Transistor Characteristics lab manual

TRANSISTOR CE CHARACTERISTICS

AIM

To study and plot the input & output characteristics of a NPN transistor in CE configuration. Also to find the following parameters.

• Input impedance, r_i
• Output impedance, r_o
• Forward Current gain, β

COMPONENTS REQUIRED

• Transistor          – BC 107/BC 547/ SL 100
• Resistors            – 100Ω
• DC power supply   – 0-5V, 0-30V
• Voltmeter           – 0-1V, 0-30V
• Ammeter            – 0-100µA, 0-100mA
• Miscellaneous    – Breadboard, Connecting wires, etc.

THEORY

In this configuration, input is applied between the base & emitter and the output is taken from collector & emitter. The emitter of the transistor is common to both input & output ports and hence its named as Common Emitter (CE) configuration.Common emitter is most frequently used configuration for amplification because it provides voltage, current & power gains more than unity and it also has moderate values for input & output impedances.

Input Impedance, r_i

It is the ratio of change in base-emitter voltage, (∆V_BE) to the change in base current (∆I_B) at constant output voltage, V_CE ie,

Output Impedance, r_o

It is the ratio of change in collector-emitter voltage, (∆V_CE) to the change in collector current (∆I_C) at constant input current, I_B ie,

Forward Current Gain, β

It is the ratio of change in collector current to the corresponding change in base current, keeping the output voltage, V_CE as a constant ie,

CIRCUIT DIAGRAM

TABULATION

PROCEDURE

Input Characteristics

• Identify the leads of the given NPN transistor and check the transistor using multimeter.
• Setup the circuit as shown in the figure & verify the connections using multimeter.
• Switch ON the power supplies keeping V_BB at minimum position & V_CE at 0V.
• Note down the value of I_B for different values of V_BE by varying V_BB from 0V to 0.8V/0.9V in steps of 0.1V and enter them in the tabular column.
• Repeat the above step for V_CE say 3V & 6V.
• Plot the input characteristics on graph sheet using the data tabulated with V_BE on x-axis & I_B on y-axis.
• Calculate dynamic input resistance value from the graph plotted.

Output Characteristics

• Switch ON the power supplies keeping V_CC at minimum position & I_B at 0µA.
• Note down the value of I_C for different values of V_CE by varying V_CC from 0V to 10V/15V in steps of 0.5V and enter them in the tabular column.
• Repeat the above step for I_B say 60µA, 80µA & 100µA.
• Plot the output characteristics on graph sheet using the data tabulated with V_CE on x-axis & I_C on y-axis.
• Calculate dynamic output resistance & forward current gain from the graph plotted.

EXPECTED GRAPH

CE input & output characteristics

RESULT