Editing Gyrator (section)

{{short description|Two-port non-reciprocal network element}}
A '''gyrator''' is a [[passivity (engineering)|passive]], [[Linear circuit|linear]], lossless, [[two-port network|two-port]] electrical [[lumped-element model|network element]] proposed in 1948 by [[Bernard D. H. Tellegen]] as a hypothetical fifth [[linear element]] after the [[resistor]], [[capacitor]], [[inductor]] and [[transformer#Ideal transformer|ideal transformer]].<ref name="tellegen1948"/> Unlike the four conventional elements, the gyrator is [[Reciprocity (electrical networks)|non-reciprocal]]. Gyrators permit [[network synthesis filters|network realizations]] of two-(or-more)-[[Port (circuit theory)|port]] devices which cannot be realized with just the four conventional elements. In particular, gyrators make possible network realizations of [[isolator (microwave)|isolators]] and [[circulators]].<ref name="adamsetal1975"/> Gyrators do not however change the range of one-port devices that can be realized. Although the gyrator was conceived as a fifth linear element, its adoption makes both the ideal transformer and either the capacitor or inductor redundant. Thus the number of necessary linear elements is in fact reduced to three.  Circuits that function as gyrators can be built with transistors and [[op-amp]]s using [[feedback]].

[[File:tellegen-gyrator-symbol.svg|thumb|[[Bernard D. H. Tellegen|Tellegen's]] proposed symbol for his gyrator]] Tellegen invented a [[circuit symbol]] for the gyrator and suggested a number of ways in which a practical gyrator might be built.

An important property of a gyrator is that it inverts the [[current–voltage characteristic]] of an [[electrical component]] or [[electrical network|network]].  In the case of [[linear element]]s, the [[electrical impedance|impedance]] is also inverted.  In other words, a gyrator can make a [[capacitor|capacitive]] circuit behave [[inductor|inductively]], a [[LC circuit#Series LC circuit|series LC circuit]] behave like a [[LC circuit#Parallel LC circuit|parallel LC circuit]], and so on.  It is primarily used in [[active filter]] design and [[miniaturization]].