New High Input Impedance Voltage-Mode Lowpass, Bandpass and Highpass Filter Using Current Feedback Amplifiers

Abstract

A new high input impedance filter employing three current feedback amplifiers (CFAs) and six passive elements, three of them are grounded, is presented. The proposed circuit offers the following advantages: simultaneous realization of lowpass (LP), bandpass (BP) and highpass (HP) filtering functions, employs two grounded capacitors, exhibits high input and low output impedances which permits easy cascade connection, low passive sensitivity figures and orthogonal control of resonance frequency (ωo) and bandwidth (ωo/Q). PSPICE simulation results are given to verify the theoretical calculations.

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

“…Moreover, the proposed CFOA-based voltage-mode multifunction biquadratic filter can be easily converted to a voltage-mode quadrature oscillator. Contrary to the previously reported CFOA-based voltage-mode multifunction biquadratic filters [26][27][28][29], the proposed filter meets all of the following advantages-(i) employs only three CFOAs, three resistors, and two grounded capacitors, (ii) can have simultaneously LP, BP, and BR filtering responses with a single input and three outputs by the use of only a single voltage input signal while the IBP and HP filtering responses can be realized by the use of another input voltage signal, (iii) has high-input impedance, (iv) has orthogonal control of ω o and Q, (v) has no capacitors bringing extra poles that degrade its high frequency performance, (vi) requires no inverting-type voltage input signals, and (vii) can transfer into a voltage-mode quadrature sinusoidal oscillator easily. The properties of the proposed filter and oscillator have been verified by PSpice simulations and furthermore by experimental measurements.…”

“…Reference [26] yes no no yes yes yes no Reference [27] no no yes yes yes yes no Reference [28] no yes yes yes yes yes no Reference [29] no no yes no no yes no Proposed yes yes yes yes yes yes yes…”

“…These proposed configurations can simultaneously realize low-pass, band-pass, and high-pass responses and have several other possible applications such as in crossover networks used in three-way high-fidelity loudspeakers, and phase-locked loop frequency modulation stereo demodulators [25]. Of particular interest here are the voltage-mode CFOA-based multifunction biquadratic filters [26][27][28][29]. Therefore, a voltage-mode non-inverting low-pass (LP), inverting band-pass (IBP), and non-inverting band-reject (BR) filter employing three CFOAs, three resistors, and two grounded capacitors has been proposed in the literature [26] but it does not offer high-input impedance.…”

“…A high-input impedance voltage-mode LP, IBP, HP, and BR filter employing four CFOAs, four resistors, and two grounded capacitors has been proposed in the literature [28] but it suffers from the drawback of using four CFOAs. A high-input impedance voltage-mode LP, BP, and HP filter employing three CFOAs, four resistors, and two grounded capacitors has been proposed in the literature [29] but it has a capacitor connected in series to the X port of the CFOA. Because the CFOA has a non-negligible output parasitic resistance on port X, R X , when the X port of CFOA is loaded by a capacitor, it leads to an improper transfer of functions.…”

“…Table 1. Comparison of the proposed circuit with previously CFOA-based multifunction biquadratic filters in the literature [26][27][28][29].…”