Second Generation Controlled Current Conveyors (CCCII) and Their Applications - Current Conveyors: Variants, Applications and Hardware Implementations - page 280

LC, a shunt resistor along with a series LC, a shunt resistor with a series LC in
parallel with this and a shunt resistor along with a parallel LC in series arm.
For each of elements described in above four categories MCCCIIs based reali-
zations have been developed by simulating the node equations of the passive block
by MCCII based circuit in conjunction with grounded capacitor(s). For example the
MCCCII based realizations of the four single passive element blocks and realiza-
tions of single passive element along with source or load resistor have been shown
in Fig. 9.35 .
For the sake of brevity MCCCII based realizations of the remaining two classes
are not reproduced here, the interested reader may refer to [ 32 ] for their details.
As an illustrative example, we present the essence of the methodology by consid-
ering the example of the third order butter worth low pass LC ladder filter and its
current mode implementation. The prototype is shown in Fig. 9.36 from where it can
be seen that this circuit can be considered to be a cascade of three sub-sections.
Replacing each subsection by its corresponding MCCCII based realization and
then connecting them appropriately leads to the MCCCIIs based implementation
which is shown in Fig. 9.37 .
Using this technique it has been shown that filter design with cut off frequency of
5 MHz has been found to be easily tunable (by changing the bias current of
MCCCIIs) from 2.5 to 10 MHz with frequency accuracy within about 6 % and
with characteristic quite close to that of the passive prototype except beyond
100 MHz where the frequency response begins to deviate due to the frequency
limitations of the MCCCIIs.
Jiraseree-amornkun and Surakampontorn [ 32 ] have also successfully applied
this approach to realize current mode third order elliptic low pass ladder filter
employing five MCCCIIs with four grounded capacitors and have shown that
because this technique derives each elements with one by one replacement circuit,
it is possible to reduce the total number of MCCCIIs from five to three at the cost of
employing one floating capacitor in the design.
In general this method is not only quite simple but covers all types of passive LC
ladder prototypes. For designing an nth-order all-pole filter only nMCCCIIs are needed
whereas (2n-1) and (2n-2) MCCCIIs are required to design odd and even nth-order
elliptic filters respectively, when implementing only grounded capacitors are required.
9.12 Current-Controlled Sinusoidal Oscillators
There have been a number of proposals for realizing CC based sinusoidal oscilla-
tors, however, it is known that to realize such an oscillator, employing both
grounded capacitors, at least two CCs along with two capacitors and three resistors
are needed. Exploiting the current-controllable R x of the CCCIIs, it is interesting to
note that an electronically controllable sinusoidal oscillator can be realized with
only two CCCIIs along with both grounded capacitors as desirable for integrated
circuit implementation. The first such circuit was proposed by Horng [ 37 ] and is