Two new voltage-mode universal biquadratic filters each with three input signals and one output signal are presented. Each proposed universal biquadratic filter is composed of only two CCIIs, two capacitors and two resistors and can realize all the standard filter functions, that is, highpass, bandpass, lowpass, notch and allpass filters (one more active device is needed for the realization of allpass filter). The proposed circuits have good sensitivities performance and have no requirements for component-matching conditions.

A three inputs and single output voltage-mode universal biquadratic filter using only two operational transconductance amplifiers (OTAs) and two capacitors is presented. The new circuits offer several advantages, such as employing the minimum number of active and passive components (two OTAs and two capacitors), the versatility to synthesize highpass, bandpass, lowpass, notch and allpass responses without component matching conditions, high input impedance for bandpass and lowpass filter realizations and good sensitivities performance.

A voltage-mode universal biquadratic filter using single current-feedback amplifier (CFA), two capacitors and three resistors is presented. The new circuit has four inputs and one output and can realize all the standard filter functions, that is, lowpass, bandpass, highpass, notch and allpass filters, without changing the circuit topology. The use of only one current-feedback amplifier simplifiers the configuration.