The development of VLSI technology, together with the request of a
larger number of elements on a single chip, has led to an improved interest in
analog circuit design, especially for what concerns integrated circuits. The main
aim of analog integrated circuits (ICs) is to satisfy circuit specifications through circuit architectures with the required performance. They can be used either as“stand-alone” topologies or connected to the digital part to implement mixed analog-digital functions, utilised in a wide field of applications. Even if
numerous researchers have predicted a reduced utilisation of analog architectures and an increased development of the digital counterpart, analog circuitry continues to be necessary. In fact, analog circuits are needed in many
VLSI systems such as filters, D/A and A/D converters, voltage comparators,
current and voltage amplifiers, etc.. Moreover, new applications continue to
appear where new analog topologies have to be designed to ensure the trade-off
between speed and power requirements. Finally, the recent trend towards
miniaturized circuits has given a strong and decisive boost towards the design of
low-voltage low-power (LV LP) analog integrated circuits, which are widely
utilized in portable-system applications [1,2,3]. This has led to implement new
design circuit strategies in low-cost CMOS technology.
Since the beginning of electronics, the need of new active devices has always
been very important. It has driven to the birth of transistors which have been
used, then, in amplifiers, impedance converters, filters, etc.. In particular, the
voltage operational amplifier (OA) has rapidly become the main analog block
and has dominated the market since the advent of the first analog integrated
circuits. Nowadays, the situation is changing because there is a new impulse
towards the so called current-mode circuits [4,5,6,7], which are able to
overcome the limitation of a constant gain-bandwidth product [4,8,9] and the
trade-off between speed and bandwidth, so that performance is improved in
terms of low-voltage characteristics and of slew-rate and bandwidth.
The outline of the book is the following: firstly, the authors will talk about a
brief history of the first and second generation CC. Then, the second generation
current-conveyor (CCII) will be considered as a building block in the main
active feedback devices and in the implementation of simple analog functions,
as an alternative to OA. In the next chapters, the design of CCII topologies will
be considered together with a further look into CCII modern solutions and future
trends, in particular low offset and low noise topologies. That is why, the authors will then describe LV LP CCII implementations, their evolution towards
differential and generalized topologies, and new possible CCII applications in
some basic analog functions such as filters, impedance simulators and
converters, oscillators, etc.. Some of these implementations have been fabricated
in a standard CMOS technology. On chip measurements will be finally reported.