Abstract
This research introduces a new multifunction biquad filter based on voltage mode (VM) current-feedback operational amplifier (CFOA) and a fully uncoupled quadrature oscillator (QO) based on the proposed VM multifunction biquad filter. The proposed VM multifunction biquad filter has high impedance to the input voltage signal, and uses three CFOAs as active components, while using four resistors and two grounded capacitors as passive components. The VM CFOA-based multifunction biquad filter realizes band-reject, band-pass, and low-pass transfer functions at high-input impedance node simultaneously, which has the feature of easy cascading in VM operation without the need for additional voltage buffers. Additionally, the filter control factor parameter pole frequency (ωo) and quality factor (Q) of the proposed VM multifunction biquad filter can be independently set by varying different resistors. By slightly modifying the VM multifunction biquad filter topology, a VM fully-uncoupled QO is easily obtained. The difference from the previous VM CFOA-based multifunction biquad filter is that the proposed VM CFOA-based multifunction biquad filter can be independently controlled by the filter control factor parameters, ωo and Q. The proposed VM CFOA-based multifunction biquad filter can be transformed into a VM QO with fully-uncoupled adjustable of the oscillation condition and the oscillation frequency. The oscillation condition and the oscillation frequency can be fully-uncoupled and controlled by varying two sets of completely different resistors. The proposed VM fully-uncoupled QO solves the amplitude instability. The constant amplitude ratio of two quadrature sinusoidal waveforms can be realized when tuning FO. PSpice simulation and experimental results prove the performances of the proposed VM multifunction filter and VM fully-uncoupled QO. Simulation and experimental results confirm the theoretical analysis of the proposed circuits.
Highlights
Voltage-mode (VM) analog active filters and oscillators using different active components have received extensive attention
This method has the into account the parasitic impedances of non-ideal current-feedback operational amplifier (CFOA), the biquad filter presented in Figure 2 is characteristic that the parasitic capacitance, CZ, is directly incorporated into Z terminal of CFOA as a modified to Figure 3
The paper proposes an independently tunable VM multifunction biquad filter with high-input impedance and a VM fully-uncoupled quadrature oscillator (QO) realized by the proposed VM multifunction biquad filter
Summary
Voltage-mode (VM) analog active filters and oscillators using different active components have received extensive attention. CFOA-based VM multifunction biquad filter are follows: (i) use only three CFOAs, (ii) use only two grounded capacitors, (iii) realize three standard filter transfer functions with one input and three outputs at the same time, (iv) high-input impedance, (v) the input parasitic resistances of the X ports of the CFOAs can be accommodated in an external resistors, (vi) independent control of the filter control factor parameters ωo and Q, and (vii) transformed into a VM QO with fully-uncoupled adjustable of CO and FO. Note: (i) Use up to three CFOAs; (ii) use only two grounded capacitors; (iii) realize three standard filter transfer functions simultaneously; (iv) high-input impedance; (v) CFOA’s X ports input parasitic resistances can be accommodated in an external resistors; (vi) independent control of the filter control factor parameters pole frequency and quality factor; (vii) transformed into a voltage-mode QO with fully-uncoupled adjustable of the condition of oscillation and the frequency of oscillation; Simul.: simulation result; Meas.: measurement result; ICs: integrated circuits; N/A—not available or not tested.
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