Introduction: Amplifier device that accepts a varying input signal and produces an output signal that varies in the same way as the input but has larger amplitude. The input signal may be a current, a voltage, a mechanical motion, or any other signal; the output signal is usually of the same nature. The most common types of amplifiers are electronic and have transistors or electron tubes as their principal components. Electronic amplifiers are used in radio and television transmitters and receivers, audio and stereo systems, intercoms, and other consumer electronics devices. Amplifiers in their simplest form are built around a single transistor. In one type of single-transistor amplifier, known as a common-emitter circuit, a varying input voltage is fed to the base of the transistor, and the output appears at the transistor’s collector; the ratio of the output voltage to the input voltage is called the voltage gain. For many purposes a single transistor does not provide sufficient gain, or amplification.
In a cascade, or multistage, amplifier, the output of the first amplifying device (transistor) is fed as input to the second amplifying device, whose output is fed as input to the third, and so on until an adequate signal amplification has been achieved. In a device such as a radio receiver, several amplifiers boost a weak input signal until it is powerful enough to drive a speaker. Usually, multistage amplifiers are not made of discrete components, but are built as integrated circuits . Another less common group of electronic amplifiers use magnetic devices as their principal components. There are also many kinds of mechanical amplifiers, e.g., the power steering This audio amplifier project is a class AB audio power amplifier using a TDA2003 module power amplifier. It is easy to construct and has only a few external components. The module is designed with short circuit and thermal protection. It can drive loads as low as 1.6 ohm and is capable of delivering over 10 watts from a 16 V DC power supply.
The power supply required for is 8 – 18V DC at 1 Amp or more. Maximum output power will only be obtained with a power supply of greater than 1A at 16V DC, and using 2 ohm speakers (or 2 by 4 ohm speakers in parallel). However approximately 4W RMS can be obtained with a 12V DC, 1A supply into a 4 ohm load. The power supply should be well filtered to reduce mains hum, the on board capacitors alone are not adequate for this purpose but are necessary to ensure stability. Extra filtering is unnecessary if operating from a battery. If two boards are used for stereo, you will need to double the size of the power supply.
Circuit Diagram
10 W Audio Amplifiers Circuit diagram
Step Taken While Preparing Circuit:
The main purpose of printed circuit is in the routing of electric currents and signals through thin copper layer that is bounded firmly to and insulating base material some times called the substrata. This base is manufactured with an integral bounded layer of thin copper foil which has to be partly etched or other wise removed to arrive at a pre-designed pattern to suite the circuit connections.
From the constructors point of view the main attraction of using PCB is its role as the mechanical support for small components. There is less need for complicated and time consuming metal work or chassis construction except perhaps in providing the [mal enclosure. Most straight forward circuit designs can be easily converted into printed wiring layout the thorough required to carry out the conversion can often highlights any possible error that would otherwise be missed in convention point to point wiring. The finished project is usually neater and truly a work of art. Through proper design of PCB can get noise immunity. The fabrication process of the printed circuit board will determine to a large extent the price and reliability of the equipment. A common target aimed at is the fabrication of small series of highly reliable professional quality PCBs with low investment cost.
There are two types of PCB:-
- Single sided board
- Double sided board
Single sided board: The single sided PCBs are mostly used in endearment electronics where manufacturing costs have to be kept at a minimum however in industrial electronics. Also cast factors cannot be neglected and single sided boards should be used whenever a particular circuit can be accommodated on such boards.
Double sided boards: Double sided PCBs can be made with or without plated through holes. The production of boards with plated-through holes is fairly expensive. Therefore, plated through hole boards are only chosen where the circuit complexity and density dose not leave any other choice.
Layout Design:
The layout of a PCB has to incorporate all the information on the board before one can go on to the artwork preparation. This means that a concept, which clearly defines all the details of the circuit, is a prerequisite before the actual layout can start. The detailed circuit diagram is varying important for the layout designer but the must also be familiar with the design concept and with the philosophy behind the equipment. When designing the layout one should observe the minimum size (component body length and weight). Before starting to design the layout have all the required components to hand so that an accurate assessment of space can be made care must be taken so as to allow for adequate air flow after the components have been mounted. It might be necessary to turn some components round to a different angular position so that terminals are closer to the connections of other components. The scale can be checked by positioning the components on the squad paper. If any connection crosses, then one can reroute to avoid such condition. All common or earth lines should ideally be connected to a common line routed around the perimeter of the layout this will act as the ground plane. If possibly try to route the outer supply line ground plane. If possibly try to route the other supply lines around the apposite edge of the layout or through the center. The first step is to rearrange the circuit to eliminate the crossover without altering the circuit detail in any way.
