Integratable Bipolar CC Architectures and Commercially Available IC CCs - Current Conveyors: Variants, Applications and Hardware Implementations - page 38

+V

Current
mirror

Differential
Current
Ampliffier

I 1

I 2 +Ai x

2

Z

I 2 +i x

i z

Q 3

I 2

X

Q 1 Q 2

Y

Z L

I 2

I 1

−V

Fig. 3.7 The basic schematic of the electronically-controllable CC proposed by Surakampontorn
and Thitimajshima [ 8 ]

3.2.6 Filanovsky s Current Conveyor Modified

from a Current Source

'

The CCII structure proposed by Filanovsky [ 9 ] is actually obtained by appropriate
modification of a current source and can be explained by the circuit shown in
Fig. 3.8 . The transistor circuit consisting of Q 7, Q 8 ,Q 9 ,Q 10 ensures that two DC
bias currents, each equal to I B , are injected at nodes a and b in the circuit. If the of

transistors is very high then from the various total currents marked on the circuit of
Fig. 3.8 , it follows that the small signals at Y, X and Z ports are described by the
equations; i y ¼

β

0, v x ¼ v y and i z ¼ i x and the circuit, thus, realizes a CCII+.

3.2.7 Temperature-Compensated CCII

As in an OTA, the transconductance g m is given by g m ¼ I 0 /2V T , likewise in a

current conveyor the input resistance looking into port X is given by R x ¼ V T /2I 0 .

Since V T is directly proportion to absolute temperature, a method of temperature
compensation applicable to both translinear CC and OTA was presented by
Surakampontorn et al. [ 10 ]. The key idea of their preposition is the bias circuit
for temperature compensation as shown in Fig. 3.9 .