Recent Advances and Future Directions of Research - Current Conveyors: Variants, Applications and Hardware Implementations - page 526

of performance limitations such as precision, offset, noise etc. An elementary cell
of the analog arrays based upon Current Conveyor was first introduced by Premont
et al. in 1998 [ 24 ] as the first step towards producing, eventually, a fully-
integrated FPAA.
The second major step in this direction came after more than a decade when
Mahmoud and Soliman [ 25 ] presented a low-voltage, low-power FPAA in which
the configurable analog block (CAB) design was based upon a three bit digitally
controlled fully differential second generation current conveyor (DCFDCCII) and
the FPAA consisted of seven such cabs. The cabs are directly connected together in
a hexagonal lattice arrangement. The workability of the proposed FPAA has been
demonstrated by realizing a variable gain amplifier, a tunable second order low pass
filter and a tunable second order band pass filter with the DCFCCII realized by
using a fully-differential buffer, power amplifier and a three-bit CMOS current
division network. The completed FPAA was realized in 90 nm CMOS technology,
with a DC power supply voltages of 0.5 V.

In another paper by same authors [ 26 ], a similar FPAA, consisting of seven
hexagonally arranged cells was shown to realize a sixth order, tunable Butterworth
low pass filter for WLAN/WiMAX receivers with cutoff frequency tunable from
5.2 MHz to 16.9 MHz.
From these representative developments on FPAAs using digitally-
programmable fully differential current conveyors, it is apparent that this area of
research has not been explored much and there appears to be enough scope for
refining what has been developed so far or introducing new FPAA structures with
CABs based upon other varieties of CCs; for example, Universal Current Con-
veyors, Universal Voltage Conveyors, fully-balanced Current Conveyors etc.

16.5 Applications of the Current Conveyors in Realizing
Logic Functions and Digital Circuits

Undoubtedly, almost all the applications of the CCs have been in the domain of
analog circuits and functions. Recently, some attempts have been made in demon-
strating that one variety of CCs, namely, CCCII can also be employed to realize
XOR and XNOR functions; the latter by a composite connection of two CCCII + s
along with a resistor [ 27 ]. This opens a new area of research i.e. that of realizing
various logic functions and digital circuits using CCCs.