Analog-to-digital converters (ADCs) are central to modern audio, video, and RF systems, with some modern converters providing 23 plus -significant- bits. With such systems, performance is usually limited to audible distortion. Consequently linearity tests, analogous to distortion measurements, are adapted to test performance. The total difference-frequency distortion (TDFD) test is a modern standard for distortion measurement in the audio field, and its uniquely powerful advantages may be transferred to the realm of ADC testing. Building on existing work, a straightforward TDFD test for ADC systems is described and demonstrated. Measurements of example ADC systems are presented. A simple relationship between distortion and effective bits is derived, as a measure of performance, and testing guidelines are given.
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