Varieties of Current Conveyors - Current Conveyors: Variants, Applications and Hardware Implementations - page 325

A CMOS realization of the DXCCII was also suggested by Zeki and Toker in
[ 51 ]. Other interesting variants and applications of the DXCCII can be found in
[ 52 - 55 ].

10.2.16 Fully-Balanced CCII

The notion of a fully- balanced Second generation Current Conveyor (FBCCII) was
introduced by Alzaher et al. in 2003 in [ 56 ].
They demonstrated that such a building block can be constructed from a fully-
balanced differential difference amplifier (FBDDA) through power supply current
sensing technique. An FBCCII can be described by the same equations as a CCII+,
however, all signals are differential i. e. V x ¼ V xp V xn ,V y ¼ V yp V yn ,

I x ¼ I zn .

It was emphasized that an FBCCII can be used to implement the fully differential
version of any single ended architecture using conventional CCII. The operation and
applications of a CMOS chip demonstrated the utility of the concept (Fig. 10.15 ).

I xp I xn and I z ¼ I zp

10.2.17 Extended Current Conveyors

The extended Current Conveyors were introduced by Sato et al. in [ 55 ] as relaxed
versions of the conventional CCs with current and voltage offsets allowed apart
from the normal Current Controlled Current Sources and Voltage controlled volt-
age sources incorporated in the internal architecture of Current Conveyors. It was
shown that this results in much simpler transistor level implementations of the
extended CCs as compared to normal CCs. In most general form, the extended CC
defined by them has the following characterization:

2 3 2 3 2 3 2 3

V x
I y
I z

010
ˆ

I x
V y
V z

V offsetx
I offsety
I offsetz

4 5 ¼ 4 5 4 5 þ 4 5

00 ð 10 : 18 Þ

ʲ 00

Two specific examples would suffice to demonstrate as to how the number of
MOSFETs is reduced in making the extended CCs with relaxed definitions. Con-
sider the two exemplary MOSFET-based extended CCs from [ 55 ], which are
reproduced here in Fig. 10.16 .
The first circuit of Fig. 10.16a is perhaps the simplest CC which is realizable by
only four MOSFETs and is characterized by: