Small-signal model: Difference between revisions

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m removed unnecessary word: "example" (there is no example anyway)
Overview: There was an error. Originally the paragraph said that linear components means that their current is proportional to their voltage, but that's not exactly true. In an inductor, its voltage is proportional to *the rate of change* of current (second derivative of charge w.r.t.), not to current itself (first derivative of charge w.r.t.).
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== Overview ==
Many of the [[electrical component]]s used in simple electric circuits, such as [[resistor]]s, [[inductor]]s, and [[capacitor]]s are [[linear circuit|linear]], which means the [[electric current|current]] in them is proportional to the applied [[voltage]]. Circuits made with these components, called [[linear circuit]]s, are governed by [[linear differential equation]]s, and can be solved easily with powerful mathematical methods such as the [[Laplace transform]].
 
In contrast, many of the components that make up ''electronic'' circuits, such as [[diode]]s, [[transistor]]s, [[integrated circuit]]s, and [[vacuum tube]]s are [[linear circuit|nonlinear]]; that is the current through them is not proportional to the voltage, and the output of [[two-port network|two-port]] devices like transistors is not proportional to their input. The relationship between current and voltage in them is given by a curved line on a graph, their [[Current-voltage characteristic|characteristic curve]] (I-V curve). In general these circuits don't have simple mathematical solutions. To calculate the current and voltage in them generally requires either [[graphical method]]s or simulation on computers using [[electronic circuit simulation]] programs like [[SPICE]].