Nonlinear Applications of CCs - Current Conveyors: Variants, Applications and Hardware Implementations - page 240

Some sample experimental results from [ 23 ] based upon the implementation of
the circuit using AD844 for CCII+, with passive component values as: R 1 ¼ 280 ʩ

and C 1 ¼ 1 uF are shown in Fig. 8.28d, e . The frequency of the output waveform

was found to be changeable through C 1 and/or R 1 while the amplitudes can be
varied through C 2 and/or R 3 .
Interested readers are referred to [ 28 , 42 - 44 ] for some other contributions on this
topic such as, design of low-power relaxation oscillators [ 28 ], the design of Schmitt
triggers with controllable hysteresis [ 42 ], tunable CC-based relaxation oscillator
[ 43 ] and square wave generator with voltage-controlled frequency [ 44 ].

8.10 Chaotic Oscillators Using CCs

Chaos generators have received considerable interest in recent literature because of
their possible applications in secure communication and signal encryption. While
most earlier implementations of chaotic circuits such as Chua s oscillator were

based upon traditional op-amps, subsequently there has been considerable interest
in realizing inductor-less chaotic oscillators using other building blocks such as
CCIIs and CFOAs because of the several advantages provided by such
implementations such as: canonic realizability of inductor simulation using a
minimum possible number of external passive components without requiring any
component matching, availability of the state variables such as inductive current
through the Z terminals of the CCIIs and CFOAs, relatively high frequency
applicability and ease of realizing the required simulated inductors and non-linear
negative resistors etc. As a consequence, a variety of chaotic oscillators using CCIIs
have been advanced in the literature. In the following we discuss some prominent
CCII-based chaotic oscillators.
Two simple chaotic oscillators obtained by simple modification of the classical
Wien bridge oscillator using CCII were advanced by Elwakil and Soliman in
[ 13 ]. One of these circuits is shown here in Fig. 8.29 . The additional part here is
the capacitor C 3 and the JFET-based resistor in series with the capacitor C 1 .
A dimensionless state-space description of this circuit is given by the following
equations:

'

dX

dt ¼ 2

ð Z X Þ ð Z X Þ 1

ð 8 : 41 Þ

1 ð Z X Þ > 1

dY
dt ¼

aY bZ ð 8 : 42 Þ

dZ
dt ¼

c dY

dX
dt þ dt

dY eZ ð 8 : 43 Þ