Linear range
Encyclopedia
The linear range is that range of input or output values for which an electronic
amplifier
produces an output signal that is a direct, linear
function of the input signal. That is, the output can be represented by the equation:
When operating in the linear range, no clipping
occurs. If an amplifier were perfectly linear, no distortion
(harmonic distortion
or intermodulation distortion) would occur (although random noise
may still be introduced).
Vacuum tube
amplifiers tend to exhibit soft clipping; as they approach the maximum possible output value, the gain tends to drop, rounding the tops of the signal waveform
. Transistor
amplifiers, by comparison, tend to produce hard clipping; the gain remains approximately the same until the maximum possible output voltage is reached; at that point, hard clipping occurs and the waveform never exceeds that value. The sharp inflection point
s thus produced in the output waveform tend to have many more high-order harmonic
s. This is alleged to be the basis of the "transistor sound" that some audiophile
s find offensive (although this would not have occurred if they would not have been driving their amplifiers beyond the linear range in the first place).
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...
amplifier
Amplifier
Generally, an amplifier or simply amp, is a device for increasing the power of a signal.In popular use, the term usually describes an electronic amplifier, in which the input "signal" is usually a voltage or a current. In audio applications, amplifiers drive the loudspeakers used in PA systems to...
produces an output signal that is a direct, linear
Linear
In mathematics, a linear map or function f is a function which satisfies the following two properties:* Additivity : f = f + f...
function of the input signal. That is, the output can be represented by the equation:
- Output = Input × Gain
When operating in the linear range, no clipping
Clipping (audio)
Clipping is a form of waveform distortion that occurs when an amplifier is overdriven and attempts to deliver an output voltage or current beyond its maximum capability...
occurs. If an amplifier were perfectly linear, no distortion
Distortion
A distortion is the alteration of the original shape of an object, image, sound, waveform or other form of information or representation. Distortion is usually unwanted, and often many methods are employed to minimize it in practice...
(harmonic distortion
Total harmonic distortion
The total harmonic distortion, or THD, of a signal is a measurement of the harmonic distortion present and is defined as the ratio of the sum of the powers of all harmonic components to the power of the fundamental frequency...
or intermodulation distortion) would occur (although random noise
Noise
In common use, the word noise means any unwanted sound. In both analog and digital electronics, noise is random unwanted perturbation to a wanted signal; it is called noise as a generalisation of the acoustic noise heard when listening to a weak radio transmission with significant electrical noise...
may still be introduced).
Vacuum tube
Vacuum tube
In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...
amplifiers tend to exhibit soft clipping; as they approach the maximum possible output value, the gain tends to drop, rounding the tops of the signal waveform
Waveform
Waveform means the shape and form of a signal such as a wave moving in a physical medium or an abstract representation.In many cases the medium in which the wave is being propagated does not permit a direct visual image of the form. In these cases, the term 'waveform' refers to the shape of a graph...
. Transistor
Transistor
A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...
amplifiers, by comparison, tend to produce hard clipping; the gain remains approximately the same until the maximum possible output voltage is reached; at that point, hard clipping occurs and the waveform never exceeds that value. The sharp inflection point
Inflection point
In differential calculus, an inflection point, point of inflection, or inflection is a point on a curve at which the curvature or concavity changes sign. The curve changes from being concave upwards to concave downwards , or vice versa...
s thus produced in the output waveform tend to have many more high-order harmonic
Harmonic
A harmonic of a wave is a component frequency of the signal that is an integer multiple of the fundamental frequency, i.e. if the fundamental frequency is f, the harmonics have frequencies 2f, 3f, 4f, . . . etc. The harmonics have the property that they are all periodic at the fundamental...
s. This is alleged to be the basis of the "transistor sound" that some audiophile
Audiophile
An audiophile is a person who enjoys listening to recorded music, usually in a home. Some audiophiles are more interested in collecting and listening to music, while others are more interested in collecting and listening to audio components, whose "sound quality" they consider as important as the...
s find offensive (although this would not have occurred if they would not have been driving their amplifiers beyond the linear range in the first place).