A low-distortion R-active-C lowpass filter for linear sensor applications

This paper presents a new low-frequency filter dedicated to the linear sensor applications. The CMOS active capacitor is bootstrapped by the embodiment of an operational amplifier (op-amp) based active capacitor into another op-amp based capacitor multiplier through using shared amplifier architecture for obtaining simplification. The proposed active capacitor forms a monolithic R-active-C low-pass filter (LPF) with a passive resistor. The simulation results, on the basis of AMS 0.35 μm CMOS models, have shown that a 2^nd order 200Hz LPF can achieve a Total Harmonic Distortion (THD) less than -53 dB at 2 V_pp and 40 Hz in a single 3.0 V supply, with a current consumption of 106 μA. Compared with the MOSFET-C and Gm-C counterparts, it significantly displays better linearity whilst offering high signal(Vpeak)/V_DD ratio in terms of efficiency in supply utilization.