Second-generation voltage conveyor-based first-order all-pass filters and application to quadrature sinusoidal oscillator

This article describes 2 first-order voltage-mode all-pass filters (APFs) covering leading and lagging phases based on single capacitor and second-generation voltage conveyors (VCIIs). The proposed APFs comprise 2 VCIIs cooperating with 3 resistors and 1 capacitor. The phase angle of the output relative to input signals can be tuned by the single external resistor. Different from previously related works, they use only VCII+ which can be easily realized and less complicated for both integrated circuit architecture and off-the-shelf design. In addition, a 450 mV 1.98 µW VCII based on bulk-driven quasi-floating-gate MOS transistor was developed to be used in this work to achieve ultra low-voltage and low-power consumption. The proposed APFs offer a phase shifting function over a wide range of operating frequency. Its output also provides an accurate sinusoidal signal. The testing results obtained from Cadence Virtuoso System Design Platform simulation are disclosed to investigate different behaviors of the proposed APFs. In addition, the experimental setup using commercially available integrated circuits is shown. From the both results, it is found that they are agreed well with the mentioned anticipations. An application of the proposed APFs in quadrature sinusoidal oscillator is also depicted, it enjoys independent controllability of oscillation condition and oscillation frequency for a wide range of operating frequency with a precise quadrature output signal.