Amplifier is a device for increasing the audio power of a signal by use of an external energy source. It is design to meet up with the amplification demand in homes, offices, industries and especially in music industries. Amplifier increases low-power audio signals (signals composed primarily of frequencies between 20 - 20 000 Hz, the human range of hearing) to a level suitable for driving loudspeakers and is the final stage in a typical audio playback chain, While the input signal to an audio amplifier may measure only a few hundred microwatts, its output may be tens, hundreds, or thousands of watts.
This amplifier uses bipolar transistors which is connected in common emitter mode. The common- emitter circuit is the most widely used of junction, transistor amplifiers. As compared with the common- base connection, it has higher input impedance and lower output impedance. Current gain in the common emitter circuit is obtained from the base and the collector circuit currents.

 

 

TABLE OF CONTENTS

 TITLE PAGE

APPROVAL PAGE
DEDICATION
ACKNOWELDGEMENT
ABSTRCT
TABLE OF CONTENT

CHAPTER ONE

• INTRODUCTION
• AIM AND OBJECTIVE OF THE PROJECT
• SIGNIFICANCE OF THE PROJECT
• PROBLEM AND LIMITATION OF THE PROJECT
• PURPOSE OF THE PROJECT
• APPLICATIONS OF THE PROJECT
• DIFFERENCE BETWEEN BIPOLAR JUNCTION TRANSISTORS (BJTS) AND FIELD EFFECT TRANSISTORS (FETS)
• PROJECT ORGANISATION

CHAPTER TWO               

LITERATURE REVIEW
2.0      LITERATURE REVIEW
2.1      OVERVIEW OF BIPOLAR JUNCTION TRANSISTOR
2.2     BJT AMPLIFIER CONFIGURATIONS
2.3     STRUCTURAL REVIEW OF BJT

2.4    TYPES OF BIPOLAR JUNCTION TRANSISTOR

2.5     HISTORICAL BACKGROUND OF BIPOLAR TRANSISTOR
2.5    THEORY AND MODELING
CHAPTER THREE
DESIGN METHODOLOGY
3.1      CIRCUIT DIAGRAM
3.2      COMPONENTS USED
3.3      CRICUIT OPERATION AND DESCRIPTION
3.4      DESCRPTION OF COMPONENT USED

CHAPTER FOUR
RESULT ANALYSIS
4.1 CONSTRUCTION PROCEDURE AND TESTING
4.2 CASING AND PACKAGING
4.3 ASSEMBLING SECTION
4.4 TESTING OF SYSTEM OPERATION
4.5    INSTALLATION OF THE COMPLETED DESIGN
4.6 RESULT ANALYSIS

CHAPTER FIVE

5.0      SUMMARY, RECOMMENDATION AND REFERENCES

• CONCLUSION
• RECOMMMENDATION

5.3     REFERENCES

 

CHAPTER ONE
1.1                                                        INTRODUCTION
In electronics, a common-emitter amplifier is one of three basic single-stage bipolar-junction-transistor (BJT) amplifier topologies, typically used as the voltage amplifier.
BJT refers to Bipolar Junction Transistor. It is a three-terminal electronic device constructed of doped semiconductor material. It is called ‘Bipolar’ because charge is carried by both, electrons and holes. Hence, operation of the device is due to bi poles (or opposite charges). Charge flow in a BJT is due flow of charges flow across a junction between two regions of different charge concentrations.
In a BJT circuit, the base terminal of the transistor serves as the input, the collector is the output, and the emitter is common to both (for example, it may be tied to ground reference or a power supply rail), hence its name.

1.2                                   AIM AND OBJECTIVE OF THE PROJECT
The aim of this work is to design an amplifier using bipolar transistor in a common emitter (ce) configuration.
At the end of this work, the student involved will be able to:

• Understand the operation of bipolar junction transistor.
• Know the pin-out and pin functions of the bipolar junction transistor
• Design an amplifier circuit,
• Know the difference between bipolar transistor and field effect transistor etc.

1.3                                         SIGNIFICANCE OF THE PROJECT
The following are the advantages of BJT amplifier:

• There is high current density.
•  It operates in medium to high Voltage range.
•  There is low forward voltage drop.

1.4                           PROBLEMS AND LIMITATION OF THE PROJECT
However, the following are some of the problems of the project-

• It has a very complex base control. Hence, it may lead to confusion and hence, requires skilful handling.
• The switching time is not very fast compared to the high alternating frequency of voltage and current source.

1.5                                              PURPOSE OF THE PROJECT
The common emitter amplifier is one of the simplest and elementary transistor amplifier that can be made. The main purpose of this circuit is pre-amplification i.e it makes weak signals strong enough for further processing or amplification.

1.6                   APPLICATIONS OF THE PROJECT

Low-frequency voltage amplifier

The input capacitor C removes any constant component of the input, and the resistors R1 and R2 bias the transistor so that it will remain in active mode for the entire range of the input. The output is an inverted copy of the AC component of the input that has been amplified by the ratio RC/RE and shifted by an amount determined by all four resistors. Because RC is often large, the output impedance of this circuit can be prohibitively high. To alleviate this problem, RC is kept as low as possible and the amplifier is followed by a voltage buffer like an emitter follower.

Radio

Common-emitter amplifiers are also used in radio frequency circuits, for example to amplify faint signals received by an antenna. In this case it is common to replace the load resistor with a tuned circuit. This may be done to limit the bandwidth to a narrow band centered around the intended operating frequency. More importantly it also allows the circuit to operate at higher frequencies as the tuned circuit can be used to resonate any inter-electrode and stray capacitances, which normally limit the frequency response. Common emitters are also commonly used as low-noise amplifiers.

1.7    DIFFERENCE BETWEEN BIPOLAR JUNCTION TRANSISTORS (BJTS) AND FIELD EFFECT TRANSISTORS (FETS)
Below table is the difference between bipolar junction transistors (BJTs) and field effect transistors (FETs).

BJTs vs FETs
How it operates	BJTs	FETs
	BJTs are current-controlled. They require a biasing current to the base terminal of operation.	FETs are voltage-controlled. They only require voltage applied to the gate to turn the FET either on or off. They do not require a biasing current for operation.
Input Impedance	BJTs offer smaller input impedances, meaning they draw more current from the power circuit feeding it, which can cause loading of the circuit.	FETs offer greater input impedance than BJTs. This means that they practically draw no current and therefore load down the power circuit that's feeding a lot less and minimimally.
Gain (Transconductance)	BJTs offer greater gain at the output than FETs.	The gain (or transconductance) of FETs are smaller than for BJTs.
Size	BJTs are larger in size and therefore take up more physical space than  FETs normally.	FETs can be manufactured much smaller than BJTs. This is especially important for integrated circuits that are composed up of many transistors.
Popularity	BJTs are less popular and less widely used	FETS are definitely more popular and widely used in commercial circuits today than BJTs
Cost	BJTs are cheaper to manufacture	FETs, especially MOSFETs, are more expensive to manufacture

1.7                          PROJECT WORK ORGANISATION
The various stages involved in the development of this project have been properly put into five chapters to enhance comprehensive and concise reading. In this project thesis, the project is organized sequentially as follows:
Chapter one of this work is on the introduction to the study. In this chapter, the background, significance, objective limitation and problem of the study were discussed.
Chapter two is on literature review of the study. In this chapter, all the literature pertaining to this work was reviewed.
Chapter three is on design methodology. In this chapter all the method involved during the design and construction were discussed.
Chapter four is on testing analysis. All testing that result accurate functionality was analyzed.
Chapter five is on conclusion, recommendation and references.

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