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Engineering LibreTexts

29.1: Theory Overview

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  • In many regards, JFET amplifiers share similar attributes with their bipolar counterparts. Superficially, they look very similar as well. The main functional differences are that JFET based amplifiers tend to have higher input impedances but tend to offer lower voltage gains. Further, without swamping, JFET amplifiers tend to produce lower levels of distortion. As with \(r'_e\) impacting bipolar circuit performance, JFET performance is impacted by the transconductance, \(g_m\) (AKA \(g_{fs}\)). Like the bipolar common emitter amplifier, the common source amplifier exhibits a voltage gain greater than one with inversion. The source follower, like the bipolar emitter follower, shows a voltage gain just under one with no inversion.

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