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Voltage-Mode Multifunction Biquad Filter and Its Application as Fully-Uncoupled Quadrature Oscillator Based on
San-Fu Wang1, Hua-Pin Chen2, Yitsen Ku3
1Department of Electronic Engineering, National Chin-Yi University of Technology, Taiping, Taichung 41170, Taiwan.
Sensors (Basel, Switzerland)
|December 3, 2020
Summary
This study presents a new voltage-mode multifunction biquad filter and quadrature oscillator using current-feedback operational amplifiers. These circuits offer independent control of parameters and solve amplitude instability issues, validated by simulations and experiments.
Area of Science:
- Electronics Engineering
- Analog Circuit Design
Background:
- Existing voltage-mode (VM) multifunction biquad filters often lack independent control over pole frequency (ωo) and quality factor (Q).
- Quadrature oscillators (QOs) frequently face challenges with amplitude instability and coupled control parameters.
- Current-feedback operational amplifiers (CFOAs) offer potential for high-performance analog filter and oscillator designs.
Purpose of the Study:
- To introduce a novel VM multifunction biquad filter utilizing CFOAs with independent ωo and Q control.
- To develop a VM fully-uncoupled QO derived from the proposed biquad filter topology.
- To address and resolve amplitude instability in VM QOs and ensure constant amplitude ratios for quadrature outputs.
Main Methods:
- Design of a VM multifunction biquad filter employing three CFOAs, four resistors, and two grounded capacitors.
- Modification of the biquad filter topology to create a VM fully-uncoupled QO.
- Independent adjustment of oscillation condition and frequency using distinct resistor sets.
- PSpice simulations and experimental verification of circuit performance.
Main Results:
- The proposed VM biquad filter simultaneously provides low-pass, band-pass, and band-reject functions with high input impedance.
- Independent control of ωo and Q is achieved by varying specific resistors.
- The derived VM QO exhibits fully-uncoupled control of oscillation parameters and solves amplitude instability.
- Constant amplitude ratios for quadrature sinusoidal outputs are demonstrated.
Conclusions:
- The proposed VM multifunction biquad filter and VM fully-uncoupled QO offer significant advantages in independent parameter control and stability.
- The circuits are suitable for cascading in VM applications due to high input impedance.
- Simulation and experimental results validate the theoretical analysis and practical implementation of the proposed circuits.
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