Design and optimization of MOSFET-capacitor filters using CMOS current conveyors

A CMOS current conveyor is proposed, and an MOSFET-capacitor integrator consisting of the CMOS current conveyor, MOSFETs biased in the triode region, capacitors, and a unity-gain buffer is presented. Based on this integrator, high-frequency integrated filters can be constructed. However, the design of such filters is complicated by the fact that the effective mobility of each device may vary and the basic building blocks (i.e. operational amplifiers or CMOS current conveyors) are not ideal. An optimization program has been developed to automate the design of this kind of filter. The program iteratively adjusts the W/L ratios and capacitance values through interfacing with SPICE to achieve the desired filtering performance. Simulation results on a six-order bandpass ladder filter with center frequency at 460 kHz, 0.5-dB ripple in the passband, and a bandwidth of 120 kHz are presented.<<ETX>>