Editing Electrical network (section)

==Classification==

===By passivity===
An active network contains at least one [[voltage source]] or [[current source]] that can supply energy to the network indefinitely. A [[Passivity (engineering)|passive]] network  does not contain an active source.

An active network contains one or more sources of [[electromotive force]]. Practical examples of such sources include a [[Electric battery|battery]] or a [[Electric generator|generator]]. Active elements can inject power to the circuit, provide power gain, and control the current flow within the circuit.

Passive networks do not contain any sources of electromotive force. They consist of passive elements like resistors and capacitors.

===By linearity===
[[Linear circuit|Linear]] electrical networks, a special type consisting only of sources (voltage or current), linear lumped elements (resistors, capacitors, inductors), and linear distributed elements (transmission lines), have the property that signals are [[Superposition principle|linearly superimposable]].  They are thus more easily analyzed, using powerful [[frequency domain]] methods such as [[Laplace transform]]s, to determine [[direct current|DC response]], [[alternating current|AC response]], and [[transient response]].

Passive networks are generally taken to be linear, but there are exceptions.  For instance, an [[inductor]] with an iron core can be driven into [[Saturation (magnetic)|saturation]] if driven with a large enough current.  In this region, the behaviour of the inductor is very non-linear.

===By lumpiness===
Discrete [[passive component]]s (resistors, capacitors and inductors) are called ''lumped elements'' because all of their, respectively, resistance, capacitance and inductance is assumed to be located ("lumped") at one place.  This design philosophy is called the [[lumped-element model]] and networks so designed are called ''lumped-element circuits''.  This is the conventional approach to circuit design.  At high enough frequencies, or for long enough circuits (such as [[Electric power transmission|power transmission lines]]), the lumped assumption no longer holds because there is a significant fraction of a [[wavelength]] across the component dimensions.  A new design model is needed for such cases called the [[distributed-element model]].  Networks designed to this model are called ''[[distributed-element circuit]]s''.

A distributed-element circuit that includes some lumped components is called a ''semi-lumped'' design.  An example of a semi-lumped circuit is the [[combline filter]].