ABSTRACT

        Over the past two decades, many types of audio amplifier design approaches have been tried. Many of these designs have use larger amount of negative feedback to ensure low closed-loop harmonic distortion. The main contributors to this type of distortion are the output devices. Other contributors are drivers or devices preceding the output devices and the high voltage gain stage also referred as the transconductance stage.

      Before analyzing the basic concept of an audio amplifier, lets define an amplifier. An amplifier is an electronic devices that magnifies signal of a sound. A power amplifier is electronic device that accept a small input power and delivers a large output signal that contains essential wave form from features of the signal input. The aim of constructing this audio amplifier is to achieve consistent maximum power delivery into the load with low distortion. This devices is constructed in five stages; the power supply, the rectifier, the input, the amplification and output stages.

CHAPTER ONE

INTRODUCTION

1.0 BACKGROUND OF  STUDY

An audio amplifier is an electronic device used in every sound production system, which serve as a channel drive for the speaker to obtain a good production of sound. Different varieties of sound system benefits from this device such systems are: receivers intercom, microphone, telephone, pick up coils, general audio monitoring etc. under this, its operation principle will also be viewed. However, this work will give an insight on what make up an audio amplifier, its circuit design and layout design. Amplifier problem arise with drift produced by change in temperature or aging of components. Therefore, special techniques must be employed to reduce the undesirable signal in the output to negligible values.

      This project highlights an audio amplifier’s circuit design and its operation principle. Problems and solutions will be reviewed, its mode of maintenance and testing, general precautions and miscellaneous will be presented in th

1.1      STATEMENT OF PROBLEM

Out in the audio amplifiers market, there are thousands of audio amplifiers. Most of these amplifiers produces low power output, even if there is an audio that has a high power output, it’s still has its weakness.

        Audio amplifiers are of the most important building blocks of sound reproduction in the millennium era. With an emphasis on sound quality in the design of an amplifier, most amplifiers are inefficient. For many amplifiers, poor efficiency is not really a problem. However, there are situations where are more efficient amplifier would be extremely beneficial.

        One example is a battery powered amplifier, when batteries powers up electronic equipment, the amount of power saved by the amplifier will almost be proportional to the time allowed between battery charges. Most high power amplifiers in use today are relatively inefficient. The need to use large heat sinks to dispute the wasted power supply results in an extremely heavy unit.

1.2   AIM AND OBJECTIVE OF THE STUDY  

      This project is aimed at the construction of an audio amplifier that will give an output that preserves the waveform of the input signal and hence reduce the distortion.It objectives are:

v To express in simplest term for any electronic engineering student and even non-technicians to understand amplifying design.

v To broaden the scope of study in the production of sound system.

v To let the readers know the basic component use for the construction of an audio amplifier.

1.3 SIGNIFICANCE OF THE STUDY                                    

      The major significance of this project is to construct and design audio amplifier which will be effective in the production of good sound system for the public and private use. Also it will proffer solution to problems encountered with most commonly used amplifier such as humming, noisy outputs, interference, resonance, unfettered and undesired sound signal, heating etc. The finding and recommendations of this research work will obviously help in solving these problems militating against effective performance in an audio amplifier.

1.4   SCOPE OF THE STUDY

The construction and operation of this audio amplifier is to give a reasonable output power of 200walts. The amplifier is designed to operate into the load such as speakers of various electronics set and it is arrange in five [5] stage which include; power supply (transformer),rectification, input , amplification and output stage.

1.5        LIMITATION OF THE STUDY

In construction of this audio amplifier, certain developments militated against its successful completion at the initial stage. These are:

v Due to the erratic supply of power, the researcher had to wake up late at night in order to construct this project since power was only restored at night.

v Some of the component of the original design had to be change due to scarcity in market.

1.6 DEFINITION OF TERMS

        This section defines some of the relevant terms or words used in the project. They are:

AUDIO: - It is a sound or the reproduction of sound.

AMPLIFIER: - An assembly containing one or more values of transistors and associated components such as inductors, capacitors and resistors to design that the signal applied to the input produce an output of a larger signal.

AUDIO AMPLIFIER: It is electronic device in a sound production system, which function as a drive to the speaker for a good sound production output.

BRIDGING: - A crossover socket between track or component pad during soldering.

COMPONENT: These are electronic devices used collectively to achieve a desire aim in the design of the circuit.

TROUBLESHOOTING:-These are symptoms, trace in an equipment due to fault, dirt, burns and excessive vibration.

RESISTOR:-It is a device that gives opposition to flow of current. It has two terminals or leads but no polarity.

CAPACITOR: - It is an electronic component that has the ability to store and discharge electrical charges.

AMPLIFICATION: It is the ratio of output signal to input signal to input signal. In principle, the output signal must be greater than the input signal for amplification to be useful.

DISTORTION:-It occurs when output waveform is not the same as the input waveform. All amplifiers in practice introduce some measure of distortion.

TRANSDUCER: It is an electromechanical device which converts energy from one form to another and the out is an electrical signals.

RECTIFICATION: - It is a process for changing Alternating currents (AC) to Direct Current (DC) by an electronic device rectifier.

TRANSFORMER:- This is a device that transfers energy between two or more circuits through electromagnetic induction.

TRANSCONDUCTANCE: - This is the property of certain electronic components.  It is the ratio of the current variation at the output to the voltage at the input.

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