Programmable Universal Filters Using Current Conveyor Transconductance Amplifiers

This paper presents new programmable universal biquadratic filters using current conveyor transconductance amplifiers (CCTAs) by which both voltage-and current-mode filters can be obtained. The proposed filters use second-generation current conveyor (CCII) which is the first stage of CCTA to operate as current conveyor analog switch (CCAS) and this CCAS will be used to program the filtering functions such as low-pass, high-pass, band-pass, band-stop and all-pass fillters. Unlike previous universal filters, the filtering functions of the proposed filters can be programmed using the bias currents of CCTAs without changing any input and output connections. The natural frequency and quality factor of all filtering functions can be controlled electronically and orthogonally using the bias currents of transconductance amplifiers. Also gain response of all transfer functions can be adjusted. The active and passive sensitivities of the filters are low. The proposed programmable filters have been simulated using 0.18 mu m CMOS process from TSMC. PSPICE simulation results are included to confirm workability of the proposed circuits.