A voltage-mode universal biquadratic filter using a differential voltage current conveyor (DVCC), two capacitors, and two resistors is presented. The proposed circuit has four input terminals and three output terminals and can realize all the standard filter functions, which are lowpass, bandpass, highpass, notch, and allpass filters, without changing the circuit topology. Three simultaneous output filter responses can be obtained from some derived filter types. The proposed circuit employs only one DVCC that simplifies the configuration. 1. Introduction Recently, there is a growing interest in designing current-conveyor- (CC-) or current-feedback-amplifier- (CFA-) based active filters. This is attributed to their high signal bandwidths, greater linearity, and larger dynamic range than OPAMP-based ones [1]. Note that a CFA is equivalent to a plus-type second-generation current conveyor (CCII) with a voltage follower [2]. Active filters are so widely used in electronic systems, such as telecommunications, radar, consumer electronics, instrumentation systems, and military ordnance, [1, 3]. Many voltage-mode universal biquadratic filters with multi-inputs were proposed [4–10]. From the different combinations of injection of input voltage signals, voltage-mode lowpass, bandpass, highpass, notch, and allpass filters can be obtained without changing the circuit topology. However, these circuits require at least two active components. Moreover, the universal biquadratic circuits in [4, 7–9] require one more active component for the unity-gain inverting input in the allpass realizations. In 2002, Horng et al. proposed a universal biquad with four inputs using three resistors, two capacitors, and one CFA [11]. However, it still requires one more active component for the unity-gain inverting input in the allpass realization. Two voltage-mode universal biquads each with three inputs using two resistors, two capacitors, and one CCII were presented in [12, 13]. However, each of these two circuits requires one more active component for amplifying the input signal in the notch and allpass realizations. A voltage-mode universal biquadratic filter using single plus-type CCII (CCII+), two resistors, and two capacitors was presented in [14]. However, only two standard filter types can be obtained simultaneously in the same circuit. In this paper, a voltage-mode universal biquadratic filter circuit that has four input terminals and three output terminals is presented. It can realize all the standard filter functions, which is, lowpass, bandpass, highpass, notch, and
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