Design And Construction Of 50Watts Audio Amplifier

Project and Seminar Material For Electrical Electronics Engineering EEE

Project and Seminar Material For Electrical Electronics Engineering EEE


This abstract on the project report of Design and Construction of 50watts audio amplifier consist of four chapters.

Chapter one introduces the entire project and its overview generally with the general block diagram of feedback amplifier while

Chapter two contains the literature review, which is a brief history of the project and its modifications overtime till this present day audio amplifier.

Chapter three has the main stream of the project. It contains the circuit and components analysis, theory of design, circuit diagrams of the entire section, and block diagram of this very project, principle of operation of our project, precautions and problems encountered.

The chapter four of this report contains the conclusion and recommendations of this project.

Table Of Contents

Preliminary Page(s)

  • Title
  • Declaration
  • Approval
  • Dedication
  • Acknowledgement
  • Abstract
  • Table of Content

Chapter One

1.0 Introduction

Chapter Two

2.0 Literature Review

Chapter Three

3.0 Design And Construction Of 50Watts Audio Amplifier

    • Components and Circuit Analysis
  • 3.1 Theory Design
    • The circuit principal components.
    • Principles of Operation
    • Circuit Diagrams
    • Block Diagrams
    • Precautions
    • Problems Encountered

Chapter Four

4.0 Conclusion and Recommendation

  • References

Chapter One

1.0 Introduction

By definition audio amplifier is an electronic device that amplifies low-power audio signal (signals composed primarily of frequencies between 20 and 20 kHz) to a level suitable of driving loudspeakers and in the final stage in a typical audio playback chain.

The preceding stages in such a chain are low power audio amplifiers which perform task like pre-amplification equalization, tone control and mixing effects.

While the input to audio amplifier may measure only a few hundred microwatts, its output may be tens, hundred or thousand of watts.

In the sphere of electrical electronics engineering, the main quantities of electricity voltage and current are manipulated for signal control. When a particular circuit is designed to electronically manage the flow of current within a potential difference (voltage) the final signal of its physical quantity called an audio signal could be generated. The generated signal could be in the form of noise as a result of electrons and holes drift.

Though the audio signal initially carries no intelligence. To impress intelligence on the audio signal, some electronic elements are electronically arranged in their aggregate function mode and desire. This connectivity is a well electrically analyzed scheme as contained in this report.

The design and construction of the audio signal amplifier attracts a correctly arranged circuit for this purpose.
Moreover, the need for amplification implies, some electric signal when introduced in the circuit develops attenuation varying below certain marginal utility level. The amplifier is developed to boost and compensate signal to a level of usefulness with induced modification of the output signal.

The Audio Amplifier has Three Circuits:

I) The Power Source:

This circuit rectifies and filters a.c signal to d.c signal and delivers it to the second circuit.

Ii) Pre-Amplification Circuit:

This circuit pre-amplifies the input signal to an appreciable level and then be fed to the main amplification circuit.

Iii) The Main Amplification Circuit:

This circuit amplifies the output of the pre-amplifier as its input, to a level based on the design, to drive the load (loudspeaker)

For better introduction of this project it necessary to look at the basic block diagram of a feedback amplifier.

Block diagram of basic amplifier with feedback network.

Block diagram of basic amplifier with feedback network.

Significance Of The Blocks.

Signal Source:

This is the signal generator which in this project is an audio CD player machine.
MIXER: This section synchronizes the input source and the feedback signal.

Amplifying Network:

This section amplifies the signal to the appreciable extend as determined by its characteristics on design.

Feedback Network:

This section is used to feed the mixer with a sample of the output meant to control the input and also to introduce stability into the system.

Sampling Network:

This section is responsible for feeding the feedback network with a sample of the output.
Principally, amplifiers make use of components such as transistors for its mode operation in different configurations. But this project uses common emitter.

General Classification Of Amplifiers

There are various ways of classifying amplifiers; it could be according to their mode operation based on some pre-determined set of values.

Based on input we have:

  • Small signal amplifier
  • Large signal amplifier

Based on output we have:

  • Voltage amplifier
  • Power amplifier

Based on the frequency response we have

  • Audio frequency (AF),
  • Intermediate frequency (IF) and
  • Radio frequency (RF) amplifiers

Based on the biasing condition we have:

  • Class A,
  • Class AB,
  • Class B and
  • Class C amplifiers.

In the recent past and nowadays, the construction and design of amplifiers are achieved by the use of audio power amplifier I.C.

The use of audio power I.C, which mostly comes as op-amp I.C makes the design of an amplifier circuit easier and less cumbersome. The performance of this I.C’s are rated high with regard to output fidelity, because they have in them well inbuilt and well biased transistors as its op-amp with very high sensitivity to voltage signal.

Chapter Four

4.0 Conclusion And Recommendation


The design and construction of an audio amplifier can be achieved in several ways by many circuit elements combination, all tending to amplify sound to an appreciable level.

In this project, we used the circuit elements that were described above for simplicity of design and ease of operation. As a final yeare project, the adopted circuit is very simply to design construct and also explain in detail because it cut across almost all other design components.

With every necessary precaution on usage the amplifier is highly reliable. Also during the cause of this project, the importance of maintainability was highly considered to make the amplifier fit for Nigerian homes and school labouratories.


For the efficient use of this equipment and necessarily for design modification, we hereby make recommendations to assist the user or the modifier.

As most of the circuit elements are susceptible to heat, we recommend that a well ventilated environment be made available to the student carrying out such project. And also for some advanced electronic tools be made available, because scarcity of tools also delay the time of completion of this project. We also urge the school to continue with their sound laying of the theoretical and practical knowledge of electronics at all levels as it helped us tremendously in making this project a success.

Design And Construction Of 50Watts Audio Amplifier

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