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En. Ir. Chairulsyah Wasli

A device that actively boosts, or amplifies, a signal so that the output signal is a function of, and is of greater strength than, the input signal. An amplifier is a relatively simple device that transfers energy, at a controlled level, from an independent power source to an incoming signal in order to increase the strength of an outgoing signal.

the power amplifier can be defined as the final stage in multistage amplifiers, such as audio amplifiers and radio transmitters, designed to deliver appreciable power to the load. Power amplifiers may be called upon to supply power ranging from a few watts in an audio amplifier to many thousands of watts in a radio transmitter.

recognize the main properties of an operational amplifier.

understand op amp parametes input bias current and offset current and voltage

define and calculate comman mode rejection ratio and also appreciate slew rate.

define and explain the effect of parameters amplifier.

explain the principles of operation, draw the circuit diagram symbol and calculate gain for the following operational amplifier

Designers often separate a problem into a number of smaller activities. This helps focus their thoughts and make the development of the design easier to control. By breaking

the problem down into smaller sections it also helps ensure that no important features are left out.

Selection Of Problem - A number of design problems that use the Audio amplifier circuit are outlined on the Investigations page. Read the information

provided and select one of the problems to develop a solution for.

Design Brief - The design brief is a short description that clearly states the aim of the design project and in a few words states the kind of product that is needed. For example,

“Design a case” is not very helpful to a designer.“Design a case to hold a small amplifier circuit” gives the designer a clearer focus without applying restrictions.

Investigation - When a designer has isolated a problem, the next task is to find out as much background information as possible to help them develop an effective solution. A

comprehensive investigation will collect relevent information from a variety of sources that are likely to affect your product.

Specification - Once you have a clear understanding of the problem, you can work out the specification for your Amplifier. A specification is a list of things that the final design

must good specification will list the important features in order of importance

Initial Ideas- Once you have written a specification, the next stage is to draw some initial ideas. Designers try to come up with as many ideas as possible. Even if you

think the idea might be a little silly, you should include it because it may be useful later.

Construction

Evaluation

The TBA 820M audio amplifier is a low power amplifier that is capable of generating 1.2 Watts output.

The TBA 820M is an 8 pin IC, that can operate from supply voltages as low as 3V and does not consume much current when there is no signal applied. The IC also has the

advantage that there is little distortion when the signal is amplified.

Soldering equipment set

The things that need to gather together the following equipment before you start construction of your circuit.

Printed circuit board

Components: IC TBA 820M, 27Ω resistors (red-violet-red), 4.7R resistors (yellow, violet, gold) and one 56R (green, blue, black). One 330pF electrolytic capacitors. One 47uF electrolytic capacitor. Three 100uf electrolytic capacitor. One 0.1(104) ceramic capacitor. One 1µF polyester capacitor. One 8 Ohm speaker. One slide switch.

One PP3 battery snap. One 3.5mm stereo jack socket.

Solder the resistors in place.

ProcedureProcedure

Solder the smaller capacitors in place.

Solder the electrolytic capacitors into position.

Solder the LED in position. Do not forget to leave sufficient room for the LED to protrude from the case you have designed.

Solder the IC socket and jack socket into place. This may be a tight fit.

Solder the remaining external components in place taking care that if cables need to be fed through a hole in the case you have made

sure that you remember to do this.

Place the TBA820M in the IC socket.

Attach the battery and test the circuit.Attach the battery and test the circuit.

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The TBA820M is a monolithic integrated audio amplifier in a 8 lead dual in-line plastic package. Itis intended for use as low frequency class B power amplifier with wide range of supply voltage: 3 to16V, in portable radios, cassette recorders and players etc.

Main features are: minimum workingsupply voltage of 3V, low quiescent current, lownumber of external components, good ripple rejection,no cross-over distortion, low power dissipation.Output power: Po = 2W at 12V/8, 1.6W at 9V/4 and 1.2W at 9V/8.

Frequency compensation. Cb and Rf determine a low pass filter, with which you determine the upper frequency limit. Select Cb according to

Rf from Figure 7 on page 4 of the datasheet.

Gain Setting (Inverting Input). The gain is set by Rf and R5. R5 is 6k and inside the IC, look at the schematic on page 2.

Choose Rf according to what we needs.

Non-inverting input.

Pin 1Pin 1

Pin 2Pin 2

Pin 3Pin 3

Ground.

