American International University- Bangladesh (AIUB)

Faculty of Engineering (FE)

ELECTRONIC DEVICES LAB

Course Name : Course Code : EEE 2104
Spring -2023-2024
Semester : Sec : J
MD. ALOMGIR KABIR
Lab Instructor : Group: 3

Experiment No : 05
Experiment Name : Study of Transistor Characteristics in Common Emitter Amplifier

Submitted by (NAME): Student ID:

Group Members ID Name

1. Istiaque Mahbub Isti 22-49167-3
2. Eshika Rani Pall 22-49200-3
3. Khadija Akter 22-48295-3
Ibrahim Khalil Ullah
4. 22-48301-3
Midul
5. Wasif Asad Alvi 22-46451-1

Performance Date : 20/02/24 Due Date : 27/02/2024

Marking Rubrics (to be filled by Lab Instructor)

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(Out of ):
Title: Study of Transistor Characteristics in Common Emitter Amplifier
Abstract:
The main objective of this experiment is to be familiarized with the bipolar junction transistors, also known
as BJTs. In this experiment, we study the biasing of a Common Emitter Amplifier and obtain the input and
output characteristics of a common emitter based BJT circuit.

Aim Of Objective:
1.Learned the BJT Input (VBE vs IB) and Output (VCE vs IC) curve.
2.Learned how the VCE is affecting the input curve & IB is affecting the output curve.
3.Learned how to design a BJT small signal analysis circuit.

Introduction:
BJT stands for Bipolar Junction Transistor. It is a type of transistor that
uses both electron and hole charge carriers. There are two types of BJT:
NPN (Negative-Positive-Negative) and PNP (Positive-Negative-Positive).
The basic structure of a BJT includes three semiconductor regions: the
emitter, base, and collector. The flow of electric charge in a BJT is
controlled by the voltage applied to the base terminal. When a small
current flows into the base, it allows a larger current to flow between
the collector and emitter terminals. This amplification property makes
BJT a key component in electronic circuits, including amplifiers,
oscillators, and digital switches.
BJTs have some advantages, such as high current gain and fast switching
speeds, but they also have limitations, including sensitivity to
temperature variations and a higher power consumption compared to
other types of transistors, like MOSFETs (Metal-Oxide-Semiconductor
Field-Effect Transistors).
Device structure of bipolar junction transistors
A BJT can be thought of as two diodes connected opposite to each other in series. There can be two types
of BJT in terms of junctions. They are the NPN and PNP transistors. The base (B) of the transistor is formed
by the central region in both instances, while the collector (C) and emitter (E) are formed by the exterior
regions. Through metal contacts, such as aluminum, external wire connections are established to the p
and n regions, the transistor terminals.
Figure 1: Type of BJTS
Figure 1 shows a cross section of the two types of BJTs, which include an emitter-base junction and a
collector-base junction. Bipolar transistors, such as NPN or PNP transistors, are named such because both
electrons and holes, the two types of carriers, contribute to the total current. Either the electronics or the
holes control the current flow in a field effect transistor. A field effect transistor is a unipolar device as a
result. The geometry of the device, such as the width of the base area, and the doping concentrations in
each of the device's separate regions determine the current and voltage amplification of a BJT. The doping
concentration in the emitter area is often greater than that in the base region in order to obtain a high
current amplification. Between the emitter and the collector, there is a thin, weakly doped layer called the
base that regulates the flow of charge carriers.

Circuit Configuration:
The NPN and PNP transistor symbols are seen in figure 2. Whether a BJT is an NPN or a PNP transistor is
always denoted by an arrow on the transistor's emitter.

Figure 2: BJT symbols and configuration

A BJT can be set up in one of three different ways. Each time, the input and output circuits seen in figure 2
share a terminal.

The common emitter arrangement, which is the most used configuration for transistor amplifiers, is
utilized for voltage and current amplification.

A popular collector design that is frequently referred to as an emitter follower since its output is derived
from the emitter resistor Because of how much greater its input impedance is than its output impedance,
it may be used as an impedance matching device.
Because the base partitions the input and output, it minimizes oscillations at high frequencies, which is
why the common base arrangement is utilized for high frequency applications. In comparison to the
common collector, it has a high voltage gain, a low input impedance, and a high output impedance.

