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Wednesday, October 5, 2011

1. P-N JUNCTION DIODE CHARACTERISTICS


P-N JUNCTION DIODE CHARACTERISTICS

AIM:-To observe and draw the Forward and Reverse bias V-I Characteristics of a P-N Junction diode.
APPARATUS:-

                      P-N Diode IN4007.
                      Regulated Power supply (0-30v)
                      Resistor 1KΩ
                      Ammeters (0-200 mA, 0-500mA)
                      Voltmeter (0-20 V)
                      Bread board
                      Connecting wires
THEORY:-
                            A p-n junction diode conducts only in one direction. The V-I characteristics of the diode are curve between voltage across the diode and current through the diode. When external voltage is zero, circuit is open and the potential barrier does not allow the current to flow. Therefore, the circuit current is zero. When P-type (Anode is connected to +ve terminal and n- type (cathode) is connected to –ve terminal of the supply voltage, is known as forward bias. The potential barrier is reduced when diode is in the forward biased condition. At some forward voltage, the potential barrier   altogether eliminated and current starts flowing through the diode and also in the circuit. The diode is said to be in ON state. The current increases with increasing forward voltage.
                When N-type (cathode) is connected to +ve terminal and P-type (Anode) is connected     –ve terminal of the supply voltage is known as reverse bias and the potential barrier across the junction increases. Therefore, the junction resistance becomes very high and a very small current (reverse saturation current) flows in the circuit. The diode is said to be in OFF state. The reverse bias current due to minority charge carriers.


CIRCUIT DIAGRAM:-
FORWARD BIAS:-

REVERSE BIAS:-







MODEL WAVEFORM:-


PROCEDURE:-
FORWARD BIAS:-

1.  Connections   are made as per the circuit diagram.
2.  For forward bias, the RPS +ve is connected to the anode of the diode and  
     RPS –ve      is connected to the cathode of the diode,
3. Switch on the power supply and increases the input voltage (supply voltage) in
    Steps.
4. Note down the corresponding current flowing through the diode and voltage
    across the diode for each and every step of the input voltage.
5. The reading of voltage and current are tabulated.
6.  Graph is plotted between voltage and current.


OBSERVATION:-

S.NO
APPLIED VOLTAGE (V)
VOLTAGE ACROSS DIODE(V)
CURRENT THROUGH DIODE(mA)





PROCEDURE:-
REVERSE BIAS:-
 1. Connections are made as per the circuit diagram
2 . For reverse bias, the RPS +ve is connected to the cathode of the diode and
     RPS –ve is connected to the anode of the diode.
3. Switch on the power supply and increase the input voltage (supply voltage) in
     Steps
4. Note down the corresponding current flowing through the diode voltage
     across the diode for each and every step of the input voltage.
5. The readings of voltage and current are tabulated
6. Graph is plotted between voltage and current.
OBSEVATION:-

S.NO
APPLIEDVOLTAGE ACROSSDIODE(V)
VOLTAGE ACROSS DIODE(V)
CURRENT THROUGH DIODE(mA)






PRECAUTIONS:-

1. All the connections should be correct.
2. Parallax error should be avoided while taking the readings from the Analog meters.

RESULT:-    Forward and Reverse Bias characteristics for a p-n diode is observed

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