Hardware Reference
In-Depth Information
7
+Vcc
Q
17
Q
18
Q
15
Q
7
Q
8
Q
5
D
3
D
1
Q
2
Q
13
V
in
Q
11
Q
1
X
Z
Q
12
Q
4
V
0
Y
2
8
6
5
3
Q
3
D
4
Q
14
D
2
Q
6
Q
9
Q
16
Q
10
Q
19
Q
20
50k
100
−Vcc
IQ Adj
1
RQ(ext.)
4
Fig. 3.24 Internal circuit architecture of OPA660 OTA which is essentially a CCII+ and a VF
[
23
,
24
]
slew rate. It is popularly referred to in the literature as a d
iamond transistor
since
the CCII part acts like almost an ideal transistor and it is for this reason that the
terminals X, Y and Z are respectively labeled as E (emitter), B (Base) and C
(Collector). Of late, OPA860 has been extensively used in the literature as current
conveyor to realize a variety of building blocks.
Concluding Remarks
This chapter was concerned with the bipolar implementation of current
conveyors and has dealt with two types of bipolar CCs (i) a variety of bipolar
CC architectures proposed in literature for implementing CCII as well as CCI
having some specific features of interest such as electronic control of current
gain, enhanced input impedance at terminal Y, reduced input impedance at
terminals X etc. (ii) bipolar CCs which are available as of the shelf ICs such
as PA630, LTPCC201, AD844, OPA2662, OPA660/860.
It is a matter of great curiosity to note that except the first two of this list all
the remaining ones in spite of containing a CCII+ architecture internally and
also having external access to the three terminals of the inherent CCII have
neither been claimed as CCs in the nomenclature nor have been explicitly
identified in the data sheet as a CC! Nevertheless, all of these have been used
quite frequently in the literature by researchers and academicians as current
conveyors. It is believed that after a clear cut identification of the above
mentioned ICs as CCs, the readers and circuit designers would take advantage
of this exposition and would be able to practically implement their CCI/CCII
based functional circuits using any of the available variants discussed in this
chapter.
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