SC biquad filter with hybrid utilization of OpAmp and comparator-based circuit

This paper proposes a differential switched-capacitor (SC) biquad filter exploiting a hybrid structure. The 1^st active core is an operational amplifier (OpAmp) whereas the 2^nd is an improved comparator-based circuit (CBC). The advantages of this new structure are justified by the reductions of power and transistor sizes. Optimized in a 65-nm CMOS process, when compared with a typical dual-OpAmp design, the proposed filter saves 19% power and 18% transistor area. The filter clocked at 40 MHz achieves 61.7-dB IM2 and 62.5-dB IM3 while drawing 2.23 mA from a 1.2-V supply. This hybrid SC biquad can gain further momentum for filters that request numerous biquads in cascade to attain higher selectivity.