Environmental Engineering Reference
In-Depth Information
It is apparent that for MOS transistor implementations
is infinite since
is infinite. Parameters
and
can be directly evaluated
from (6.7) and are given by
Thus, according to (3.24) the output resistance is
and, as expected,
compared to its open-loop
value is reduced by
approximately the loop gain.
6.1.1 Series-shunt Amplifier with Buffer
When practical design constraints lead to a feedback resistance, too
much higher than load resistance, the loop gain could become too low,
and we get a proportional reduction of the feedback benefits. This problem
can be circumvented by inserting a voltage follower between the output port
of transistor T2 and the node to which the load termination and the input
terminal of the feedback subcircuit are incident. The resultant circuit
diagram, is shown in Fig. 6.9.
