Circuit Techniques for Low-Vol

For four decades the evoluTIon of integrated circuits has followed Moore’slaw, according to which the number of transistors per square millimeter ofsilicon doubles every 18 months. At the same TIme transistors have becomefaster, making possible ever-increasing clock rates in digital circuits. Thistrend seems set to conTInue for at least another decade without slowing down.Thus, in the near future the processing power of digital circuits will conTInueto increase at an accelerating pace.For analog circuits the evolution of technology is not as beneficial. Thus,there is a trend to move signal processing functions from the analog domain tothe digital one, which, besides allowing for a higher level of accuracy, providessavings in power consumption and silicon area, increases robustness, speedsup the design process, brings flexibility and programmability, and increasesthe possibilities for design reuse. In many applications the input and outputsignals of the system are inherently analog, preventing all-digital realizations;at the very least a conversion between analog and digital is needed at the interfaces.Typically, moving the analog-digital boundary closer to the outsideworld increases the bit rate across it.In telecommunications systems the trend to boost bit rates is based on employingwider bandwidths and a higher signal-to-noise ratio. At the same timeradio architectures in many applications are evolving toward software-definedradio, one of the main characteristics of which is the shifting of the analogdigital boundary closer to the antenna.Because of these trends, there is an urgent need for data converters withincreasing conversion rates and resolution. A part of this needed performanceupgrade comes with the technology evolution, but often the demand is higherthan this alone can provide. Thus, there is still room, and a need, for innovations in circuit design.