Design of Gain and Bandwidth Configurable Elliptic Low-pass Filter

This paper presents a gain and bandwidth configurable elliptic low-pass filter(LPF). Three Tow-Thomas biquads are cascaded to achieve the 6-order low-pass filter. Position of zero and pole pairs, quality factor(Q) and gain of each biquads are configurable to achieve high linearity and low noise figure. The LPF is designed in 0.18-μm CMOS process, and the gain varies from 0 dB to 54 dB with 6 dB a step and the cut-off frequency varies from 0.5 MHz to 4 MHz. Simulation results show that the in-band ripples are controlled within ±0.15 dB at all gain mode. The attenuation of stopband is up to 60 dB. The in band IIP3 > 39 dBm and out band IIP3 > 45 dBm. The total power of the filter is 17.4 mW.