When people refer to "amplifiers," they're usually talking about stereo components or musical equipment. But this is only a small representation of the spectrum of audio amplifiers.
There are actually amplifiers all around us. You'll find them in televisions , computers , portable CD players and most other devices that use a speaker to produce sound. Sound is a fascinating phenomenon. When something vibrates in the atmosphere, it moves the air particles around it. Those air particles in turn move the air particles around them, carrying the pulse of the vibration through the air. Our ears pick up these fluctuations in air pressure and translate them into electrical signals the brain can process.
Electronic sound equipment works the same basic way. It represents sound as a varying electric current. Broadly speaking, there are three steps in this sort of sound reproduction:.
As you can see, all the major components in this system are essentially translators: They take the signal in one form and put it into another.
In the end, the sound signal is translated back into its original form, a physical sound wave. This means it is very thin and moves only a short distance. Consequently, the microphone produces a fairly small electrical current.
This is fine for most of the stages in the process -- it's strong enough for use in the recorder, for example, and it is easily transmitted through wires.
But the final step in the process -- pushing the speaker cone back and forth -- is more difficult. To do this, you need to boost the audio signal so it has a larger current while preserving the same pattern of charge fluctuation. This is the job of the amplifier. It simply produces a more powerful version of the audio signal. In this article, we'll see what amplifiers do and how they do it. Amplifiers can be very complex devices, with hundreds of tiny pieces, but you can get a clear picture of how an amplifier works by examining the most basic components.
In this next section, we'll look at the basic elements of amplifiers. In the last section, we saw that an amplifier's job is to take a weak audio signal and boost it to generate a signal that is powerful enough to drive a speaker. This is an accurate description when you consider the amplifier as a whole, but the process inside the amplifier is a little more complex. In actuality, the amplifier generates a completely new output signal based on the input signal.
You can understand these signals as two separate circuits. The output circuit is generated by the amplifier's power supply , which draws energy from a battery or power outlet. If the amplifier is powered by household alternating current , where the flow of charge changes directions, the power supply will convert it into direct current , where the charge always flows in the same direction.
The power supply also smoothes out the current to generate an absolutely even, uninterrupted signal. The output circuit's load the work it does is moving the speaker cone.
The input circuit is the electrical audio signal recorded on tape or running in from a microphone. Its load is modifying the output circuit. It applies a varying resistance to the output circuit to re-create the voltage fluctuations of the original audio signal.
In most amplifiers, this load is too much work for the original audio signal. For this reason, the signal is first boosted by a pre-amplifier , which sends a stronger output signal to the power amplifier. A power amplifier is an electronic amplifier designed to increase the magnitude of power of a given input signal. The power of the input signal is increased to a level high enough to drive loads of output devices like speakers, headphones, RF transmitters etc.
The input signal to a power amplifier needs to be above a certain threshold. You can observe the block diagram of an audio amplifier and the usage of power amplifier below. In this case, a microphone is used as an input source.
The magnitude of signal from the microphone is not enough for the power amplifier. So, first it is pre-amplified, where its voltage and current are increased slightly. Then the signal is passed through a tone and volume control circuit, which makes aesthetic adjustments to the audio waveform. Finally, the signal is passed through a power amplifier and the output from power amp is fed to a speaker. Depending on the type of output device that is connected, power amplifiers are divided into the following three types:.
This type of power amplifiers are used for increasing the magnitude of power of a weaker audio Signal. The amplifiers used in speaker driving circuitries of televisions, mobile phones etc. Wireless transmissions require modulated waves to be sent over long distances through air.
The signals are transmitted using antennas and the range of transmission depends on the magnitude of power of signals fed to the antenna. For wireless transmissions like FM broadcasting, antennas require input signals at thousands of kilowatts of power. Here, Radio Frequency Power amplifiers are employed to increase the magnitude of power of modulated waves to a level high enough for reaching the required transmission distance.
They are used in electronic control systems which need high power signals to drive motors or actuators. They take input from microcontroller systems, increase its power and feed the amplified signal to DC motors or Actuators. There are multiple ways of designing a power amplifier circuit. The operation and output characteristics of each of the circuit configurations differs from one another.
To differentiate the characteristics and behavior of different power amplifier circuits, Power Amplifier Classes are used in which, letter symbols are assigned to identify the method of operation. They are broadly classified into two categories.
The most commonly used power amplifiers are the ones used in audio amplifier circuits and they come under classes A, B, AB or C. Analog waveforms are made up of positive highs and negative lows. Tweet Share Email. In This Article. Channel Configurations.
Connecting a Power Amplifier. With a Home Theater Receiver. Power vs. Integrated Amplifiers. Why Use a Power Amplifier. Was this page helpful? Thanks for letting us know! Email Address Sign up There was an error. Please try again. You're in! Thanks for signing up. There was an error. Tell us why! More from Lifewire. Home Theater Receiver Connections Explained. Your Privacy Rights. To change or withdraw your consent choices for Lifewire. At any time, you can update your settings through the "EU Privacy" link at the bottom of any page.
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