AudioBahn Electronic Amplifier

AudioBahn Electronic Amplifier

An electronic amplifier is a device for increasing the power of a signal. It does this by taking power from a power supply and controlling the output to match the input signal shape but with a larger amplitude. An idealized amplifier can be said to be "a piece of wire with gain", as the output is an exact replica of the input, but larger.

Classification of amplifier stages and systems
Different designs of amplifiers are used for different types of applications and signals. We can broadly divide amplifiers into three categories:

Small signal amplifiers,
Low frequency power amplifiers and
Radio frequency RF power amplifiers.
Each of these calls for a slightly different design approach, mainly because of the physical limitations of the components used to implement the amplifier, and the efficiencies that can be realised.

There are many alternative classifications that address different aspects of amplifier designs, and they all have some effect on the design parameters and objectives of the circuit. Amplifier design is always a compromise of numerous factors, such as cost, amount of power consumed, devices that have real-world imperfections, and the need to match the amplifier to the input signal as well as the output load.


Classification of amplifier stages by common terminal

One set of these classifications include terms referring to “common terminal” connections, where the design is described by the terminal of the active device that is tied closest to ground. Examples include terms such as common emitter, common plate, or common drain, and these names also reflect the type of active device used to amplify the signal. For instance, common emitter refers to an amplifier with a bipolar transistor as the active device, while common plate would be for a vacuum tube amp, while a common drain amp would signify the use of MOSFET or JFET devices. Designs exist for almost any terminal of any active device to be held to ground in an amplifier, for different reasons that are reflected in each use. See also: common collector, common base.


Inverting or non-inverting

Another way to classify amps is the phase relationship of the input signal to the output signal. An inverting amplifier produces an output that is 180 degrees out of phase of the input signal, or a mirror image of it if viewed on an oscilloscope. A non-inverting amplifier maintains equal phase relationship between the input and output waveforms. An emitter follower is a type of this amplifier, indicating that the signal at the emitter of a transistor is following (matching phases) with the input signal.

This description can apply to a single stage or a complete system.


Function

Other amps may be classified by their function or output characteristics. These functional descriptions usually apply to complete amplifier systems or sub-systems and rarely to individual stages.

A servo amp indicates an integrated feedback loop to actively control the output at some desired level. A DC servo indicates use at frequencies down to DC levels, where the rapid fluctuations of an audio or RF signal do not occur. These are often used in mechanical actuators, or devices such as DC motors that must maintain a constant speed or torque. An AC servo amp can do this for some ac motors.

A linear amp denotes that it has a precise amplification factor over a wide range of frequencies, and is often used to boost signals for relay in communications systems. A non-linear amp is made to amplify only a specific narrow or tuned frequency, to the exclusion of all other frequencies.

A RF amp refers to an amp designed for use in the radio frequency range of the electromagnetic spectrum, and is often used to increase the sensitivity of a receiver or the output power of a transmitter.
An audio amp is designed for use in reproducing audio frequencies, with special considerations made for driving speakers. These often have multiple amps grouped together as separate or bridgeable channels to accommodate different audio reproduction requirements.

A special type of low power amp with almost ideal characteristics is used in instruments and for signal processing, among many other varied uses. These are known as operational amplifiers, or op-amps. This is because this type of amplifier is used in circuits that perform mathematical algorithmic functions, or "operations" on input signals to obtain specific types of output signals.

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