Introduction to CMOS OP-AMPs and Comparators

CHAPTER 1

INTRODUCTION

Operational amplifiers (op-amps) and comparators are two of the most important building blocks for analog signal processing. Op-amps and a few passive components can be used to realize such important functions as summing and inverting amplifiers, integrators, and buffers. The combination of these functions and comparators can result in many complex functions, such as high-order filters, signal amplifiers, analog-to-digital (A/D) and digital-to-analog (D/A) converters, input and output signal buffers, and many more. Making the op-amp and comparator faster has always been one of the goals of analog designers. In this chapter the basic concept of digital and analog signal processing is introduced. Then a third category of signal processing, the sampled-data analog technique, which is in between the two main classifications, is described. Finally, a few representative examples are given of circuits and systems utilizing CMOS op-amps and comparators, to illustrate the great potential of these components as part of an MOS-LSI chip.

1.1 CLASSIFICATION OF SIGNAL PROCESSING TECHNIQUES [1–4]

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 ...