CHAPTER 4 - Analog/Digital Conversions

Abstract

This chapter discusses the different aspects of analog/digital conversions. Analog waveforms are usually defined as smooth, continuous functions that have derivatives existing nearly everywhere. Digital quantities have discrete levels that vary by steps instead of continuously. Sometimes it is necessary to represent both positive and negative integer values, as when dealing with a bipolar voltage. The most common binary code for this is called twos complement. To encode a negative value, the code for the corresponding positive value including all leading zeroes should be written, the number should be inverted by changing all ones to zeroes and all zeroes to ones, and then one should be added to the result. Data conversion is at the heart of data acquisition systems. Real-world analog signals must be converted to binary representations via an analog-to-digital converter. Similarly, if output to the analog world is required, as in control systems, digital values are transformed using a digital-to-analog converter.