Environmental Engineering Reference
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and the gain-bandwidth product is
Hence the compensation task requires that
It is worth noting that we can compensate the CFOA with a capacitance
much lower than This is a very different condition from that required in a
traditional opamp, where a high capacitance value, often impractical with IC
technologies, is needed to compensate the differentiator configuration
[WHK92], [A88], [P99].
9.7 CFOA VERSUS VOA
In this Section we make a brief comparison between the bipolar CFOA
and VOA in regard to static and frequency response performance [PP01].
The comparison assumes that actual CFOA behavior is characterized by a
dominant pole and a second equivalent pole, limiting the amplifier gain-
bandwidth product. The comparison is with a VOA of comparable topology,
thus providing similar features. The same power consumption is assumed for
both amplifiers.
The VOA topology chosen is the
folded casc
de
one shown in Fig. 9.18.
The main characteristic of this topology is, like the CFOA in Fig. 9.13,
having only one high-gain stage, since it achieves the high voltage gain
thanks to the high equivalent resistance at node A. Moreover, the full
transconductance of the input differential stage is gained by using the Wilson
current mirror T4-T6, that performs a differential-to-single conversion.
o
