Voltage-Mode Biquad Filter Using Four OTAs and Its Application in Quadrature Oscillator with Noninteractive Control of the Oscillation Condition and Frequency

Abstract

This paper presents an independently tunable, four-input, three-output, voltage-mode (VM) biquad filter consisting of four operational transconductance amplifiers (OTAs) and two grounded capacitors. The proposed circuit can simultaneously realize three basic biquad filtering functions for single input and three outputs. All five standard biquad filtering functions can be implemented with four inputs and single output by appropriate application of input voltage signals. The developed biquad filter with high input impedances enables noninteractive control of natural angular frequency and quality factor. By slightly modifying the proposed biquad filter, the VM quadrature sinusoidal oscillator with noninteractive control for the oscillation condition and the oscillation frequency has been achieved. Simulation and experimental results are used to validate theoretical predictions.