Plan the layout as if looking at the top side of the board first this should be translated in reverse later for the etching pattern. Larger areas are recommended to maintain good copper adhesive. It is important to bear in mind always that copper track width must be at least to the recommended minimum dimensions and allowance must be made for increased width where termination holes are needed from this aspect it can become little tricky to negotiate the route for connections to small transistors. One can effect the copper interconnection pattern in the under side of the board in a way described below Make the interconnections pattern looking like conventional point to point writing by routing uniform width of copper from component to component.
Etching Process: Etching process requires the use of chemicals, acid resistant dishes and a running water supply. Ferric chloride is the maximum used solution, but other enchants such as ammonium sulfate can be used.
Nitric acid can also be used but in general it is not used due to the poisonous fumes. The pattern prepared is glued to the copper surface of the board using a latex type of adhesive that can be cubed after use. The pattern is laid firmly on the copper, use vary sharp knife to cut round the pattern carefully and remove the paper corresponding to the required copper pattern areas. Then apply the resist solution clean outlines as for as possible. While the board is drying to test all components. Before going to the next stage, check the whole pattern and cross check against the circuit diagram check for any foreign matter on the copper. The etching bath should be in a glass or enamel disk. If using crystal of ferric chloride these should be thoroughly dissolved in water to the proportion suggested. There should be 0.5 Lt. Of water for 125 gm of crystal. The board is then immersed in FeCl3 solution for 12 hours, in this process only the non hidden copper portion is etched out by the solution.
2FeCl3 + 2H2O + 3Cu 0 3CuCl2 + 2Fe (OH) 2
Waste liquid should be thoroughly diluted and buried in water land never pour down the drain. To prevent particles of copper hindering further etching, agitate the solutions carefully by gently twisting or rocking the tray. The board should not be left in the bath a moment longer than is needed to remove just the right amount of cooper. In spite of there being a resist coating, there is no protection against etching away through exposed copper edges; this leads to over etching. Have running water ready so that the etched board can be removed properly and rinsed; this will halt etching immediate.
Now the paint is washed out by the petrol. Now the copper layout on PCB is rubbed with a smooth sand paper slowly and lightly such that only the oxide layers over the Cu is removed. Now the holes are drilled at the respective places, according to component layout as shown in figure. Drilling is one of those operation that calls for great care, because most of the holes will be made and vary small drill. For most purpose a no. 60 drill all holes with this size first those that need to be larger can be easily drilled again with the appropriate large size.
Component Assembly: There should be no damage, such as hair line crack in the copper on PCB that could have a serious effect on the operational ability of the completed assembly holes.
Some photographs:
10W Audio Amplifiers front view
10W Audio Amplifiers front view
Power supply of 10W Audio Amplifiers
If there are, than they can and should be repaired first, by soldering a short link of bare copper wire over the affected part. The most popular method of holding all the items is to bend the wires further apart after they have been inserted in the appropriate holes. This will hold the component in position ready for soldering.
Some component will be considerably larger than others, occupying and possibly partly obscuring component. Because of this, it is best to start by mounting the smallest first and progressing through to the largest, before starting, makes certain that no further drilling is likely to be necessary, because access may be impossible later. When filling each group of components, mark off each one on the components list as it is fitted and, if we have to leave the job, we will know where to recommence.
Although transistors and integrated circuits are small items, there are good reasons for leaving the soldering of these until the last step. The main point is that these components are varying sensitive to heat and if subjected to prolonged application of the soldering iron, they could be internally damaged. All the components before mounting are rubbed with sand paper so that oxide layer is removed iron their tips. Now they are mounted according to the components layout.
Project by: Sanjay Yadav, All Saints’ College Of Technology, Bhopal.
All Saints’ College Of Technology
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