In this chapter, to improve the reliability and cost of signal processing electronics, entire systems must be integrated on to a single chip. In many applications, an all-digital or all-analogue system is impossible because both analogue and digital external interfaces are required. So we must assume that both analogue and digital circuits will have to coexist on the same IC. The advance of digital process technologies will enable faster digital signal processing with a smaller integrated circuit area and lower power consumption. At the same time it will become increasingly difficult to implement accurate and linear analogue circuits. Therefore, analogue adaptive filters are likely to continue to be targeted at applications where they can simplify or reduce the analogue circuitry required elsewhere on the chip.