Walt Kester
Analog Devices

Selecting the proper ADC for a particular application appears to be a formidable task, considering the thousands of converters currently on the market. A direct approach is to go right to the selection guides and parametric search engines, such as those available on the Analog Devices website. Enter the sampling rate, resolution, power supply voltage, and other important properties, click the "find" button, and hope for the best. But it's usually not enough. How does one deal with a multiplicity of apparent "best choices"? Is there a way to approach the task with greater understanding—and better results?

Most ADC applications today can be classified into four broad market segments: (a) data acquisition, (b) precision industrial measurement, (c) voiceband and audio, and (d) "high speed" (implying sampling rates greater than about 5 MSPS). A very large percentage of these applications can be filled by successive-approximation (SAR), sigma-delta, and pipelined ADCs. A basic understanding of these, the three most popular ADC architectures—and their relationship to the market segments—is a useful supplement to the selection guides and search engines.