Environmental Engineering Reference
In-Depth Information
while the value of
depends on the substrate doping concentration as
follows [1]
1.3.5
p-channel Transistors
For a p-channel transistor we can use the same equations derived in the
previous sections, provided that a negative sign is placed in front of every
voltage variable.
Therefore, becomes becomes becomes and so
on. Note that in a p-MOS transistor the threshold voltage is negative. The
condition for a p-MOS to be in saturation region is now
Current equations (1.30) and (1.34) still hold but the current now flows from
the source to the drain.
1.3.6
Saturation Region Small Signal Model
The low-frequency small signal model for a MOS transistor operating in
the active region is shown in Fig. 1.9.
The most important small signal component is the dependent current
generator,
whose transconductance,
isdefined as
Solving (1.33) for
yields
