Other Building Blocks Having MTC or CC at Front-end and Their Applications - Current Conveyors: Variants, Applications and Hardware Implementations - page 346

Fig. 11.4 Implementation
of the OTRA using two
CCIIs and a voltage
buffer [ 23 ]

i 1

CCII+

V 1

X 1

Z 1

Y 1

CCII+

V 2

X 2

i 2

Z 2

1 V 0

Y 2

Voltage buffer

11.5 Current-Differencing-Buffered-Amplifier (CDBA)
and Its Variants

The CDBA was introduced as a new building block by Acar and Ozoguz in [ 27 ] and
is characterized by the equations V p ¼

V z . From the terminal
equation of the CDBA, it is clear that its CCII-based implementation can be nearly
same as that of the OTRA except that in the case of OTRA, the current output
terminal is left open to facilitate R m !

V n ¼ 0, i z ¼ i p i n ,V w ¼

0 whereas in case of the CDBA, this current
output terminal is to be loaded into an impedance Z L so that a voltage V Z is created
across it whose buffered version is then made available at the W terminal of
the CDBA.
If a current-controlled CDBA (CC-CDBA) is needed, the same can be realized
by the current sensing front-ends to be composed of the same mixed translinear
cells as employed in CCCII. This applies to both bipolar and CMOS
implementations of the CC-CDBAs. Consequently, a CC-CDBA can be
implemented from CCCIIs as shown in Fig. 11.5 .
An exemplary CDBA circuit exhibiting current-controllable input resistances at
its both p and n input terminals is shown here in Fig. 11.6 . A CC-CDBA is
characterized by V p ¼ R p I p ,V n ¼ R n I n ,I z ¼ I p -I n , and V w ¼ V z .

An interesting application of the CC-CDBA is in the realization of a very
compact current-mode analog multiplier/divider which is shown in Fig. 11.7 .
A routine analysis of the circuit reveals that the output current is given by

I A I C
2 I B

I 0 ¼ ð 11 6 Þ

:

From the above, it is seen that one can engage the circuit either as a multiplier by
taking I A and I C as the inputs or as a divider by taking I A and I B as inputs. However,
it should be noted that in both the cases, only two-quadrant operation is possible.
Two other novel applications of CC-CDBA are in the realization of floating
negative grounded and floating inductors. Two exemplary circuits to accomplish
this are shown in Fig. 11.8 and have the novelty of employing only two active
building blocks and a single grounded capacitor while providing electronically-
controlled inductance value.