A power efficient multi-rate multi-stage Comb decimation filter for mono-bit and multi-bit /spl Sigma//spl Delta/ A/D converters is presented. Polyphase decomposition in all stages, with high decimation factor in the first stage, is used to significantly reduce the sampling frequency of the Comb filter. Several implementations indicate that proper choice of the first stage decimation factor can considerably improve power consumption, area and maximum sampling frequency. In multibit /spl Sigma//spl Delta/ A/Ds, this optimum first stage decimation factor is function of the input wordlength.