Cascadable Current-Controlled Current-Mode Multifunction Filter Using CDTAs

The cascadable current-controlled current-mode multifunction filter with three inputs and one output using current differencing transconductance amplifiers (CDTAs) as active components is presented. The proposed configuration comprising only three CDTAs and two grounded capacitors provides low-input and high-output impedances, which is advantageous from an integration point of view and is important for easy cascading in the current-mode operations. By properly joining the input and output terminals, the circuit can simultaneously realize all the standard filter functions, namely lowpass (LP), bandpass (BP), highpass (HP), bandstop (BS) and allpass (AP), without any component matching conditions. The natural angular frequency (omega_o) and the bandwidth (omega_o/IQ) of the proposed filters can be electronically controlled, thanks to the tunability properties of the CDTAs. All the passive and active sensitivities are low. SPICE simulation results are included to confirm the theory.