CMOS realization of voltage differencing gain amplifier (VDGA) and its application to biquad filter

A circuit realization of the voltage differencing gain amplifier (VDGA) using only tunable transconductance cells is described in this paper. The newly defined element is conceptually a combination of the voltage differencing unit and the current-controlled voltage amplifier. The advantage feature of the proposed element is that the important transfer characteristics are electronically tunable by means of external bias currents. As application example, the resistorless realization of voltage-mode biquad filter based on the proposed VDGA is also introduced. PSPICE simulation results of the proposed circuit and its application are given to confirm the theoretical analysis.