Design of current-mode gm-C MLF elliptic filters for wireless receivers

Two CMOS fifth-order gm-C elliptic lowpass filters based on the current-mode multiple loop feedback (MLF) leap-frog (LF) and follow-the-leader-feedback (FLF) configurations are designed. The filters are implemented using a fully-differential linear operational transconductance amplifier (OTA). PSpice simulations using a standard TSMC 0.18mum CMOS process with 1.8V power supply have shown that the cut-off frequency of both filters can be tuned from 28MHz to 44MHz, dynamic range is about 67dB and 62dB for the LF and FLF filters respectively, and power consumption is about 67mW at 30MHz for both filters. Less than 0.5dB passband ripple is achieved for both filters; 65dB and 50dB stopband attenuations are obtained for MLF LF and FLF configurations, respectively.