Hardware Reference
In-Depth Information
Chapter 1
The Evolution and the History of
Current
Conveyors
Abstract A historical account about the origin of Current Conveyors is given and
important developments in the area, taken place during the past four decades have
been highlighted.
1.1 Prologue
It is well recognized that in spite of the dominance of digital circuits and techniques,
analog circuits are essentially required in many situations since all natural signals
are analog. Analog circuits and techniques are hence, indispensable in realizing
signal amplifiers, continuous-time filters, rectifiers, sinusoidal oscillators, analog-
to-digital and digital-to-analog converters, analog multipliers and dividers and
some types of artificial neural networks.
In the context of modern VLSI design, the
current mode approach
to analog
circuit design has received dominant attention (see [
1
-
73
] and the references cited
therein) due to the several advantages offered by it. Current-mode circuits provide
attractive alternatives to their voltage-mode counterparts in terms of providing one
or more of the following advantageous features such as realization of intended
functions with the least possible number of external components without requiring
any component-matching conditions or equality constraints, simpler circuit struc-
tures, better accuracy in realizing the intended characteristics, higher operational
frequency range, larger dynamic range and better linearity etc.
The
Current Conveyors
(CC) invented by Sedra and Smith in the late seventies
and early eighties are now well recognised to be the most prominent current-mode
building blocks which have received worldwide attention of academicians, circuit
designers and researchers as alternative building blocks in general, and in
low-voltage, low-power circuit designs in particular. It has been now well
established that the CCs can realize most of the above mentioned analog functions
more efficiently and with several advantages than the corresponding circuits real-
ized with the traditional op-amps. Indeed, CCs have had very significant effect on
the evolution of a host of other building blocks in recent times and thus, have cast a
profound influence on the development of modern analog circuit design.
Search WWH ::
Custom Search