Novel current-mode and voltage-mode universal biquad filters using single CFTA

Abstract

This paper presents two novel electronically tunable universal filter configurations employing a single new active device, namely the current follower transconductance amplifier (CFTA). The first proposed current-mode universal filter with single input and three outputs consists of one CFTA, one virtually grounded resistor and two grounded capacitors. It can simultaneously realize low-pass, band-pass and high-pass responses with no need to impose component choice. A new three-input single-output universal voltage-mode biquad using one CFTA, two resistors and two capacitors is also proposed as a second proposed circuit. The latter circuit can be configured to realize all the five standard biquadratic filter functions; low-pass, band-pass, high-pass, band-stop and all-pass, without changing the circuit configuration. Both two universal biquad filters also offer the advantage features of the use of minimum number of passive components, and independent electronic tuning of the important filter parameters (<i>ω_o</i> and BW), as well as low active and passive sensitivities. To demonstrate the performances of the proposed filters and verify the theory, PSPICE simulations are accomplished.