Sigma-delta analog/digital converter with adaptive dither

An analog/digital .SIGMA..DELTA. converter has an input fed with an analog input signal, an output producing a digital signal representative of the analog input signal and a circuit for generating a dithering signal of amplitude adaptively regulated depending on the amplitude of the analog input signal. A comparator performs the regulation and uses a white noise dithering signal that is digitally generated and thereafter converted into an analog white noise dithering signal subjected to a second order filtering.