Second Generation Controlled Current Conveyors (CCCII) and Their Applications - Current Conveyors: Variants, Applications and Hardware Implementations - page 258

Fig. 9.14 Sum and
difference amplifiers
proposed by
Maheshwari [ 12 ]

I B2

I B1

V 2

Y

V 1

Y

2

1

Z±

Z+

X

X

X

Y

3 I B3

Z+

V 0

V 1
R x 1

V 2
R x 2

V o ¼ R x 3 ð 9 : 10 Þ

From the above equation it is clear that with the choice for CCCII as positive ,a
summing amplifier is realized and with the choice for CCCII as negative ,a
difference amplifier is realized.

9.6 Instrumentation Amplifiers

A traditional instrumentation amplifier typically requires as many as three op-amps
along with seven resistors out of which, at least four are required to be identical.
This circuit although provides a single-resistance-controllable variable gain with
infinite input impedance at both the input terminals and zero output impedance at
the output terminal, but suffers from the conflict between the maximum gain and
the available bandwidth. This gain-bandwidth-conflict can be avoided by using
either a three-CCII-based circuit or a three current feedback op-amp (CFOA) based
circuit. Both these circuits use bare minimum of (only two) resistors for varying the
voltage gain. Using CCCIIs however, an instrumentation amplifier can be made
with only three active building blocks without requiring any external resistors .In
addition, the voltage gain can be controlled through the external DC bias currents.
One such circuit proposed by Maheshwari [ 13 ] is shown in Fig. 9.15 which is
characterized by:

2 R x 3
R x 1 þ

2 I B 1 I B 2
I B 3 I B 1 þ

V 0 ¼ ð V 1 V 2 Þ ¼ ð V 1 V 2 Þ ð 9 : 11 Þ

ð R x 2 Þ ð I B 2 Þ