ADC Input Noise: The Good,The Bad, and The Ugly.Is No Noise Good Noise?IntroductionAll analog-to-digital converters (ADCs) have a certain amount ofinput-referred noise—modeled as a noise source connected in serieswith the input of a noise-free ADC. Input-referred noise is notto be confused with quantization noise, which is only of interestwhen an ADC is processing time-varying signals. In most cases,less input noise is better; however, there are some instances whereinput noise can actually be helpful in achieving higher resolution.If this doesn’t seem to make sense right now, read on to find outhow some noise can be good noise.