A CFOA-Based Voltage-Mode Multifunction Biquadratic Filter and a Quadrature Oscillator Using the CFOA-Based Biquadratic Filter

Abstract

This paper proposes a new high-input impedance current feedback operational amplifier (CFOA)-based voltage-mode multifunction biquadratic filter and a voltage-mode quadrature oscillator using the proposed high-input impedance CFOA-based biquadratic filter. The proposed high-input impedance CFOA-based voltage-mode multifunction biquadratic filter uses three CFOAs, three resistors, and two grounded capacitors with two inputs and three outputs. The filter can simultaneously realize non-inverting low-pass, non-inverting band-pass, and non-inverting band-reject filtering functions at the high-input impedance terminal while the inverting band-pass and non-inverting high-pass filtering functions can also be obtained by applying another high-input impedance terminal. The filter offers orthogonal control of resonance angular frequency and quality factor. The proposed high-input impedance CFOA-based voltage-mode multifunction biquadratic filter can be used to implement a voltage-mode quadrature oscillator with an independently controlled the frequency of oscillator and the condition of oscillation. The OrCAD PSpice simulation and experimental results of the commercially available integrated circuit, AD844AN, are used to confirm the characteristics of the proposed filter and oscillator.

Analytical Synthesis of High-Pass, Band-Pass and Low-Pass Biquadratic Filters and its Quadrature Oscillator Application Using Current-Feedback Operational Amplifiers

“…CFOA active components have been recognized by circuit design researchers and have drawn great attention in realizing filters and oscillators. Assuming ideal conditions, the input-output relationship of a CFOA is described by IY = 0, VX = VY, IZ = IX and VO = VZ [45]. The block diagram of Fig.…”

“…The measured results show that the phase noise is less than −40.77 dBc/Hz at 1 kHz offset. (45) where L(Δω) is the phase noise at the offset frequency to the carrier, Δω is the offset frequency relative to the carrier, ωo is the oscillation frequency, and PDC is the power consumption. According to (45), the FOM of the CFOAbased oscillator chip cell is 90.9 dBc/Hz.…”

“…However, the characteristic parameters of resonance angular frequency (ωo) and quality factor (Q) of these two filters cannot be controlled independently. In [45], a CFOA-based VM biquadratic filter is proposed, which includes three CFOAs, two grounded capacitors and three resistors. The filter can simultaneously obtain three transfer functions, but the characteristic parameters of ωo and Q are not independently controllable.…”

Enhancing Q-Factor in a Biquadratic Bandpass Filter Implemented with Opamps

“…In this manner, Equation (2) can be updated to (11), and then the symbolic transfer function can be expressed by Equation 12, from which one can evaluate the angular frequency ω o and Q, as given by Equations (13) and (14).…”

“…Fortunately, if one designs an opamp-RC filter with stable and high Q factor, such a topology can be transformed to a Gm-C one that can work in voltage-mode or current-mode, as shown in the work by the authors of [10]. For instance, some recent efforts on designing BPF responses work in current-mode, like in works by the authors of [11,12]; in voltage-mode, like in works by the authors of [13,14]; or apply modern active devices, like in works by the authors of [15][16][17]. Also, other efforts are oriented to provide reconfigurability and tune-ability at the same time and designing fractional-order circuits as in the work by the authors of [18].…”