Single-input three-output electronically tunable universal current-mode filter using current follower transconductance amplifiers

In this paper, an electronically tunable universal filter configuration with single input and three outputs (SITO) employing a recently introduced active device namely current follower transconductance amplifier (CFTA) is described. The proposed filter is composed of four CFTAs and two grounded capacitors, and is capable of realizing all the standard functions of the universal filter without requiring any component matching criterions and any extra active components. It exhibits low-input and high-output impedances, which is highly desirable for cascading in current-mode. It also offers the advantage feature of an independent electronic adjustment of the natural angular frequency (ωo) and the quality factor (Q) by means of tuning the external bias currents. Moreover, a high Q-value filter can be obtained by simply adjusting the appropriate ratio of bias currents. The analysis of active and passive sensitivities is shown to be low. In order to demonstrate the performance of the proposed circuit, PSPICE simulation results are provided.