Introduction

Silicon technology, and in particular some variant of CMOS, will be around for many years to come [1],[2]. CMOS is the most appropriate technology for implementation of single-chip solutions, not just because of the ease of combination of RF, analogue, and digital circuits on one substrate but because of the extensive range of intellectual property (IP) available. Analogue processing will always be on chip because of the ever present need of a digital-signalprocessor (DSP) to interact with the real analogue world. For example, some 70% of all microcontroller revenue is generated by microcontrollers containing embedded analogue-to-digital converters (ADC) with a resolution of 8-bits or more [9]. Indeed, analogue-digital interfaces are rapidly becoming the performance bottle-neck to the advancement of system-on-a-chip (SoC) solutions in leading-edge CMOS processes. Moore’s Law has come to mean that the number of transistors on the same size chip doubles every two years [4] (originally every three years[3]). DSP capability has, indeed, increased by two orders of magnitude in the past decade. On the other hand, ADC resolution, for each application frequency range, has increased by only 2-bits in the same period of time! [5]. Thus, the major analogue IC design challenges are still in the area of analogue-to-digital conversion (ADC) and accompanying analogue signal conditioning circuitry [6]. There continues to be a disparity between what ADCs can deliver and what integrated digital-signal-processing systems demand. According to the latest 2005 ITRS perspective [8], at the current rate of ADC evolution, it will take another 22 years before present day all digital receivers can be fully integrated!