Hardware Reference
In-Depth Information
a
b
I
f
f
X
−
I
x+
x+
f
X
g
m
CCII+
CFTA±
Z
+
x−
Y
X
I
x-
Z
I
z
z
V
z
Fig. 11.14 CFTA realization (a) block diagram implementation (b) Implementation of the CFTA
using CCII and OTA [
87
]
a
b
I
A
I
B1
I
B2
+I
x
I
p
I
B1
I
B2
V
x+
I
A
x+
p
V
p
z
p
MO-CCCTTA
n
I
n
−I
x
MO-CCCTTA
I
in2
I
in1
V
n
x
−x
z
x−
V
x−
I
out
n
I
z
V
z
Fig. 11.15 The CTTA and its application (a) Block diagram (b) Current-mode multiplier/divider
[
107
]
V
T
2
I
A
;
I
B
1
2
V
T
,
g
m
2
¼
I
B
2
2
V
T
where
R
i
¼
g
m
1
¼
ð
11
11
Þ
:
An interesting application of this block was proposed by Pisutthipong and
Siripruchyanun [
107
] in realizing a current mode multiplier/divider as shown in
Fig.
11.15b
. A novel feature is this circuit is that does not require even a single
external passive component and both the function are realized in the same circuit.
By a straight forward analysis of this circuit, taking cognizance of its character-
izing equations, the current output of the circuit in terms of the two input currents is
found to be
I
in
1
I
in
2
8
I
A
I
out
¼
ð
11
12
Þ
:
:
From the above equation, it is clear the circuit functions as a four-quadrant multiplier
because both the input currents can be either positive or negative. A novel feature of
this circuit is that its performance is
temperature-insensitive
. Furthermore, if either
I
in1
or I
in2
and I
A
are the input currents, the proposed circuit can also function as a
current-mode divider although in this case, since I
a
cannot have negative value, the
realized analog divider would be only a two-quadrant divider.
Search WWH ::
Custom Search