RESUMEN
This paper presents four new designs for a first-order voltage-mode (VM) all-pass filter (APF) circuit based on two single-output positive differential voltage current conveyors (DVCCs). The first two proposed VMAPFs with unity-gain, high-input (HI) impedance and low-output (LO) impedance use two DVCCs, a grounded capacitor, and a grounded resistor. The last two proposed first-order VMAPFs with HI impedance and variable-gain control are two resistors added to each of the first two VMAPFs. The last two proposed first-order VMAPFs with variable-gain control use two DVCCs, one grounded capacitor, and three grounded resistors and provide HI impedances, so that VMAPFs can be directly cascaded to obtain high-order filters without additional voltage buffers. The four implementation circuits based only on grounded passive components are particularly applicable for integrated circuits (ICs). To confirm the cascading characteristics, an application example of a fully-uncoupled quadrature sinusoidal oscillator (FQSO) is also proposed. PSpice simulation results have confirmed the feasibility of the proposed structures. VMAPF and FQSO circuits are also constructed from commercial AD8130 and AD844 ICs, and their experimentally measured time and frequency responses are compared to theoretical values. The supply voltages for both the AD8130 and AD844 ICs were ±5 V. The measured power dissipation of the proposed first-order VMAPF and second-order FQSO circuits is 0.6 W. The measured input 1-dB compression point for the four VMAPFs is about 19 dB. The measured total harmonic distortion of the four VMAPFs is less than 0.67% when the input voltage reaches 2.5 Vpp. The calculated figures of merit for the four VMAPFs are 628.2 × 103, 603.06 × 103, 516.53 × 103, and 496.42 × 103, respectively.
RESUMEN
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.
RESUMEN
This paper presents a versatile tunable voltage-mode biquadratic filter with five inputs and three outputs. The proposed filter enjoys five single-ended output operational transconductance amplifiers (OTAs) and two grounded capacitors. The filter can be easily transformed into a quadrature oscillator. The filter with grounded capacitors is resistorless and electronically tunable. Either a voltage-mode five-input single-output biquadratic filter or a voltage-mode single-input three-output biquadratic filter can be operated by appropriate selecting input and output terminals. In the operation of five-input single-output biquadratic filter, the non-inverting lowpass, non-inverting bandpass, inverting bandpass, inverting highpass, non-inverting bandreject, inverting bandreject, and non-inverting allpass filtering responses can be realized by appropriately applying the input voltage signals. In the operation of single-input three-output biquadratic filter, the non-inverting/inverting lowpass, bandpass and bandreject filtering responses can be realized simultaneously. The circuit provides independent adjustment of the resonance angular frequency and quality factor, high-input impedance, and no inverting-type input voltage signals are imposed. The application in quadrature oscillator exhibits independent electronic tuning characteristic of the oscillation condition and the oscillation frequency. The theoretical analysis has been verified through OrCAD PSpice and furthermore by experimental measurements.