Hardware Reference
In-Depth Information
C
M
repeate
r
C
M
C
M
Bas
e co
m
pensated
CM
+V
CC
+V
CC
Z
Y
−V
SS
+V
CC
X
W
−V
SS
−V
SS
CM repeater
CM
CM
Base compensated CM
Fig. 10.4
Equivalent circuit of an exemplary CMOS implementation of the OFC proposed by
Toumazou et al. [
5
]
The OFC is particularly useful in the realization of controlled sources with a
minimum possible number of external passive elements. For this purpose, it is used
in closed loop with current feedback from node w to x achieving a current feedback
resulting in the gain-bandwidth decoupling while the translinear cell between ports
y and x ensures a high slew rate due to the Sinh characteristics between the
differential input (v
y
-v
x
) and the current i
x
. Thus, the various controlled sources
can be realized with the OFC using a bare minimum number of passive compo-
nents, achieving the ideal input and output impedances and with each configuration
exhibiting the pleasing property of gain bandwidth independence. The various
realizations of the controlled sources using a single OFC, possessing these proper-
ties, are shown in Fig.
10.5
.
10.2.4 Third Generation Current Conveyor
The third generation current conveyor (CCIII) was introduced by Fabre in 1995 [
6
]
as a new helpful active element characterized by the hybrid matrix:
2
3
2
3
2
3
i
y
v
x
i
z
0
10
100
0
v
y
i
x
v
z
4
5
¼
4
5
4
5
ð
10
:
4
Þ
10
The CCIII was conceived to be useful element to be used as the input cell of probes
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