CB transistor characteristics by padhu8285

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									                                                                        EXPERIMENT NO. 3
                  CB- TRANSISTOR CHARACTERISTICS
AIM:
       To determine the input and output characteristics of a given CB-Transistor.

APPARATUS:-
          1.   Transistor-BC 547----------------------------------1
          2.   Resistor-1k-------------------------------------------1
          3.   Voltmeter (0-20v)-----------------------------------1
          4.   Ammeter(0-50mA) --------------------------------2
          5.   R.P.S(0-30v)- ----------------------------------------1
          6.   Bread Board------------------------------------------1
          7.   Connecting Wires ---------------------------------As per required.
FORMULAE:-
       INPUT RESISTANCE= VEB/              IC, VCB CONSTANT
       OUTPUT RESISTANCE= VCB/ IC, IE CONSTANT
       AMPLIFICATION FACTOR= IC/ IE VCB CONSTANT.

THEORY:-
       Common base configuration is also called as grounded base configuration. In this emitter
made, emitter is input terminal, collector is the output terminal to the input and output circuits.

INPUT CHARACTERISTICS:-
       The input characteristics are obtained by plotting the emitter voltage VBE against IE with
VCB as parameter. A study of input characteristics reveals that there exists a cut in offset or
threshold voltage Vo, below which emitter current is very small. It is approximately 0.1v for Ge
and 0.5v for Si transistors. When VCB is equal to zero and the emitter base junction is forward
biased diode, so that IE increasing rapidly with small increase in VBE.When VCB is increased
keeping VBE constant. The width of the base region will decrease this effect results in increase
of IE. The curve shifts towards the left as VCB is increased.




OUTPUT CHARACTERISTICS:-
       The output characteristics are obtained by plotting the collector voltage VCB against IC
with IE as parameter, form the characteristics it is obvious that for constant IE.IC is independent
of VCB.Further IC flows even when VCB=0.As the emitter base junction is forward biased, the
majority carriers i.e., electrons form the emitter are injected into base region due to internal
potential barrier junction at reverse biased collector base region junction they flow to the
collector region and give rise to IE even when VCB=0.

PROCEDURE:-
INPUT CHARACTERSTICS:
   1. To determine the input characteristics, the collector based voltage VCB is kept constant
       at zero volt and the emitter current IE is increased form zero volt and the emitter current
       IE is increased form in suitable equal steps by increasing VCB.
   2. This is represented for higher fixed values of VCB.
   3. A graph is drawn between IE and VEB at constant VCB.

OUTPUT CHARACTERSTICS:-
   1. To determine the output characteristics IE is kept constant at suitable value by adjusting
       the emitter base voltage VEB.
   2. Then Vcb is increased in suitable equalsteps and the collector current Ic is noted for equal
       value of Ie. This is repeated for different values of Ie.
   3. Now, the curves of Ic versus VCB are plotted for constant values of IE and the output
       characteristics are obtained.
   4. From this output characteristics.

RESULT:- INPUT RESISTANCE R1=
                 OUTPUT RESISTANCE R0=
CIRCUIT DIAGRAM:-



                                                            Q1
          R1         _             +             C       BC547BP E
                           A                                                         A
         1kΩ
                         (0-50mA)                        B                         (0-50mV)

_ _       V                                                                                   V
                                                                                              (0-30V)
      0-30 V
                                       V   (0-20V)                   V   (0-20V)
  +                                    +




SYMBOL OF TRANSISTOR:



               c
 B             BC547BP

           E

        PIN DETAILS OF TRANSISTOR :
                            BC 547B


                   BC
                   107
                                                     E       C
               C     B         E                         B
MODEL GRAPH:-
INPUT CHARACTERISTICS :-
    IE in mA         VCB = 0V VCB = 1V VCB = 2V




                             VBE (V)
OUTPUT CHARACTERISTICS:-

                                                  IE =

                                                         IE =

IC in (mA)
                                                         IE =




                                         VBE (V)

								
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