ADC Input Noise: The Good, The Bad, and The Ugly. Is No Noise Good Noise?

All 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. Input-referred noise is not to be confused with quantization noise, which is only of interest when an ADC is processing time-varying signals. In most cases, less input noise is better; however, there are some instances where input noise can actually be helpful in achieving higher resolution. If this doesn't seem to make sense right now, read this article to find out how some noise can be good noise.