P region and so it develops a depletion Layer. The depletion layer comprises ions, which acts as a barrier for diffusion of charged beyond a certain limit. The difference of potential across the
depletion layer is called the barrier potential. At 2.5degree the barrier potential approximately
equal 0.7v for silicon diode and 0.3v for germanium diode.
When the junction is forward bias, the majority carrier gained sufficient energy to overcome the barrier and the diode conducts. When the junction is reverse biased, the depletion layer widens and the barrier potential increases. Hence the Majority carrier cannot cross the Junction and the diode does not conduct. But there will be a leakage current because of minority carrier.
PROCEDURE:
FORWARD BIAS:
➢ The connections are made as per the circuit diagram.
➢ The positive terminal of the power supply is connected to the anode of the diode and negative
terminal to the cathode of the diode.
➢ Forward voltage Vf across the diode is increased in small steps and the forward current is
noted.
➢ The readings are tabulated. A graph is drawn between V f and I f.
REVERSE BIAS:
➢ The connections are made as per the circuit diagram.
➢ The positive terminal of power supply is connected to the cathode of the diode and negative
terminal to the anode of the diode.
➢ Reverse voltage Vf across the diode is increased in small steps and the Reverse current is
noted.
➢ The readings are tabulated. A graph is drawn between V r and I r.
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