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Voltage Tunable Allpass Filters Using MMCC
Sagarika Das, P. Venkateswaran and R. Nandi

The realization of electronically tunable allpass phase-selective filters using the new Multiplication Mode Current Conveyor (MMCC) device is proposed; both first and second order implementations are presented. Electronic tunability is obtained by applying the control voltage directly to the control terminal of the device without necessitating any elaborate current sensing circuitry. The second order function is designed by using a high quality shunt-LC resonator based on a new synthetic lossless-L derived from a Differential Voltage Current Conveyor Transconductance Amplifier (DVCCTA) device wherein both capacitors are grounded. Both these active devices were implemented for the proposed work by readily available current feedback amplifier (CFA) elements. The configurations have been thoroughly analyzed with respect to device imperfections and it has been shown that the active sensitivities are quite low. Experimental results had been verified satisfactorily using hardware test and by PSPICE simulation; desired electronic tunability of the output-phase were obtained upto 300KHz whereby the unity-transmission gain remained unaltered.

Keywords: Allpass filter, Electronically tunable filter, Phase selective filter, Multiplication Mode Current Conveyor (MMCC)

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