Fundamentals of Continuous-Time ADCs: Part One: The Continuous-Time Pipeline

This two-article series aims to give a ground-up introduction to what are now being referred to as
continuous-time
(
CT
)
ADCs
. Such ADCs incorporate inherent antialiasing and are easy to drive. These attractive attributes significantly simplify system design. The first part of this series describes the CT pipelined (CTP) ADC, which is appropriate when the oversampling ratio (OSR) is small. It turns out that the CTP is a fundamental improvement (in terms of area and power efficiency) over an antialias filter and ADC cascade. We derive the CTP architecture from the ground up and intuitively justify its superior power efficiency. The challenges with the CTP approach are described, and a comparison of a CTP with filter+ADC cascade is given.