Power Trade-offs and Low-Power in Analog CMOS ICs

The work presented in this book concerns power, noise and accuracy in CMOS Analogue IC Design. In the presented material it is shown that power, noise and accuracy should be treated in an unitary way, the three terms being well inter-related. This book is divided into a theoretical part which covers sub-micron digital and sub-micron analogue followed by an applicative part where accuracy related power and noise related power is encountered. The main part of this book deals with analogue circuits working in a digital environment where the process has been optimized for digital applications. The general trend, in digital, to scale down the power supply makes the process of designing analogue circuits a difficult task since most of the solutions valid for large supply voltages are not anymore useful due to the low voltage limitations. At low supply voltage, the key problem of analogue signal processing functions is dynamic range reduction. In all cases this yields in an increase of power consumption. Besides, analogue designers have to cope with second order effects generated by the incompatibility of the process with analogue performance. To get the best performance, knowing the limits of power in analog circuits and clearly defining the environment where analogue circuits should work is a must. Starting from fundamental/physical limits we are discussing the practical limits of power in digital, mostly at the architecture level and practical limits of power in analogue at circuit and architecture level. The fundamental limits are asymptotic limits and they cannot provide realistic comparisons between possible solutions. That is why the approach here provides a step further into power analysis by discussing all possible practical specs related to power at circuit and architecture level. For analogue circuits Dynamic-Range Speed product is limited by power, topology and supply voltage regardless of the type of circuits: continuous time or sampled data, current-mode or voltage mode.