Design And Construction Of A 150W Power Amplifier

ABSTRACT

This work is titled the design and construction of 150W power amplifier. Audio power 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. Audio power amplifier amplifies low-power audio signals (signals composed primarily of frequencies between 20Hz – 20kHz, 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 device is designed to deliver appreciable 150w power to the load. Audio Power amplifiers may be called upon to supply power ranging from a few watts in an audio amplifier to many thousands of watts to a load (speaker). In audio amplifiers the load is usually the dynamic impedance presented to the amplifier by a loudspeaker, and the function is to maximize the power delivered to the load over a wide range of frequencies.

TABLE OF CONTENTS

Title Page

Approval Page

Dedication

Acknowledgement

Abstract

Table of Content

CHAPTER ONE

1.0     Introduction

1.1     background of the study

1.2     Problem statement

1.3     Objective of the project

1.4     Application of the project

1.5      purpose of the project

1.6          significance of the project

1.7          limitation of the project

1.8          Project organisation

CHAPTER TWO

2.0     Literature review

2.1     Historitical background of an amplifier

2.2     Review of classification of power amplifiers

2.3      Classification according to mode of operation

2.4       Review of transistor biasing

CHAPTER THREE

3.0     Construction

3.1     Block diagram of an audio power amplifier

3.2      Circuit diagram of a 100w amplifier

3.3      Circuit operation

3.4     Circuit description

3.5     Power supply circuit

3.6      Parts list of 100 watt amplifier circuit

3.7      Description of components used

CHAPTER FOUR

RESULT ANALYSIS

4.0     Construction Procedure and Testing

4.1     Casing and Packaging

4.2     Assembling of Sections

4.3     Testing of System Operation

4.4      Cost Analysis

CHAPTER FIVE

5.1     Conclusion

5.2     Recommendation

5.3     References

 

CHAPTER ONE

1.0                                                        INTRODUCTION

1.1                                           BACKGROUND OF THE STUDY

An audio power amplifier is an electronic amplifier that amplifies low-power audio signals (signals composed primarily of frequencies between 20 – 200k Hz, the human range of hearing) to a level suitable for driving loudspeakers. It is the final electronic stage in a typical audio playback chain.

Power Amplifier (also known as a large signal amplifier), is to deliver power to the load, and as we know from above, is the product of the voltage and current applied to the load with the output signal power being greater than the input signal power. In other words, a power amplifier amplifies the power of the input signal which is why these types of amplifier circuits are used in audio amplifier output stages to drive loudspeakers.

The power amplifier works on the basic principle of converting the DC power drawn from the power supply into an AC voltage signal delivered to the load. Although the amplification is high the efficiency of the conversion from the DC power supply input to the AC voltage signal output is usually poor.

The preceding stages in such a chain are low power audio amplifiers which perform tasks like pre-amplification (this is particularly associated with record turntable signals), equalization, tone controls, mixing/effects, or audio sources like record players, CD players, and cassette players. Most audio power amplifiers require these low-level inputs to adhere to line levels.

While the input signal to an audio power amplifier may measure only a few hundred microwatts, its output may be tens or hundreds of watts for a home system or thousands or tens of thousands of watts for a concert sound reinforcement system.

Not all amplifiers are the same and are therefore classified according to their circuit configurations and methods of operation.

There are many forms of electronic circuits classed as amplifiers, from Operational Amplifiers and Small Signal Amplifiers up to Large Signal and Power Amplifiers. The classification of an amplifier depends upon the size of the signal, large or small, its physical configuration and how it processes the input signal, which is the relationship between input signal and current flowing in the load.

1.2                                             OBJECTIVE OF THE PROJECT

The main objective of this work is to design and construct an audio power amplifier that will deliver appreciable 150w power to the load. 150W Audio Power amplifiers may be called upon to supply power ranging from a few watts in an audio amplifier to 150 watts to a load (speaker).

1.3                                 PROBLEM STATEMENT

• Addressing crowd used to be difficult, this lead to shouting on top of our voice which lead to loss of voice.
• Sometimes, we desired to play out little audio devices (such as cell phone, DVD, TV, etc) in a way that it can be heard by people from a distance.

In other to bring solution to this problem, an amplifier is used to amplifier small audio signal to a level it can be heard from a distance. An audio amplifier is one kind of electronic device, used to increase the amplitude of audio signals that permit it. This type of amplifier increases low-power audio signals to a level which is apt for making loudspeakers.

1.4                                         APPLICATION OF THE PROJECT

Important applications include public address systems, theatrical and concert sound reinforcement systems, and domestic systems such as a stereo or home-theatre system. Instrument amplifiers including guitar amplifiers and electric keyboard amplifiers also use audio power amplifiers. In some cases, the power amplifier for an instrument is integrated into a single amplifier “head” which contains a preamplifier, tone controls, and electronic effects. In other cases, musicians may create a setup with separate rack mount preamplifiers, equalizers, and a power amplifier in a separate chassis.

1.5                                              PURPOSE OF THE PROJECT

Amplifier’s main purpose is to take the weak signal and make it strong to drive a speaker. The power amplifiers usually get necessary amplification energy of input signals from the AC supply. Ideally without distortion an amplifier can deliver signal at the output without distortion.

1.6                                         SIGNIFICANCE OF THE PROJECT

Today there are many categories of amplifiers used for multifarious purposes. In simple terms an amplifier picks up a weak signal and converts it into a strong one. It is widely used in several devices to boost electrical signals. Radios, televisions and telephones are a few examples to point out in this regard. There are innumerable other applications of amplifiers and it is not easy to enumerate all of them. Some of the common types of amplifiers are used in electronic gadgets and audio systems. These are also used in musical instruments and guitars.

1.7                            LIMITATION OF THE PROJECT

• Noise. This device tends to add some random noise to the signals passing through them, hence degrading the SNR (signal to noise ratio). This, in turn, limits the accuracy of any measurement.
• Limited output voltage, current, and power levels. This amplifier cannot output signals above 150w.

1.8                          PROJECT WORK ORGANISATION

The work is organized as follows: chapter one discuses the introductory part of the work,   chapter two presents the literature review of the study,  chapter three describes the methods applied, chapter four discusses the results of the work, chapter five summarizes the research outcomes and the recommendations.