Driven by applications such as telecommunications, computing and consumer/multimedia and facilitated by the progress in CMOS ULSI technology, the microelectronics IC market is characterized by an ever-increasing level of integration complexity. Today complete systems, that previously occupied one or more boards, are integrated on a few chips or even on one single multi-million transistor chip - a so called System-on-Chip (SoC). Although most functions in such integrated systems are implemented with digital or digital signal processing circuitry, the analog circuits needed at the interface between the electronic system and the continuous-valued outside world are also being integrated on the same die for reasons of cost and performance.