Environmental Engineering Reference
In-Depth Information
First we evaluate the voltage partition between
and
Since we must set the node Z to ground, this is equivalent to setting
to
zero. Using this condition in (2.9b) we obtain
Then we evaluate the equivalent transconductance, by considering the
short-circuit current flowing
into
terminal Z, which is expressed by
Thus, the equivalent transconductance is found to be
where (2.8) with has been used.
Compared with the simple CX configuration, the degeneration reduces the
transconductance value, although it provides higher input and output
resistances.
The above expression is further simplified if it is possible to neglect
resistance Moreover, for bipolar transistors, or neglecting the body effect
in MOS transistors, we get the well-known result