Biasing of Bipolar Junction Transistors:

The BJT is often employed as an amplifier or switch. The transistor needs to be appropriately biased in
order for it to carry out these tasks. Different modes of operation for the BJT are obtained depending on
the bias state, forward or reverse bias, of each BJT junction. These are the three modes' definitions:

• Active: The collector junction is reverse biased while the emitter junction is forward biased. The BJT
may be used as an amplifier and operates in the active mode.

• Saturation: The connections at the emitter and collector are both forward biased. The saturation
mode corresponds to the on state of the BJT if it is being used as a switch.

• Cut-off: The junctions of the emitter and collector are both reverse biased. When employed as a
switch, the BJT's off state corresponds to the cut-off mode.

Input and Output Characteristics:

The input characteristic curves can be plotted between IB and VBE while maintaining a constant VCE
voltage. The input characteristics resemble those of a diode that is forward biased. Only a small variation
in base-to-emitter voltage is seen. The ratio of the tiny change in base-to-emitter voltage to the little
change in base current is used to calculate the input dynamic resistance.

Figure 3: BJT Common Emitter Input Characteristics

By maintaining a constant base current (IB), output characteristic curves are drawn between the collector
current (IC) and the collector-to-emitter voltage drop. Nearly horizontal curves may be seen here. Again,
the output dynamic resistance may be determined by dividing the minor variation in the emitter-to-
collector voltage drop by the small variation in collector current.
Figure 4: BJT Common Emitter Output Characteristics

Components:

1) Trainer Board

2) Transistor

3) Resistors

4) DC Power Supply

5) Power Supply

6) Multimeter

Circuit Pictures:
Figure: Common Emitter BJT Circuit

Simulation:

Simulation of The Transistor circuit in CE configuration (RB= 9.9kΩ, RC= 1kΩ, IB=100µA, VBB=0V, VCC=8V)

Simulation of The Transistor circuit in CE configuration (RB= 9.9kΩ, RC= 1kΩ, IB=100µA, VBB=0.5V, VCC=8V)
Simulation of The Transistor circuit in CE configuration (RB= 9.9kΩ, RC= 1kΩ, IB=100µA, VBB=1V, VCC=8V)

Simulation of The Transistor circuit in CE configuration (RB= 9.9kΩ, RC= 1kΩ, IB=100µA, VBB=1.5V, VCC=8V)
Simulation of The Transistor circuit in CE configuration (RB= 9.9kΩ, RC= 1kΩ, IB=100µA, VBB=2V, VCC=8V)

Simulation of The Transistor circuit in CE configuration (RB= 9.9kΩ, RC= 1kΩ, IB=100µA, VBB=2.5V, VCC=8V)

Simulation of The Transistor circuit in CE configuration (RB= 9.9kΩ, RC= 1kΩ, IB=100µA, VBB=0V, VCC=16V)
Simulation of The Transistor circuit in CE configuration (RB= 9.9kΩ, RC= 1kΩ, IB=100µA, VBB=0.5V,
VCC=16V)

Simulation of The Transistor circuit in CE configuration (RB= 9.9kΩ, RC= 1kΩ, IB=100µA, VBB=1V, VCC=16V)

Simulation of The Transistor circuit in CE configuration (RB= 9.9kΩ, RC= 1kΩ, IB=100µA, VBB=1.5V,
VCC=16V)
Simulation of The Transistor circuit in CE configuration (RB= 9.9kΩ, RC= 1kΩ, IB=100µA, VBB=2V, VCC=16V)

Simulation of The Transistor circuit in CE configuration (RB= 9.9kΩ, RC= 1kΩ, IB=100µA, VBB=2.5V,
VCC=16V)

Simulation of The Transistor circuit in CE configuration (RB= 10kΩ, RC= 1kΩ, IB=0µA, VBB=0V, VCC=0V)
Simulation of The Transistor circuit in CE configuration (RB= 10kΩ, RC= 1kΩ, IB=0µA, VBB=0V, VCC=4V)

Simulation of The Transistor circuit in CE configuration (RB= 10kΩ, RC= 1kΩ, IB=0µA, VBB=0V, VCC=8V)

Simulation of The Transistor circuit in CE configuration (RB= 10kΩ, RC= 1kΩ, IB=0µA, VBB=0V, VCC=12V)
Simulation of The Transistor circuit in CE configuration (RB= 10kΩ, RC= 1kΩ, IB=0µA, VBB=0V, VCC=16V)

