OVERVIEW

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...