Low Power Fully Differential CMOS First Order All Pass Filter with 0.2- 4.8Hz Variable Pole Frequency

A fully differential and fully integrated low voltage all pass filter operated in the sub-threshold region with variable pole frequency designed in CMOS 130nm technology is presented in this paper. It has only 0.09dB passband ripple. It works with ±200mV DC supplies and dissipates 0.7µW quiescent power. The Miller multiplication effect and quasi floating gate transistors make it possible to achieve a time constant in the range of seconds without consuming excessive Si area. The proposed filter's pole frequency can be varied from 242mHz to 4.8Hz by changing the Miller amplifier's gain. Simulation results in 130nm CMOS technology validate the proposed circuit.