Electronically Tunable First-Order Filters and Dual-Mode Multiphase Oscillator

This paper introduces two novel circuits of first-order universal filter that comprise single multiple outputs dual-X current conveyor transconductance amplifier and one grounded capacitor only. The first circuit is of current-mode type, and second is of transadmittance-mode type. Both the circuits are suitable to modern IC technology and offer the feature of ease of cascadability. The proposed circuits do not need any passive component matching constraints. Moreover, the pole frequency of both the circuits is electronically tunable. The transadmittance-mode type circuit also provides an interesting feature of electronic and independent tuning of amplitudes of output currents without affecting the pole frequency. To check the applicability of the proposed circuit, a dual-mode multiphase oscillator is also derived from the proposed transadmittance-mode type filter. It provides two quadrature voltage outputs and four quadrature current outputs simultaneously. The oscillation frequency and condition of oscillation are orthogonally and electronically controllable. The non-ideal and parasitic analyses of all the proposed circuits are investigated, and HSPICE simulation results are depicted to confirm the proposed theory. Furthermore, transadmittance-mode type first-order universal filter is experimentally verified using commercially available ICs.