Bootstrap. Used to maintain the output signal symmetric. Refer to Figure 1 or 2 on page 1 for the correct connection.

Pin 4Pin 4

Pin 7Pin 7

Pin 8Pin 8

OutputPin 5Pin 5

Supply Voltage.Pin 6Pin 6

Ripple Rejection. Add a capacitor there, if you hear hum or buzz through your speaker that is not caused by ground loops.

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reading get from oscilloscope and digital multimeterreading get from oscilloscope and digital multimeter

reading get from oscilloscope and digital multimeterreading get from oscilloscope and digital multimeter

reading get from oscilloscope and digital multimeterreading get from oscilloscope and digital multimeter

reading get from oscilloscope and digital multimeterreading get from oscilloscope and digital multimeter

Having only one channel of amplification in a chassis is regarded as the best--but most costly--solution; it is intended to provide the utmost sound quality, all other considerations are secondary. Since everything in the box is devoted to

a single channel, a monoblock amp is generally (not always!) more powerful than a stereo or multichanel amp. There is no electrical connection between the channels except at the wall socket, and so signal seperation is maximized.

The amplifier can be placed close to the speaker (as in, within inches) minimizing the amount of speaker cable needed.

Cost: You buy a seperate amp for each channel in your system. It's not uncommon for a single monoblock to cost the same as a stereo amp.

There are those who argue that it's better to have short interconnect cables than to have short speaker cables. One thing is guaranteed:

cables or interconnect cables.

Some speakers (Polk SDA series, for example) are designed to work with amplifier channels that share a ground path for the two channels. (These speakers are not common.) Seperate amplifiers don't have that common ground connection.

You need to be able to "plug in" each amplifier seperately. Your home wiring needs to have outlets near where each amp is located. You may need to hire an

electrician to "beef up" the wiring in your house so that the monoblocks have a source of enough electrical power

The main problem with the class-B amplifier is that there is a distortion in the waveformwhere it crosses zero. The transistor characteristic becomes nonlinear as it approaches

cutoff. The transistor provides to little current as the voltage approaches zero. This causes what in known as crossover distortion. By changing the bias point so that there is a

small current flow when the signal input is zero provides an overlap between the two transistors and one transistor starts to conduct before the other turns off. If the overlap

is properly adjusted the extra current from the transistor that is just turning on will make up for the deficiency in the transistor that is turning off.

When this offset bias is used the amplifier is known as a class-AB amplifier.

The disadvantage of such amplifier is that there can be a distortion while switching of transistors takes between positive and negative values. Nowadays, many Class D

amplifiers are used in Subwoofers. They are inexpensive to build and the logic is that the switching distortion is not important in a subwoofer.

Cost: You buy a seperate amp for each channel in your system. It's not uncommon for a single monoblock to cost the same as a stereo amp.

There are those who argue that it's better to have short interconnect cables than to have short speaker cables. One thing is guaranteed: short cables do less

damage to the signal than long cables, whether we're talking speaker cables or interconnect cables.

Some speakers (Polk SDA series, for example) are designed to work with amplifier channels that share a ground path for the two channels. (These speakers are not

common.) Seperate amplifiers don't have that common ground connection.

You need to be able to "plug in" each amplifier seperately. Your home wiring needs to have outlets near where each amp is located. You may need to hire an

electrician to "beef up" the wiring in your house so that the monoblocks have a source of enough electrical power

device to convert a low-power radio-frequency signal into a larger signal of significant power, typically for driving the antenna of a transmitter

RF Power Amplifier

A family of RF power detector integrated in loop controllers for PA power control applications in cellular handsets.

Linear Power Amplifier

A power amplifier for a radio communication system is provided which includes a divider for equally dividing a received signal into two signals,

an amplifier for separately amplifying the divided signals with a same gain, and a combiner for combining the separately amplified signals

into one output signal.

FET Communication Power Amplifier

Used by American Military as a device of shooting long range missile from sky by using heat shooter.

OpamLac Power Amplifier

Used at transformer generators

Valve Amplifier Transformers

The TBA820M has two accessible feedback netmorks. The first, brought out at ICI pin 2, uses resistor R1, connected to the 0V rail via a capacitor, to control the gain. The lower the value of the blocking capacitor progressively increase feedback, and reduce gain, as frequency is lowered.

Switch S1 a connect capacitors of different value, C1,C2, nad C3, into circuit in order to produce the different levels of low-frequency attenuation.

