Two Op Amp oscillator using Deboo integrator 
The circuit shown in Fig. 3 is the well known quadrature
oscillator  based on using Deboo noninverting integrator
The quadrature oscillator circuit given in Fig. 3 is
realizable using two CFOA as shown in Fig. 6(a).
This circuit was reported in [11, 13] without any reference to the
Op Amp equivalent circuit of Fig. 3. .
The natural sequence of generation in this paper is to obtain the
circuit of Fig. 6(b) from the circuit of Fig. 6(a) by
changing the signs of G1, G2 and
G3 in Eq. 16 which represents the circuits in
Fig. 3 as well as the circuit in Fig. 6(a).
This circuit has the same condition of oscillation as the circuits
of Figs. 3 and 6(a) and given by Eq. 14.
It should be noted however that the start up condition of
oscillation is adjusted by taking R1 slightly larger
than R3 which is opposite to the case of the two
equivalent circuits of Figs. 3 and 6(a) in which R1
is adjusted to be slightly smaller than R3..
Simulation results for the circuit of Fig. 3 using two
μA741 Op Amps biased with 12 and −12 V and taking
R1 = R2 = R3 = R = 10 k Ω,
and two equal capacitors of 1 nF each.
Simulation results of the oscillator of Fig. 3
The CFOA circuit of Fig. 6(a) is equivalent to and has
identical NAM equation to the Op Amp circuit of Fig. 3.The NAM
equation of the CFOA circuit of Fig. 6(b) is obtained from
that of the circuit of Fig. 6(a) by interchange of the signs
of the three G terms but has no equivalent Op Amp circuit.
Spice simulation results are included for the circuits of
Figs. 2(c) and 3..
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