Electronically Tunable Current-mode High-order Ladder Low-pass Filters Based on CMOS Technology

This paper describes the design of current mode low-pass ladder filters based on CMOS technology. The filters are derived from passive RLC ladder filter prototypes using new CMOS lossy and lossless integrators. The all-pole and Elliptic approximations are used in the proposed low-pass filter realizations. The proposed two types of filter can be electronically tuned between 10 kHz and 100 MHz through bias current from 0.03 mu A to 300 mu A. The proposed filters use 1.5 V power supply with 3 mW power consumption at 300 mu A bias current. The proposed filters are resistorless, use grounded capacitors and are suitable for further integration. The total harmonic distortion ( THD) of the low-pass filters is less than 1% over the operating frequency range. PSPICE simulation results, obtained by using TSMC 0.18 mu m technology, confirm the presented theory.