New gain controllable resistor-less current-mode first order allpass filter and its application

Abstract

New first order allpass filter (APF) in current mode, constructed from 2 CCCCTAs and grounded capacitor, is presented. The current gain and phase shift can be electronically/orthogonally controlled. Low input and high output impedances are achieved which make the circuit to be easily cascaded to the current-mode circuit without additional current buffers. The operation of the proposed filter has been verified through simulation results which confirm the theoretical analysis. The application example as current-mode quadrature oscillator with noninteractive current control for both of oscillation condition and oscillation frequency is included to show the usability of the proposed filter.