Small-signal model: Difference between revisions

Revision as of 07:49, 20 July 2018

Revision as of 23:42, 22 July 2018

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The small signal model is dependent on the DC bias currents and voltages in the circuit (the [[Q point]]). Changing the bias moves the operating point up or down on the curves, thus changing the equivalent small-signal AC resistance, gain, etc. seen by the signal.

Any nonlinear component whose characteristics are given by a [[continuity (mathematics)|continuous]], [[single valued]], smooth ([[differentiability|differentiable]]) curve can be approximated by a linear small-signal model. Small-signal models exist for [[Vacuum tube|electron tube]]s, [[diode]]s, [[field-effect transistor]]s (FET) and [[Bipolar junction transistor|bipolar transistors]], notably the [[hybrid-pi model]] and various [[two-port network]]s. Manufacturers often list the small-signal characteristics of such components at "typical" bias values on their data sheets.

==Variable notation==