Design And Construction Of A 50W Power Amplifier

This work is titled the design and construction of 50W power amplifier. 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. A 50W power amplifier amplifies 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 device is designed to deliver appreciable 50w 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 hundreds or 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.

A 50w amplifier can be sued to amplify the sound of audio sound system like mini radio cassette player, compact disc player, turn table record player, car radio cassette player or any other sound system that requires increased audio.

This amplifier when produced in large or commercial quality, according to purpose will create job opportunity, provide indigenous electronics technology industry, and it will contribute to economic growth of the nation.

TABLE OF CONTENTS

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

TABLE OF CONTENT

CHAPTER ONE

• INTRODUCTION
  • BACKGROUND OF THE PROJECT
  • PROBLEM STATEMENT
  • AIM OF THE PROJECT
  • OBJECTIVE OF THE PROJECT
  • APPLICATION OF THE PROJECT
  • PURPOSE OF THE PROJECT
  • SIGNIFICANCE OF THE PROJECT
  • LIMITATION OF THE PROJECT
  • RESEARCH QUESTION
  • 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 500W AMPLIFIER

3.3     CIRCUIT OPERATION

3.4     CIRCUIT DESCRIPTION

3.5     POWER SUPPLY CIRCUIT

3.6     PARTS LIST OF 50WATT 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

5.2      REFERENCES

CHAPTER ONE

• INTRODUCTION

1.1                                         BACKGROUND OF THE PROJECT

An audio amplifier is an electronic amplifier that amplifies 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. It is the final electronic stage in a typical audio playback chain.

An audio 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, an audio 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.

An audio 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 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. In “Electronics”, small signal amplifiers are commonly used devices as they have the ability to amplify a relatively small input signal, for example from a Sensor such as a photo-device, into a much larger output signal to drive a relay, lamp or loudspeaker for example.

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.

• STATEMENT OF THE PROBLEM

• 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.

1.3                                                   AIM OF THE PROJECT

The aim of this work is to build an electronic device that amplifies low-power electronic audio signals such as the signal from radio receiver or electric guitar pickup to a level that is high enough for driving loudspeakers

1.4                                             OBJECTIVE OF THE PROJECT

The main objective of this work is to design and construct an audio amplifier that will deliver appreciable 50w power to the load. A 50w Audio amplifiers may be called upon to supply power ranging from a few watts in an audio amplifier to 50 watts to a load (speaker).

1.5                                         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.

1.6                                              PURPOSE OF THE PROJECT

Amplifier’s main purpose is to take the weak signal and make it strong to drive a speaker. An audio amplifier 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.

1.7                                         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.

1.8                                          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. This amplifier can be used to amplify audio signals from laptop speakers, portable speakers

1.9                                           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 produce more than 50w.

1.9                                                   RESEARCH QUESTION

1. What is the purpose of an amplifier in a sound system?
2. What is the function of a power amplifier?

iii. What are the applications of power amplifier?

1. Why do we need power amplifiers?
2. What is the use of amplifier?
3. Why do you need an amplifier for speakers?

vii. How does audio amplifier work?

1.10                                      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 50w audio amplifier. In this chapter, the background, significance, objective limitation and problem of 50w audio amplifier were discussed.

Chapter two is on literature review of a 50w audio amplifier. 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.

CHAPTER TWO

2.0                                                    LITERATURE REVIEW

2.1                         HISTORITICAL BACKGROUND OF AN AMPLIFIER

The audio amplifier was invented in 1909 by Lee De Forest when he invented the triode vacuum tube. The triode was a three terminal device with a control grid that can modulate the flow of electrons from the filament to the plate. The triode vacuum amplifier was used to make the first AM radio…