Hardware Implementations of CCs Using Off-the-Shelf ICs - Current Conveyors: Variants, Applications and Hardware Implementations - page 23

, the non-inverting terminal of the OTA is left open; the base
of Q 1 is treated as Q y . In this case, Q 2 is off therefore, CM 2 is off while the collector
current Q 1 is (I B-ix ) which is carried over by CM 1 to CM 3 and then to the Z- terminal
of the circuit however, in this case, because the constant current source is connected
from positive supply rail to the terminal- Z therefore, i z can be seen to be

For realizing CCII

¼

(I B-ix )

and thus, the circuit realizes a CCII .

Since CA3280 has reportedly a gain bandwidth product of around 10 MHz, it is
expected that CCII+ and CCII

made by the above mentioned technique may be
expected to function at relatively high frequencies (of the order of several MHz).

2.2.6 Papazoglou-Karybakas ' Modified Version of Senani ' s
CC Implementation

Papazoglou and Karybakas [ 15 ], while presenting a non-interacting electronically
tunable CCII based current mode biquadratic filter, employed a slightly modified
version of Senani

s CC (see Fig. 1 therein) which is shown here in Fig. 2.9 . Note
that the DC bias current of the OTA which controls the transconductance gain g m of
the OTA is derived from an additional circuit consisting of an op-amp, two resistors
and PNP transistor thereby arranging that I B is equal to V c /R 1 . As a consequence the
current gain between i z and i x which is symbolically denoted as h 32 becomes
electronically controllable by external control voltage V c . Using this version of
the CCII, they succeeded in implementing biquadratic filter circuit whose cut off
frequency could be varied over a range of one decade through the external control
voltage V c .

'

2.2.7 Karybakas-Siskos-Laopoulos s Compensated,

'

Tunable CC

Karybakas et al. in [ 12 ] presented a novel CC configuration based upon an op-amp
and two OTAs which provides current gain tunability, has full compensation over
temperature variation and does not suffer from the disadvantages of gain temper-
ature dependence, input current non-linearities and CMRR effects. This circuit is
shown in Fig. 2.10 . By a routine analysis, it is easy to confirm that V x ¼

V y ,I y ¼ 0

I B 2 = 2 V T

ki x . Since i z

G 2 I B 2

and I z ¼

i x ¼ G 1 ¼ I B 1 = 2 V T ¼ I B 1 ¼

k , it is seen that the current gain is

independent of temperature.
From the same circuit, a CCII can also be realized by interchanging the input

terminals of the OTA connected at Z- port. It has been shown in [ 12 ] that by
changing I B2 , the current gain varied linearly over a range of three decades; the gain
value remains temperature independent over a temperature from 0 to 100 and