CMOS First-Order All-Pass Filter With 2-Hz Pole Frequency

A CMOS fully integrated all-pass filter with an extremely low pole frequency of 2 Hz is introduced in this paper. It has 0.08-dB passband ripple and 0.029-mm
²
Si area. It has 0.38-mW power consumption in strong inversion with ±0.6-V power supplies. In subthreshold, it has 0.64-μW quiescent power and operates with ±200-mV dc supplies. Miller multiplication is used to obtain a large equivalent capacitor without excessive Si area. By varying the gain of the Miller amplifier, the pole frequency can be varied from 2 to 48 Hz. Experimental and simulation results of a test chip prototype in 130-nm CMOS technology validate the proposed circuit.