A power efficient multirate multistage Comb decimation filter for mono-bit and multi-bit $\Sigma \Delta$ 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 $\Sigma \Delta$ A/Ds, this optimum first stage decimation factor is a function of the input wordlength.