Over recent years, the definition of what constitutes a precision DAC (digital-to-analog converter) has changed rapidly as semiconductor processing and on-chip calibration technologies have advanced. Not long ago, 12-bit DACs were considered to be precision devices; now widely available 16-bit accurate digital-to-analog converters are commonly used in precision medical, instrumentation, and test and measurement applications.

But even 16 bits is no longer state of the art, as 18 and even 20-bit units are available, This article looks at issues involved in using a 1-ppm (20 bit) DAC. It is presented in pdf form (no registration required) as follows:

• Part 1 of this article looks at a 1-ppm DAC and associated support circuitry, error sources, and performance measures. To read it, click here.
• Part 2 discusses 1-ppm circuit complexities including noise, temperature drift, thermoelectric voltages, physical stress, long-term stability, circuit construction and layout, and voltage references. To read it, click here.

About the author
Maurice Egan is a senior applications engineer for the precision converter group at Analog Devices, Inc. He holds a bachelor's degree in electronic engineering from the University of Limerick, Ireland. He can be reached via email at maurice.egan@analog.com.