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Revision as of 20:13, 1 August 2005 by Light current (talk | contribs) (added para on relays as amplifiers (see defn of amplifier))(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)An amplifier can be considered to be any device that uses a small amount of energy to control a larger amount, althoug the term today usually refers to an electronic amplifier. The relationship of the input to the output of an amplifier--usually expressed as a function of the input frequency--is called the transfer function of the amplifier, and the magnitude of the transfer function is termed the gain.
Amplifiers are typically utilized over a specific range of frequencies and are generally of maximal utility if the gain is constant in that range.
Electrical Relays
These very common devices can be included under the above definition of amplifiers although their transfer function is not linear
Electronic Amplifiers
The most common type of amplifier is the electronic amplifier, commonly used in radio and television transmitters and receivers, high-fidelity ("hi-fi") stereo equipment, microcomputers and other electronic digital equipment, and guitar and other instrument amplifiers. Its critical component is an active device, such as a vacuum tube or transistor.
Transistor Amplifers
Most common actice devices in transistor amplifiers are bipolar junction transistors (BJTs); metal oxide semiconductor field-effect transistors (MOSFETs) are also used. The essential role of this active element is to magnify an input signal to yield a significantly larger output signal. The amount of magnification (the "forward gain") is determined by the external circuit design as well as the active device.
Vacuum Tube (Valve)Amplifiers
In the earlier years of audio, vacuum tubes filled the active device role.
Operational Amplifiers (OP-AMPS)
An Operational Amplifier is a solid state integrated circuit amplifier which employs external feedback for control of its transfer function or gain
Fluidic amplifiers
Another type of amplifier is the fluidic amplifier, based on the fluidic triode.
Other Amplifier Types
There are also mechanical amplifiers, such as the automotive servo used in braking.See also: low noise amplifier.
External links
- The Audio Circuit - Information on and user reviews of loudspeakers, headphones, amplifiers, and playback equipment