Simulation of The Transistor circuit in CE configuration (RB= 10kΩ, RC= 1kΩ, IB=50µA, VBB=1.07V, VCC=0V)

Simulation of The Transistor circuit in CE configuration (RB= 10kΩ, RC= 1kΩ, IB=50µA, VBB=1.07V, VCC=4V)

Simulation of The Transistor circuit in CE configuration (RB= 10kΩ, RC= 1kΩ, IB=50µA, VBB=1.07V, VCC=4V)
Simulation of The Transistor circuit in CE configuration (RB= 10kΩ, RC= 1kΩ, IB=50µA, VBB=1.07V,
VCC=12V)

Simulation of The Transistor circuit in CE configuration (RB= 10kΩ, RC= 1kΩ, IB=50µA, VBB=1.07V,
VCC=16V)

Simulation of The Transistor circuit in CE configuration (RB= 10kΩ, RC= 1kΩ, IB=100µA, VBB=1.586V,
VCC=0V)

Simulation of The Transistor circuit in CE configuration (RB= 10kΩ, RC= 1kΩ, IB=100µA, VBB=1.586V,
VCC=4V)
Simulation of The Transistor circuit in CE configuration (RB= 10kΩ, RC= 1kΩ, IB=100µA, VBB=1.586V,
VCC=8V)

Simulation of The Transistor circuit in CE configuration (RB= 10kΩ, RC= 1kΩ, IB=100µA, VBB=1.586V,
VCC=12V)

Simulation of The Transistor circuit in CE configuration (RB= 10kΩ, RC= 1kΩ, IB=100µA, VBB=1.586V,
VCC=16V)

Data Table:
Input Characteristics

VCC = 8V VCC = 16V

VBB VBE IB (mA) VBB VBE IB(mA)
0v 103.4mV 0 0v 0V 0 mA
0.5v 0.567V 0 0.5v 0.578V 0 mA
1v 0.729V 0.02mA 1v 0.718V 0.03mA
 1.5v 0.762V 0.07mA 1.5v 0.746V 0.07mA
2v 0.779V 0.12mA 2v 0.745V 0.12mA
2.5v 0.788V 0.17mA 2.5v 0.785V 0.17mA

Output Characteristics

IB = 0μA IB = 50μA IB = 100μA

Vcc (V) VCE IC (mA) Vcc (V) VCE IC (mA) Vcc (V) VCE IC (mA)
0v 0V 0 0v 27.7mV 0 0v 19.6mV 0
4v 4 0 4v 340mV 3.71mA 4v 141.8mV 4.05mA
8v 8 0 8v 4.11V 4.18mA 8v 0.663V 7.43mA
12v 12 0 12v 7.91V 4.30mA 12v 4.25V 7.81mA
16v 16 0 16v 11.78V 4.38mA 16v 7.85V 8.18mA

Graph:

IB vs VBE graph of Input Characteristics (VCC = 8V)

IB vs VBE graph of Input Characteristics (VCC = 16V)

When IB = 0μA

When IB = 50μA
When IB = 100μA

Result and Discussion:

We are taking all the measurement in the trainer board and in the simulation, it can be seen that the
measured values from the experimental circuits and the simulation values are almost identical. I B vs VBE
graph of Input Characteristics (VCC = 8V), IB vs VBE graph of Input Characteristics are(VCC = 16V) graph from
the experimental values can be considered identical if the unavoidable human is neglected.
From input and output characteristics the Transistor Characteristics in Common Emitter Amplifier can be
noticed. A small amount of current and voltage of the input is getting amplified in the output.

References:
1. Robert L. Boyleston, Louis Natinsky, Electronic Devices and Circuit Theory, Ninth Edition, 2007-
2008
2. Adel S. Sidra, Kenneth C. Smith, Microelectronic Circuits, Saunders College Publishing, 3rd ed.,
ISBN: 0-03-051648-X, 1991.
3. American International University–Bangladesh (AIUB) Electronic Devices Lab Manual.
4. David J. Comer, Donald T. Comer, Fundamentals of Electronic Circuit Design, john Wiley & Sons
Canada, Ltd.; ISBN: 0471410160, 2002.