Hardware Reference
In-Depth Information
a
b
R
1
x
I
0
R
2
C
1
CCI
z
I
0
x
V
01
y
CCI
R
1
z
B
1
C
2
B
1
B
2
y
V
02
R
3
V
01
C
2
C
1
R
3
R
2
Fig. 7.19 SRCOs proposed by Senani and Gupta [
38
] (The circuit of Fig.
7.19b
has also been
derived
independently
in [
42
] by the approach adopted therein is quite different than the one
employed in [
38
])
7.7 SRCOs with Grounded Capacitors and Reduced Effect
of Parasitic Impedances of CCIIs
Out of the three circuits derived systematically by Martinez et al. [
35
], through a
formulation based upon two integrator loop biquadratic general structure, the two
circuits which appear to be the better than the remaining ones are shown here in
Fig.
7.20
.
A notable feature of these circuits is that the parasitic X-terminal input resistance
R
x
of all the current conveyors can be absorbed in the external resistances
connected to terminal-X of the CCs namely, R
A
and R
2
in the circuit of
Fig.
7.20a and R
A,
R
1
and R
2
in case of circuit of Fig.
7.20b
. On the other hand,
the Z-port parasitic capacitance of the CCs can be merged in the external capacitors
C
1
and C
2
as they are connected from the Z-terminals of the CCs only. Thus, it is
expected that the circuits would exhibit good high frequency performance.
Experimental results using CCIIs implemented from AD844 confirm that these
circuits can be satisfactorily employed to generate oscillations up to 10 MHz. It has
been possible to obtain signals from 40 to 400 KHz with average peak-to-peak
amplitude of 15 V and THD of less than 1 %.
It is also interesting to note that the circuit of Fig.
7.20a
has an additional
advantage of providing an explicit current mode output from the Z-terminal of
the first CCII+ while the voltage output can be taped from any appropriate node.
7.8 Fully-Uncoupled Oscillators
Fully-uncoupled oscillators are those in which the components which control the
condition of oscillation do not appear in the expression for frequency of oscillation
and on the other hand, the components appearing in FO do not appear in CO.
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