Thus for a large number of channels, it is possible that the successive approximation ADC is faster than the Wilkinson. For a successive approximation ADC, the conversion time scales with the logarithm of the number of channels. The conversion time is directly proportional to the number of channels. Currently, frequencies up to 300 MHz are possible. The Wilkinson ADC is limited by the clock rate which is processable by current digital circuits. These non-linearities reduce the dynamic range of the signals that can be digitized by the ADC, also reducing the effective resolution of the ADC. Important parameters for linearity are integral non-linearity (INL) and differential non-linearity (DNL). These errors can sometimes be mitigated by calibration, or prevented by testing. In the above example of an eight-bit ADC, an error of one LSB is 1/256 of the full signal range, or about 0.4%.Īll ADCs suffer from non-linearity errors caused by their physical imperfections, resulting in their output to deviate from a linear function (or some other function, in the case of a deliberately non-linear ADC) of their input. These errors are measured in a unit called the LSB, which is an abbreviation for least significant bit. There is also a so-called aperture error which is due to a clock jitter and is revealed when digitizing a time-variant signal (not a constant value). Quantization error and (assuming the ADC is intended to be linear) non-linearity is intrinsic to any analog-to-digital conversion.
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