Basic Analog Circuit Building Blocks Using CCs and Application of CCs in Impedance Synthesis - Current Conveyors: Variants, Applications and Hardware Implementations - page 81

over four decades, to create a variety of synthetic impedances in both grounded and
floating form, for instance, see [ 4 , 5 , 9 , 10 , 12 - 22 , 24 - 45 , 47 - 59 , 61 - 65 , 68 - 72 , 74 ,
77 , 78 , 80 - 98 , 100 - 110 , 113 - 141 , 150 - 153 , 166 , 165 ].
In this chapter, we describe some of the most significant developments on the
various functional circuits mentioned above. For the interested reader, who wishes
to explore other available options than those chosen for inclusion here, a compre-
hensive list of additional references has been provided in Appendix A , at the end of
this monograph.

5.2 The Basic Functional Circuits Using CCI and CCII

Traditionally, the IC op-amp is regarded to be a versatile element and it is said that
in analog circuits area, almost anything can be realized with op-amps. However,
over the years, it has been proved that Current Conveyors are not only as versatile as
the op-amps but can outperform op-amps in many situations and applications where
the CC-based circuits require a bare minimum number of external passive compo-
nents, do not require any component-matching, do not suffer from the effects of
gain bandwidth conflict and do not have severe finite slew rate based effects
exhibited by their op-amp counterparts. It is, therefore, widely believed now that
CCs are building blocks whose time has now come. This belief has been further
strengthened by the commercial availability of CCs as off-the-shelf ICs and excel-
lent workability and versatility of several CC-based functional circuits which have
been evolved during the last four decades. In this section, we elaborate some basic
circuits which can be made from the traditional three-terminal CCs since they are
commercially available as ICs as well as can be built from other available ICs.

5.2.1 Variable-Gain Amplifiers: Constant-Bandwidth
Structures

It is well known that the traditional voltage mode op-amp (VOA) based inverting
and non-inverting amplifiers (see Fig. 5.1 ) both exhibit a conflict between the
maximum gain and 3-dB bandwidth.
The finite gain bandwidth product (GBP) of the VOA is incorporated by
representing the open-loop gain as

V 0 ¼ AV 1 ð V 2 Þ ð 5 : 1 Þ

where the open loop gain A of the op-amp is expressed as