
604 Microwave Engineering
pinches off the channel against the semi-insulating substrate towards the
drain end. With the increase of reverse bias between the source and the gate,
the height of the charge depletion region also increases. The decrease in
channel height in the pinch-off region increases the channel resistance. The
drain current I
d
is modulated by the gate voltage V
g
. This process leads to a
family of curves shown in Figure 14.19.
Transconductance: The transconductance of a FET is given as
g
dI
dV
m
d
g
V
g
=
=constant
(14.35)
For a xed drain-to-source voltage V
d
, the drain current I
d
is a function of
reverse biasing gate voltag ...