Fully integrated active filter design for ultra low frequency application

This paper presents a new active capacitance multiplier circuit, by which it is possible to obtain higher capacitance values. The capacitance multiplier is based on cascaded current multiplier cells (CMC). The proposed circuit is preferred for low power low voltage applications since it is based on CMOS inverters and op-amps. The capacitance multiplier is employed in the design of a first order LPF with a cutoff frequency as low as 135 Hz using an on-chip capacitor of 1 pF only. The circuit is simulated in CMOS 0.13 mu m process. Simulation results show close agreement with the analytical calculations.