Environmental Engineering Reference
In-Depth Information
where is the mobility of electrons near the silicon surface.
Substituting (1.22) in (1.25) yields
Larger drain voltages modify the charge density profile in the channel.
Specifically, referring to Fig. 1.7, we can express the channel charge density
as a function of channel length. For
x =
0, that is, close to the source, (1.22)
holds, while for
x = L,
that is, close to the drain, we have
Assuming a linear profile, the charge density has the following
expression
The current can be expressed in a form similar to (1.25) but with a
different charge expression. If the charge density profile is linear, the
average charge density can be used instead. The average charge density
results in
