TISO Cascadable Current-Mode Multifunction Filter Employing Current Differencing Transconductance Amplifiers

A circuit realization of a current-mode multifunction filter with three inputs and one output employing current differencing transconductance amplifiers (CDTAs) as active components is presented in this paper. The proposed circuit employs only three CDTAs and two grounded capacitors and exhibit low-input and high-output impedances, which is very suitable for an integrated circuit implementation and easy cascading in the current-mode operations. By properly selecting the input current terminals, the proposed filter can realize all standard biquadratic functions, i.e., the lowpass (LP), highpass (HP), bandpass (BP), bandstop (BS) and allpass (AP) filtering functions without changing the circuit configuration. The natural frequency (omega₀ ) and the bandwidth (omega₀/Q) of the proposed filter can electronically be tuned by controlling the bias current of the CDTA. The filter also provides the low active and passive sensitivities. Simulation results with PSPICE are used to confirm the presented theory