Fully integrated electronically tunable universal biquad filter operating in current-mode

A new current-mode universal filter structure consisting of three current-follower transconductance amplifiers (CFTAs) and two grounded capacitors is described in this paper. By the proper selection of three current input (s), it can realize all the five standard filtering responses namely, low pass (LP), band pass (BP), high pass (HP), band reject (BR), and all pass (AP) at single high impedance current output terminal. Thus, the proposed biquad structure is a multi-input single-output type filter configuration. It offers number of remarkable features such as wide range of orthogonal electronic tunability of filter parameters, capability to realize various filtering responses without using inverted current input signal(s) and low sensitivities with respect to active and passive components. The circuit performance is examined through P-SPICE simulation on ORCAD tools.