A 6th order zero capacitor spread 1MHz – 10MHz tunable CMOS active-RC low pass filter with fast tuning scheme

A 6^th order fully differential CMOS active-RC inverse-Chebyshev low pass filter with zero capacitor spread is presented in this paper. It provides inverse-Chebyshev response with tunable cutoff frequency from 1MHz to 10MHz by regulating a resistor array. Transmission zero capacitors are replaced by resistors to eliminate the large capacitor spread also in order to reduce the area and mismatch. Modified bandwidth extended op-amp with push-pull output stage is employed to meet the power consumption and bandwidth requirements. A fast tuning circuit using successive approximation register (SAR) controller is adopted to compensate the process voltage temperatue (PVT) variations by tuning a capacitor array. Implemented in 0.13um CMOS technology, the filter draws 6.3mA from a 1.5V power supply. Simulation results show that the inband input-referred noise is 60nV/sqrt(Hz), inband 1dB gain compression point is larger than 13dBm and inband total harmonic distortion (THD) is less than −80dB with 2V differential peak-peak (2Vppd) input signal.