![]() Internally, all ADC circuits produce a certain amount of rms noise due to resistor noise and “ kT/ C” noise. Code-transition noise (input-referred noise) and its effect on ADC transfer function. #Sendtox free analog code#Figure 1b shows a situation where the width of the code transition noise is approximately one least-significant bit (LSB) peak-to-peak. ![]() A practical ADC has a certain amount of code transition noise, and therefore a finite transition region width. A theoretically perfect ADC has zero code-transition noise, and a transition region width equal to zero. As the analog input voltage is increased, the “ideal” ADC (shown in Figure 1a) maintains a constant output code until a transition region is reached, at which point it instantly jumps to the next value, remaining there until the next transition region is reached. Input-referred noise is certainly a departure from the ideal, and its effect on the overall ADC transfer function is shown in Figure 1. Practical ADCs deviate from ideal ADCs in many ways. Input-Referred Noise (Code-Transition Noise) If this doesn’t seem to make sense right now, read on to find out how some noise can be good noise. ![]() In most cases, less input noise is better however, there are some instances where input noise can actually be helpful in achieving higher resolution. Input-referred noise is not to be confused with quantization noise, which is only of interest when an ADC is processing time-varying signals. ![]() Is No Noise Good Noise?Īll analog-to-digital converters (ADCs) have a certain amount of input-referred noise-modeled as a noise source connected in series with the input of a noise-free ADC. ADC Input Noise: The Good, The Bad, and The Ugly. ![]()
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