Basic Analog Circuit Building Blocks Using CCs and Application of CCs in Impedance Synthesis - Current Conveyors: Variants, Applications and Hardware Implementations - page 90

a b

I 1

I 1

CCII± CCII±

z

I 0

I 2
I 3

x
y

I 2
I 3

x
y

z

I n

I n i 1

CCII±
z

I 0

x
y

i 2
i 3

i n

Fig. 5.10 Current-mode summers (a) single-CC adder (b) adder/subtractor

Lastly, for the circuit of Fig. 5.11c , the output voltage is given by

V 1
R 1 þ

V 2
R 2 þ

V 3
R 3 þ :::: þ

V n
R n

V 0 ¼ R 0 ð 5 : 21 Þ

The circuit of Fig. 5.1c has the attractive feature of offering ideally infinite input
impedance at all its input terminals, providing voltage output from a low impedance
terminal and employing all grounded resistors.

5.2.6 Grounded Negative Impedance Converters

The negative impedance converter (NIC) is the basic 2-port active element which
may be used to create negative circuit impedances. Although the use of negative
impedances as employed in filters is handicapped by their associated notorious
stability problems, there are several applications such as in oscillators, loss-
compensation or frequency range extension where negative impedances can still
be put to use effectively by judicious design.
In view of the above, a study of techniques and circuits to create negative
elements using CCs is interesting and important. An NIC can be implemented by
a CCI by using only its x and y ports; whereas it is realizable from a CCII+ by
shorting its y and z terminals thereby leading to four different circuits to create a
grounded negative impedance equal to

Z L (see Fig. 5.12 ).