Varieties of Current Conveyors - Current Conveyors: Variants, Applications and Hardware Implementations - page 316

10.2.7 Differential-Voltage Current Conveyor

When Elwan and Soliman introduced a CMOS differential voltage current con-
veyor (DVCC) in 1997 [ 17 ] it went almost unnoticed that the basic idea of the
DVCC was introduced by Pal [ 18 ] as early as in 1989 itself and had demonstrated
its advantage in realizing lossless floating inductors. The DVCC is a four port
building block with there being two Y-terminals with flexibility that a differential
Y-input can be applied. A DVCC is, thus, characterized by the terminal equations:

and i z ¼

i y 1 ¼ i y 2 ¼ 0, v x ¼ v y 1 v y 2 i x ð 10 : 8 Þ

In retrospection, a DVCC can also be looked upon as a special case of DDCC with
the third Y-input grounded.
In the available literature, a number of CMOS realizations of the DVCC have
been proposed, for example see, [ 17 , 19 - 23 ]. As demonstrated by Elwan and
Soliman in [ 17 ], the DVCCs are particularly attractive in realizing grounded to
floating positive impedance converter, grounded to floating negative impedance
converter, floating generalized negative impedance converter and floating general-
ized positive impedance inverter/gyrator and MOS transconductor, to name a few
(see Fig. 10.10 ).
In addition to the above quoted applications, DVCCs have been found to be
equally efficient in realizing instrumentation amplifiers, floating inductors and
FDNRs, universal VM/CM filters and relaxation oscillators and waveform gener-
ators [ 17 - 25 ]. It is interesting to note that the adjoint of a DVCC is an element
called balance output CCII (BOCCII) [ 24 ] characterized by i y ¼ 0, v x ¼ v y ,i z+ ¼ +i x

and i z- ¼ i x .

10.2.8 Inverting CCIIs

In 1999, Awad and Soliman [ 26 ] introduced the inverting second generation current
conveyors as the missing building blocks characterized by v x ¼ v y ,i y ¼ 0 and i z ¼

i x thereby leading to two varieties of inverting current conveyors namely ICCII+
and ICCII .

It is interesting to point out that it went completely unnoticed by Awad and
Soliman, as well as most of the other researchers who have been using ICCII+ as a
building block that this variant of the CCII was already conceived much earlier by
Chong and Smith (see reference [5] of Chap. 6 ) wherein they called this version of
CC as the new type of CC, termed CCIIB which was employed by them in realizing
one of the special cases of their single-CC biquads. Nevertheless, Awad and
Soliman were the first to demonstrate that the new pathological elements current-
mirror and voltage-mirror introduced by them together with the nullator and the
norator were sufficient to model CCII+, CCII , ICCII+ and ICCII without