Analogue-To-Digital Conversion Techniques

56 ANALOGUE-TO-DIGITAL CONVERSION TECHNIQUES by Julian Nolan The rapid growth in the digital sector of the electronics market has given rise to continued demands for more and more increases in the resolution and conversion speed of digital-to-analogue and analogue-to-digital converters. In spite of the industry meeting these demands, the selling price of all types of device has continued to fall. This is particularly true for medium speed/resolution flash devices: an 8-bit, 30 MHz type, for instance, is now available in quantity for well under £20. Advances in the digital-to-analogue converter field have been typified by higher specifications rather than lower prices. Three main analogue-to-digital (A-D) con- version techniques are in common use: successive approximation, flash and inte- grating conversion. Successive approximation has the advantage that for an n-bit converter only n number of stages are necessary in the successive approximation register (sAR), which makes this t...