CMOS Implementations of Current Conveyors - Current Conveyors: Variants, Applications and Hardware Implementations - page 56

Chapter 4
CMOS Implementations of Current
Conveyors

Abstract In order to make CC-based circuits compatible with CMOS digital
circuits, a lot of attention has been given in the literature over the past two decades
to evolve CMOS-based Current Conveyors. In this chapter, we bring out some of
the important developments in this area.

4.1 Introduction

In the previous chapters, the main focus has been on three different ways of
realizing current conveyors (i) realization of CCs using commercially available
integrated circuits (ii) realization of CCs using architectures based upon bipolar
transistors (iii) commercially available IC implementation of current conveyors.
The circuits in all of these categories, however, are based upon the use of bipolar
junction transistors (BJT).
In view of the wide spread use of analog circuits in mixed-signal applications
and requirement of analog circuits to be integrated along with the digital circuits on
the same chip using the same technology, it is essential that there be CMOS
implementable current conveyors and CMOS implementable analog functions
using them so that they can be easily implemented in CMOS technology. Motivated
by this requirement, therefore, a number of researchers have focused upon
implementing the basic types of current conveyors namely CCI+/

by CMOS hardware [ 1 - 69 ]. In this context, however, it is worth mentioning that
simple CMOS realization of CCII+ and CCII

and CCII+/

were proposed by Sedra et al. in [ 1 ]
as early as in 1990 which are shown in Fig. 4.1a, b respectively. In this circuit
diagram, as well as elsewhere subsequently, the various MOS current mirrors and
MOS current repeaters are shown by their standard symbolic notations consisting of
two or more circles touching each other with connection to positive/negative power
supply rail(s), with input terminal shown with an arrow mark and the terminal
(s) without arrow mark being the output terminal(s).
In this chapter, we consider, therefore, CMOS realizations of basic types of
current conveyors only- a wide variety of which is scattered over dozens of
publications which have appeared during the past

three decades. Out of an