SIGMA-DELTA MODULATOR WITH IMPROVED GAIN ACCURACY

摘要

Sigma-delta modulator in which the gain stage (20) of the input network and the gain stage (22) of the feedback network are regularly interchanged ("chopped"). This averages out the difference between the two gain stages, thus defining the gain of the system accurately. The difference in gain between the two gain stages is modulated on the chopping frequency, which may be outside the frequency band of interest. Furthermore, by using fully differential circuitry the chopping can be effected in such a manner that the offset and flicker noise of the two gain stages are modulated to the chopping frequency.