Real-world data are generally converted by sensors into analog electrical signals corrupted by noise. In this case, the extraction of useful information, which can be displayed by actuators, requires the use of complex algorithms, whose eﬃcient implementation exploits the programmability and ﬂexibility of digital circuits. The suitable level and representation of sensor output information are provided by signal conditioning and interface structures. In communication systems, the tasks of signal processing generally encountered in the front-end and back-end sections of a digital signal processor, namely, ampliﬁcation of the desired channel to the full-scale of the data converters, automatic gain control, and ﬁltering to remove the interference of the adjacent channels, are preferably implemented using continuous-time (CT) circuits, which oﬀer the advantages of high-speed operation and low-power consumption. Other applications include anti-aliasing and smoothing ﬁlters, channel equalization in magnetic disk drives, and high-speed data links.