
168
a negative bias to the gate repels electrons present in the channel,
reducing its conductivity, and ultimately cutting off drain current
entirely. The characteristic curves are therefore similar to those for
jugfets (Fig. 10.15) except that the zero-K
G
curve is usually much
lower, but because the gate is insulated it can be used to increase as
well as reduce the drain current. Doing this with a jugfet would
drastically reduce the input resistance.
In an enhancement igfet the channel is missing, so with no gate
bias there is no conduction between source and drain. This feature is
indicated in its symbol (Fig. 10.16c) by the gaps between