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Practical considerations of ADC circuitsWhen selecting an ADC for a particular application one has to consider three different parameters which control the performance of an ADC (and thus its costs):
An ideal ADC has a great many bits for very fine resolution, samples at lightningfast speeds, and recovers from steps instantly. It also, unfortunately, doesn't exist in the real world. Of course, any of these traits may be improved through additional circuit complexity, either in terms of increased component count and/or special circuit designs made to run at higher clock speeds. Different ADC technologies, though, have different strengths. Here is a summary of them ranked from best to worst: Resolution/complexity ratio: Singleslope integrating, dualslope integrating, counter, tracking, successive approximation, flash. Speed: Flash, tracking, successive approximation, singleslope integrating & counter, dualslope integrating. Step recovery: Flash, successiveapproximation, singleslope integrating & counter, dualslope integrating, tracking.
Please bear in mind that the rankings of these different ADC technologies depend on other factors. For instance, how an ADC rates on step recovery depends on the nature of the step change. A tracking ADC is equally slow to respond to all step changes, whereas a singleslope or counter ADC will register a hightolow step change quicker than a lowtohigh step change. Successiveapproximation ADCs are almost equally fast at resolving any analog signal, but a tracking ADC will consistently beat a successiveapproximation ADC if the signal is changing slower than one resolution step per clock pulse. I ranked integrating converters as having a greater resolution/complexity ratio than counter converters, but this assumes that precision analog integrator circuits are less complex to design and manufacture than precision DACs required within counterbased converters. Others may not agree with this assumption.


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