Ever since the introduction of the voltage differencing transconductance amplifier (VDTA) by Biolek et.al. [1], this active device has been successfully used for realizing sinusoidal oscillator and filter circuits [2–11]. Accordingly, a number of active filter circuits using VDTAs as active elements and passive elements have been reported in the literature [3–11]. However, most of the previously reported circuits were based on voltage-mode operations. At present, the current-mode approach is of great interest with the recent popularity of current-mode circuits. Therefore, the design of current-mode active filters is attractive in analog signal processing applications. Moreover,from the poin tof view of the advantages of simplicity,cost reduction, low power consumption and space saving, it is beneficial to design the active filters using a single active component and keeping the number of passive components to a minimum. In this paper, a compact current-mode electronically tunable universal biquadratic filter with three inputs and a single output using one VDTA is presented. The circuit employs only two grounded capacitors as passive components, without the employment of external passive resistors. According to the proper selection of the input signals, all the five basic biquadratic filtering functions, namely lowpass(LP),bandpass(BP),highpass(HP),bandstop(BS)andallpass (AP), can be realized from the presented circuit configuration. The natural angular frequency (ω0) and the quality factor (Q) of the