An amplifier is a device, usually electronic, that magnifies information to a more powerful signal at the amplifier's output. Amplifiers are usually based on electronic principles but may utilize hydraulics or magnetics.
Amplifiers are used when the electrical power of a signal must be increased. Audio amplifiers can increase the microwatts developed by a microphone to more than a million watts of power required to fill a stadium during a concert. Satellites use amplifiers to strengthen television and telephone signals so they can be received easily when beamed back to Earth.
Long-distance telephone circuits were made possible when amplifiers magnified power that had been dissipated by the resistance of cross-country phone wires. Amplifiers were also needed to restore lost volume. Undersea telephone cables require amplifiers beneath the sea. Cable-television systems require as many as 100 sophisticated broad-band width amplifiers to serve subscribers.
Efficiency
No amplifier can be 100% efficient. All amplifiers waste some of the energy supplied to them. For instance, an amplifier's efficiency may be improved, but the result may be increased distortion in the final output.
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