Design of Gm-C low-pass filter with a low corner frequency

摘要

A fully differential third-order Butterworth low-pass filter by using Gm-C circuits is designed and presented for low-frequency applications. Its corner frequency can be changed from 0.5 Hz to 5 Hz by tuning its bias current. Moreover, the relationship between the corner frequency and bias current is very linear. According to the simulation results, the total harmonic distortion (THD) is lower than −60dB, when the differential peak-to-peak input voltage is 2V. The filter is designed and implemented by using the TSMC 0.35µm CMOS process and the supply voltage is 3.3V. The power consumption is lower than 85µW.