Nonlinear device
Encyclopedia
In an electric circuit
, a nonlinear element or nonlinear device is an electrical element
which does not have a linear
relationship between current
and voltage
. A diode
is a simple example. The current I through a diode is a non-linear function of the voltage V across its terminals:
Nonlinear elements are avoided in some electronic circuits, called linear circuit
s, because they have the potential to distort electrical signals.
Other examples of nonlinear elements are transistor
s and other semiconductor
devices, vacuum tube
s, and iron core inductor
s and transformer
s when operated above their saturation current. Examples of linear elements are resistor
s, capacitor
s, and air core inductor
s.
Many circuit elements that operate linearly at low signal levels will show nonlinearity at higher signal levels. An example of this can be seen in many audio systems by turning up the volume. At a high enough volume level, the transistors or other amplifying elements will begin to operate nonlinearly and distort the sound. Conversely, nonlinear elements can be made to operate linearly if the signal in them is limited to a low level. If the input of a non-linear device such as a transistor only varies in a small range around a fixed value, then the input/output relation is linearized
around this fixed value (usually called the quiescent point, Q-point, or Bias point). This is called a small signal model
.
Electronic circuit
An electronic circuit is composed of individual electronic components, such as resistors, transistors, capacitors, inductors and diodes, connected by conductive wires or traces through which electric current can flow...
, a nonlinear element or nonlinear device is an electrical element
Electrical element
Electrical elements are conceptual abstractions representing idealized electrical components, such as resistors, capacitors, and inductors, used in the analysis of electrical networks...
which does not have a linear
Linear
In mathematics, a linear map or function f is a function which satisfies the following two properties:* Additivity : f = f + f...
relationship between current
Electric current
Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...
and voltage
Voltage
Voltage, otherwise known as electrical potential difference or electric tension is the difference in electric potential between two points — or the difference in electric potential energy per unit charge between two points...
. A diode
Diode
In electronics, a diode is a type of two-terminal electronic component with a nonlinear current–voltage characteristic. A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material connected to two electrical terminals...
is a simple example. The current I through a diode is a non-linear function of the voltage V across its terminals:
Nonlinear elements are avoided in some electronic circuits, called linear circuit
Linear circuit
A linear circuit is an electronic circuit in which, for a sinusoidal input voltage of frequency f, any output of the circuit is also sinusoidal with frequency f...
s, because they have the potential to distort electrical signals.
Other examples of nonlinear elements are 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...
s and other semiconductor
Semiconductor
A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...
devices, 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...
s, and iron core inductor
Inductor
An inductor is a passive two-terminal electrical component used to store energy in a magnetic field. An inductor's ability to store magnetic energy is measured by its inductance, in units of henries...
s and transformer
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field...
s when operated above their saturation current. Examples of linear elements are resistor
Resistor
A linear resistor is a linear, passive two-terminal electrical component that implements electrical resistance as a circuit element.The current through a resistor is in direct proportion to the voltage across the resistor's terminals. Thus, the ratio of the voltage applied across a resistor's...
s, capacitor
Capacitor
A capacitor is a passive two-terminal electrical component used to store energy in an electric field. The forms of practical capacitors vary widely, but all contain at least two electrical conductors separated by a dielectric ; for example, one common construction consists of metal foils separated...
s, and air core inductor
Inductor
An inductor is a passive two-terminal electrical component used to store energy in a magnetic field. An inductor's ability to store magnetic energy is measured by its inductance, in units of henries...
s.
Many circuit elements that operate linearly at low signal levels will show nonlinearity at higher signal levels. An example of this can be seen in many audio systems by turning up the volume. At a high enough volume level, the transistors or other amplifying elements will begin to operate nonlinearly and distort the sound. Conversely, nonlinear elements can be made to operate linearly if the signal in them is limited to a low level. If the input of a non-linear device such as a transistor only varies in a small range around a fixed value, then the input/output relation is linearized
Linearization
In mathematics and its applications, linearization refers to finding the linear approximation to a function at a given point. In the study of dynamical systems, linearization is a method for assessing the local stability of an equilibrium point of a system of nonlinear differential equations or...
around this fixed value (usually called the quiescent point, Q-point, or Bias point). This is called a small signal model
Small signal model
Small-signal modeling is a common analysis technique in electrical engineering which is used to approximate the behavior of nonlinear devices with linear equations...
.