Electronically Adjustable Emulator of the Fractional-Order Capacitor

This paper presents a design of the controllable emulator of the FOC (Fractional-Order Capacitor) and its application. The circuit is based on 5th-order RC topology (type Foster I), where the passive elements in the topology are replaced by electronically adjustable components. The proposed emulator is based on OTA (Operational Transconductance Amplifier) and VDCC (Voltage Differencing Current Conveyor). The electronically controllable resistors are implemented by OTAs. The electronically tunable capacitors are implemented using capacitance multipliers, which employ VDCCs. The proposed structure provides the electronic control of the order and electronic shifting of the frequency band of the approximation validity. The proposed FOC emulator is also used for fractional-order filter design. The proposed circuits are verified using PSpice simulations.