Cascadable Current-Controlled Current-Mode Universal Filters Using CDTAs and Grounded Capacitors
This paper presents two cascadable current-controlled current-mode universal filters using current differencing transconductance amplifiers (CDTAs) as active components. The first configuration has three inputs and a single output, and the second one has two inputs and three outputs. Both filter configurations comprising only three CDTAs and two grounded capacitors exhibit 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 filters 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 (ωo) and the bandwidth (ωo/Q) 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.
Keywords: Current differencing transconductance amplifier (CDTA), current-mode filters.