Current-mode variable current gain first-order allpass filter employing CFTAs

In this study, a current-mode first order allpass filter using current follower transconductance amplifiers (CFTAs) is proposed. The features of the circuit are that: the pole frequency, phase response and current gain can be electronically controlled via the input bias current: the circuit description is very simple, consisting of 2 CFTAs, 1 resistor and 1 grounded capacitor, without any component matching requirements. Consequently, the proposed circuit is very appropriate to further develop into an integrated circuit. Low input and high output impedances of the proposed configuration enable the circuit to be cascaded in current-mode without additional current buffers. The PSpice simulation results are depicted. The given results agree well with the theoretical anticipation.