Single-resistance-controlled quadrature oscillator and universal biquad filter using CFOAs

Voltage-mode universal biquadratic filter and quadrature oscillator using CFAs

“…o , which the circuit of Fig. 3 in [9] does not provide. Another example in the oscillator structure, both two capacitors of the proposed circuit are grounded, but one capacitor in the circuit of Fig.…”

“…o and Q, cannot be controlled orthogonally. Third, a voltage-mode single-resistance-controlled sinusoidal quadrature oscillator and a voltage-mode universal biquadratic filter based on two CFAs, two/three resistors, and two capacitors has been proposed in 2009 [9]. Nevertheless, the voltage-mode universal filter and the quadrature oscillator need to be realized in the different configuration.…”

“…Another example in the oscillator structure, both two capacitors of the proposed circuit are grounded, but one capacitor in the circuit of Fig. 2 in [9] is floating. Also, the proposed circuit allows independent control of the oscillation condition and oscillation frequency, which the circuit in [10] does not allow.…”

“…Recently, many CFA based voltage-mode universal biquadratic filters [3,4,5,6,7,8] and quadrature oscillators [9,10,11,12,13] have been reported in some technical literatures. However, all of them only provide one function, either a universal biquadratic filter [3,4,5,6,7,8] or a quadrature oscillator [9,10,11,12,13]. For example, a versatile voltage-mode biquadratic filter with four inputs and three outputs based on three CFAs, three resistors and two capacitors has been proposed in 2005 [7].…”

Quadrature oscillators using two CFOAs and four passive components

“…In the last two decades on the realization of voltage-mode oscillators, an application of current-feedback operational amplifier (CFOA) [3,4,5,6,7,8,9,10,11,12], double current controlled current feedback amplifier (DCC-CFA) [13], currentcontrolled current feedback amplifier (CC-CFA) [14], differential voltage current conveyor transconductance amplifier (DVCCTA) [15], differential-input buffered and transconductance amplifier (DBTA) [16], and second-generation conveyor (CCII) [17] have received considerable attention. Moreover, the four terminal CFOA, particularly the commercial available integrated circuit (IC) type AD844 providing an accessible compensation pin, has received prominent attention [3,4,5,6,7,8,9,10,11,12]. Although a number of single CFOA-based oscillators have been proposed in the literature [4,5,6,7], none of them employ both grounded capacitors.…”