In this chapter, the basic concept of a switched capacitor performing as a simulated resistor is introduced. Some of the physical properties of switched-capacitor circuits are also briefly discussed. Then, a comparison is made between signal processors using switched-capacitor circuits and some alternative implementations, such as discrete analog circuits, digital filters, and analog bipolar integrated circuits. Finally, a few representative examples are given of circuits and systems utilizing MOS analog signal processing techniques, to illustrate the great potential of these circuits in telecommunication systems and related applications.
Electrical signal processors are usually divided into two categories: analog and digital systems. An analog system carries signals in the form of voltages, currents, charges, and so on, which are continuous functions of the continuous time variable. Some typical examples of analog signal processors are audio amplifiers, passive- or active-RC filters, and so on. By contrast, in a digital system each signal is represented by a sequence of numbers. Since these numbers can only contain a finite number of digits (typically, coded in the form of binary digits or bits) they can only take on discrete values. Also, these numbers are the sampled values of ...