Effect of additive dither on the resolution of ADC's with single-bit or multibit errors

The topic of this paper is to investigate the effects of additive dither on nonideal ADC's, i.e., ADC's with nonlinearity errors. To that end, the nonideal ADC transfer characteristics are considered as a superposition of the ideal characteristics plus nonlinearity errors. First, the factor "D" developed previously to assess the deviation of the transfer characteristics from the unity-gain line, is revisited. The nonlinearity spectra of the ideal quantization error function are then rederived using the appropriate scale factor. Second,"D" is derived for an ADC with an error in any single bit. Some example dither forms, i.e., with various probability density functions (PDF's) are considered. Effects of dither for different error levels and bit orders are investigated, and the added resolution is computed. Third, the paper investigates the effects of dither on ADC's with errors in more than one bit. The deviation factor "D" is derived, which makes it possible to compute the added resolution. The paper thus presents, for the first time, a novel technique for quantifying the performance of ADC's with multibit errors, in the presence of added dither.