How does DC input impedance at the gate of a field-effect transistor (FET) compare with that of a bipolar transistor?

توضیح

A bipolar transistor is driven through a forward-biased base-emitter junction, so its input continuously draws base current and presents a comparatively low DC impedance. An FET gate is separated from the channel by a reverse-biased junction or an insulating oxide and draws essentially no DC current, so its DC input impedance is orders of magnitude higher.