Description
ABSTRACT
This work is titled the design and construction of 5W 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 5W 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 5w 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 5w 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 5W 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 5w power to the load. A 5w Audio amplifiers may be called upon to supply power ranging from a few watts in an audio amplifier to 5watts 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 5w.
1.9 RESEARCH QUESTION
- What is the purpose of an amplifier in a sound system?
- What is the function of a power amplifier?
iii. What are the applications of power amplifier?
- Why do we need power amplifiers?
- What is the use of amplifier?
- 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 5w audio amplifier. In this chapter, the background, significance, objective limitation and problem of 5w audio amplifier were discussed.
Chapter two is on literature review of a 5w 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 FIVE
5.1 SUMMARY
Amplifiers are used extensively in electronic circuits to make an electronic signal bigger without affecting it in any other way. Generally we think of Amplifiers as audio amplifiers in the radios, CD players and stereo’s we use around the home. In this amplifier tutorial section we looked at the amplifier which is based on a single bipolar transistor as shown below, but there are several different kinds of transistor amplifier circuits that we could use.
Small Signal Amplifiers are also known as Voltage Amplifiers.
- Voltage Amplifiers have 3 main properties, Input Resistance, Output Resistance and Gain.
- The Gain of a small signal amplifier is the amount by which the amplifier “Amplifies” the input signal.
- Gain is a ratio of input divided by output, therefore it has no units but is given the symbol (A) with the most common types of transistor gain being, Voltage Gain (Av), Current Gain (Ai) and Power Gain (Ap)
- The power Gain of the amplifier can also be expressed in Decibels or simply dB.
- In order to amplify all of the input signal distortion free in a Class A type amplifier, DC Base Biasing is required.
- DC Bias sets the Q-point of the amplifier half way along the load line.
- This DC Base biasing means that the amplifier consumes power even if there is no input signal present.
- The transistor amplifier is non-linear and an incorrect bias setting will produce large amounts of distortion to the output waveform.
- Too large an input signal will produce large amounts of distortion due to clipping, which is also a form of amplitude distortion.
- Incorrect positioning of the Q-point on the load line will produce either Saturation Clipping or Cut-off Clipping.
- The Common Emitter Amplifier configuration is the most common form of all the general purpose voltage amplifier circuit using a Bipolar Junction Transistor.
- The Common Source Amplifier configuration is the most common form
of all the general purpose voltage amplifier circuit using a Junction Field Effect Transistor.
- Large Signal Amplifiers are also known as Power Amplifiers.
- Power Amplifiers can be sub-divided into different Classes, for example:
- Class A Amplifiers– where the output device conducts for all of the input cycle.
- Class B Amplifiers– where the output device conducts for only 50% of the input cycle.
- Class AB Amplifiers– where the output device conducts for more than 50% but less than 100% of the input cycle.
- An ideal Power Amplifier would deliver 100% of the available DC power to the load.
- Class A amplifiers are the most common form of power amplifier but only have an efficiency rating of less than 40%.
- Class B amplifiers are more efficient than Class A amplifiers at around 70% but produce high amounts of distortion.
- Class B amplifiers consume very little power when there is no input signal present.
- By using the “Push-pull” output stage configuration, distortion can be greatly reduced.
- However, simple push-pull Class B Power amplifiers can produce high levels of Crossover Distortion due to their cut-off point biasing.
- Pre-biasing resistors or diodes will help eliminate this crossover distortion.
- Class B Power Amplifiers can be made using Transformers or Complementary Transistors in its output stage.
