First, Second and Higher Order Filter Design Using Current Conveyors - Current Conveyors: Variants, Applications and Hardware Implementations - page 177

a b

(− +

V 1

y CCII

V 1

Y 1

V n−1

+ z+

x −

Y 1

Y n

(− +

V n y CCII

+ z−

x −

V n

Y n Y n−1

Fig. 6.48 (a) CCII-based sub-network (b) its associated graph (Adapted from [ 40 ] © 1992 Wiley)

CCII-based sub-network and (b) shows its sub flow graph. If the nth-order transfer
function is represented by a suitable signal flow graph composed of sub-graphs of
the form of Fig. 6.48b , then the corresponding circuit realization can be found easily
as demonstrated in [ 40 ].

If we consider the general form of the nth-order voltage transfer function given
by:

a 0 s 0 a 1 s 1 a 2 s 2 a n 1 s n 1 a n s n

V 0
V i ¼

þ þ þ ... þ þ

ð 6 : 67 Þ

b 0 þ b 1 s 1 þ b 2 s 2 þ ... þ b n 1 s n 1 þ b n s n

the signal flow graph representation of the above transfer function and its final
CC-based implementation as per the procedure outlined in [ 40 ] turns out to be as
shown in Fig. 6.49a, b respectively.
It is worth noting that to realize a general nth-order transfer function this method
requires at most n + 1 grounded capacitors (out of which n capacitors can be equal),
3n-1 resistors (out of which n-1 can be equal) and 3n-2 CCs. Furthermore, this
method can also be applied to the synthesis of the transfer functions having negative
coefficients.

Concluding Remarks
From the references [ 1 - 166 ] given at the end of this chapter, it is apparent that
a vast amount of literature exists on the realization of analog continuous time
filters using CCs. From this repertoire of CC-based filter circuits, in this
chapter, we have presented a selected number of configurations and have
highlighted their salient features. Thus, we presented some representative

(continued)