This article is about electronic amplifiers. A 100 watt stereo audio ic power amplifier pdf used in home component audio systems in the 1970s.
An amplifier uses electric power from a power supply to increase the amplitude of a signal. The amount of amplification provided by an amplifier is measured by its gain: the ratio of output to input. An amplifier is a circuit that can give a power gain greater than one. An amplifier can either be a separate piece of equipment or an electrical circuit contained within another device.
Amplification is fundamental to modern electronics, and amplifiers are widely used in almost all electronic equipment. Amplifiers can be categorized in different ways. One is by the frequency of the electronic signal being amplified. A further distinction is whether the output is a linear or nonlinear representation of the input.
The first practical device that could amplify was the triode vacuum tube, invented in 1906 by Lee De Forest, which led to the first amplifiers around 1912. 1970s when the transistor, invented in 1947, replaced them. Today, most amplifiers use transistors, but vacuum tubes continue to be used in some applications. De Forest’s prototype audio amplifier of 1914.
5, providing a total gain of approximately 125 for this three-stage amplifier. The development of audio communication technology in form of the telephone, first patented in 1876, created the need to increase the amplitude of electrical signals to extend the transmission of signals over increasingly long distances.
In telegraphy, this problem had been solved with intermediate devices at stations that replenished the dissipated energy by operating a signal recorder and transmitter back-to-back, forming a relay, so that a local energy source at each intermediate station powered the next leg of transmission. Duplex transmission was essential for telephony and the problem was not satisfactorily solved until 1904, when H.
Shreeve of the American Telephone and Telegraph Company improved existing attempts at constructing a telephone repeater consisting of back-to-back carbon-granule transmitter and electrodynamic receiver pairs. The Shreeve repeater was first tested on a line between Boston and Amesbury, MA, and more refined devices remained in service for some time. After the turn of the century it was found that negative resistance mercury lamps could amplify, and were also tried in repeaters.