Feedback

The second feedback networks, brought out at ICI pin 1, controls the high frequency.

The above measure by themselves have a very noticeable effect on the frequency respone of the amplifier. Roll-off at the low and high

frequency ends of the spectrum is not, however, very steep, and further measures need to be taken to increase the rate of attenuation.

Reactance

By placing a capacitor or inductor in series with the loudspeaker or phones, its reactance can be used in a more direct way to modify the

response of the system.

Output pin 5 is held at half the supply voltage, and the speaker, LS1, has to be connected via a d.c. blocking capacitors.

-Switch S1c selects capacitor of different value, C10,C11 and C12. The -smaller the value of the capacitor, the greater its reactance at low

-frequency, and the more the low frequency output to the speaker is attenuated.

Combining these measures produces the frequency response curves displayed. Becouse of the simplicity of the arrangement, response is humped

rather than flat over the speech frequency range. However, the 12dB per octave roll-off beyond the band limits greatly improves the clarity

of the signal overlaid by noise.

Response

The first level of processing curve B is usually all that is required. Background rumble is eliminated from microphone signals, and the muffled, bass-

heavy response of a critically adjusted regenerative receiver is connected.

Turning now to the actual power amplifier circuit. The potentiometer VR1 acts as the Volume control and resistor R1 pre-set the gain of the circuits. The d.c.

blocking capacitor for the input is located on the preamplifier board. If the power amplifier is used with other compenent, fit a 2.2µF electrolytic d.c.

blocking capacitor in series with the input.

Amplifier

Supply line ripple is rejected by a capacitor C4 and resistorR3 and capacitor C9 foorm a Zobel network that protects the internal output transistor

from damage by high levels transients. Stability at high and low frequency in ensured bypass capacitors.

In general, the purpose of an amplifier is to take an input signal and make it stronger or in more technically correct terms, increase its amplitude.The project that we

done is the power amplifier which are designed to drive loudspeakers.

The purpose of a power amplifier, in very simple terms, is to take a signal from a source device and make it suitable for driving a loudspeaker.Ideally, the only thing different between the input signal and the output signal is the strength of the signal.

The project of power amplifier that we done are not ideal.The output signal of all amplifiers contain additional unwanted components that are not present in the

input signal which these additional characteristics may be lumped together and are generally known as distortion.

The power amplifier that we done have the power ratings of 1 watt. This due to various load impedances the units for load impedance are ohms.The rated power output of an amplifier is understood to be its maximum output, it in no way means that the amplifier can only be used at this output. For example, if an amplifier is rated at 100 watts, the output can be anything between zero and this maximum

rated value. Chances are that the amp can probably put out more if the input signalis overdriven, however the quality of the output will degrade rapidly. as distortion.

If the amplifier is overdriven most probably the consequences of getting the speaker damage is higher.Based on the circuit diagram, the higher the resistance value of RL the higher the source power needed to achieve high power output.

Moreover the harmonic distortion also will increase with output power at a certain point. Mostly the harmonic distortion value is higher at the point of nearing the max

output power which is 1 watt for the audio power amplifier that we done.

There are three functional stages in an amplifier block which consists of power supply , input stage and output stage.The primary purpose of a power supply in a power

amplifier is to take the power from the power source and convert it to a DC voltage. This is due to semiconductor devices used inside the equipment require DC voltage.

The general purpose of the input stage of a power amplifier is to receive and prepare the input signals for amplification by the output stage.The output stage of an amplifier

is the portion which actually converts the weak input signal into a much more powerful replica which is capable of driving high power to a speaker. The output

stage of an amplifier also interfaces to the speakers.

Noise on the other hand is not been detected that much in the circuit that we done due its low power rating. Generally, the more powerful the amplifier, the more noise it will put out. If you turn on an amplifier and listen to a speaker connected

to the amplifier you can clearly hear a hissing sound. This pretty much represents the noise floor of the amplifier.

Basically audio power amplifier works as a unit of mechanism that increases a input signal strength and release it as a strong output.

Generally amplifier increases the amplitude of an audio wave from the input to blast up the speaker. The amplifier consists mainly from transistors majoring from

mosfet type of transistor.

Transistor is the main component in an amplifier to amplify the current to make it stronger at output. From here we had learned that amplifier

varies the value of a signal’s amplitude in order to make it stronger.