## Caption

## Extracts from the Article What's this?

The circuit shown in Fig. 3 is the well known quadrature oscillator [1] based on using Deboo noninverting integrator [20].

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 G_{1}, G_{2} and
G_{3} 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 R_{1} slightly larger
than R_{3} which is opposite to the case of the two
equivalent circuits of Figs. 3 and 6(a) in which R_{1}
is adjusted to be slightly smaller than R_{3}..

Simulation results for the circuit of Fig. 3 using two
μA741 Op Amps biased with 12 and −12 V and taking
R_{1} = R_{2} = R_{3} = 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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