ABSTRACT
The recent tremendous advances in integrated circuit technology have made it possible to produce cheap, high-speed, reliable digital circuits. The drastically reduced feature size (now deep submicron) of very large-scale integrated (VLSI) circuits has resulted in a proportional reduction in the area of silicon dies, which operate at low voltages and consume little power. The degree of integration (packing density) has greatly increased, to the extent that a complete digital system can now be manufactured on a single chip. Processing of signals in digital format has therefore become feasible and even more economical than before. Because the majority of the signals we deal with-for example, audio, video, biomedical, and telemetry signals-are analog by nature, there has been a need for interfacing devices that can transform (convert) such signals from an analog format into a digital format, and vice versa, with minimal loss of information or added noise. The many advantages of digitally processing these signals can justify the resulting hardware, cost, and delay overheads. In this chapter, we are going to study a family of devices called data converters that includes ADCs and DACs. Preprocessing operations like band limiting and sampling, which an analog signal should undergo prior to conversion, are fi rst described. The process of quantization and the different quantization techniques are fi rst considered. Due to their simplicity, the most common realizations of DACs are then described. Circuit implementations of the different quantization techniques and ADC techniques are considered in detail, along with some design examples. As the speed and precision requirements of ADCs increase, so does the complexity of their circuit realizations. Therefore, some examples of economical architectures that feature high speed and hardware simplicity are described. Several standard qualitative and quantitative tests that are usually used to judge the performance of data converters are then presented.
