Environmental Engineering Reference
In-Depth Information
The DC open loop gain results as
and if resistance
is much greater than
it simplifies to
This shows that unlike for voltage-mode operational amplifiers, resistance
if properly dimensioned, must not be considered as a component of the
feedback network.
The dominant pole is created at the high resistance node, Z. It is simply
expressed by
and the gain-bandwidth product is
Equation (9.26) shows the well-known property of CFOAs: the closed-
loop bandwidth is independent of the closed-loop gain provided that
resistance is maintained constant. It is apparent that we have the highest
gain-bandwidth product when which means the CFOA is in unity-
gain configuration. Thus, in order to guarantee stability with safe margins,
we have to compensate the CFOA in the unity-gain configuration as for the
traditional voltage operational amplifier. Moreover, compensation can be
achieved by adopting the dominant pole approach, which requires a suitable
