Experiment 5: Input and output Characteristics of BJT

Input and output Characteristics of BJT

 Objective:- 1)Design the circuit diagram. Take the reading and draw the characteristics curve Determine the input and output resistance.

Equipments required:- 1) Voltmeter 2)Ammeter 3)Bread Board 4) 0 - 30 V dc P.S.

Components required- Resistors- 1k, 470K, 1M , Transistor (No-BC548) NPN

Theory:- The three terminals of a  BJT are Emitter (E), Collector(C) and Base (B). The Common Emitter (CE) configuration is most frequently encountered configuration. In this the emitter is common or reference to both the input and output terminals (in this case common to both the base and collector terminals). Two sets of characteristics are necessary to describe fully the behavior of the CE configuration: input and output characteristics.

The plot of base current I_B versus the voltage V_BE across its base and emitter for different values of voltage V_CE, is called the input characteristics.

Input Characteristics Circuit Diagram

 

Circuit Diagram for Input Characteristic of BJT

Procedure:-     1. Set up the circuit as shown in the diagram.

                                2. Set V_CE  at 1V.

                                3. Increase the input voltage V_BE in steps of 0.5V and note the corresponding I_B.

                                4. Repeat for V_CE = 2V

                                5. Plot the input characteristics curve with V_BE on x-axis and I_B on y-axis

 Expected Graph

VCE=1V,2V
V1	IB	VBE
0
.5V
1V
1.5V
2V
2.5V
3V
3.5
4V
4.5V
5V

 

  .
The plot of collector current I_C versus the voltage V_CE across its collector and emitter for different values of base current I_B is called the output characteristics.

Output Characteristics Circuit Diagram

Circuit Diagram for Output Characteristic of BJT

 

Output characteristics

1.  Set up the circuit as shown in the diagram.

2.When a base resistor of 1Mohm is connected,base current is set for 4.3 uA (How you find out).   

3. Vary V₂   in steps of 1V and note the corresponding I_C and V_CE

4.Now remove 1M ohm and connect a base resistor of 470K and now the base current is set for 10uA. 

5.Again  vary V₂   in steps of 1V and note the corresponding I_C and V_CE.

6. Plot the output characteristics curve with V_CE on x-axis and I_C on y-axis.

.Result Table

 

IB=10uA, 4.3uA
V2                 Vce	IC
1V
2V
3V
.
.
.
.
.
14V
15V

Expected Graph  Output characteristics