New CMOS Realization of Voltage Differencing Buffered Amplifier and Its Biquad Filter Applications

Abstract

In this paper, new biquad filter configuration using a recently introduced active element, namely Voltage Differencing Buffered Amplifier (VDBA), is proposed. This block has high impedance input terminals and low impedance output terminal, providing advantages at voltage mode circuits. Besides, VDBA has a transconductance gain, thus the proposed circuits can be employed without using any external resistors. Two new voltage-mode biquad filter configurations are presented for VDBA application. Each proposed filter employs two active elements and two or three passive components. Filters, having three inputs and single output, can realize voltage-mode low-pass, band-pass, high-pass, band-stop, and allpass filters. The biquad filters have low output impedances that is necessary for cascadability for voltage mode circuits, and no critical component matching conditions are required. For the second biquad, quality factor can be adjusted via resistor independently of the natural frequency. Simulation results are given too, confirming the theoretical analysis. The proposed biquad filters are simulated using TSMC CMOS 0.35 mu m technology. LTSPICE simulations of the proposed circuits give results that agree well with the theoretical analysis.