Hardware Reference
In-Depth Information
C
1
R
2
αʲ
T
i
1
¼
ð
15
:
9
Þ
C
1
R
2
ʲʳ
T
i
2
¼
ð
15
:
10
Þ
T
d
1
¼
αʲ
C
2
R
1
ð
15
:
11
Þ
T
d
2
¼
ʲʳ
C
2
R
1
ð
15
:
12
Þ
In this case also, it may be noted that the parameters T
d
and T
i
can be controlled
through R
1
and R
2
respectively whereas the constant K
p
can be adjusted by the
multiplier constant, a, which can be controlled if the DOCCII is realized as an
electronically-controllable current conveyor. Finally, if a CMOS DOCCII is
employed, the resistors R
1
and R
2
could be both CMOS voltage-controlled-resistors
thereby permitting the change of their values through external control voltages.
When both the admittances are chosen as resistors, then the same circuit realizes
a current mode instrumentation amplifier with the two outputs being given by:
ʲ
R
1
R
2
I
01
¼
α
I
1
I
2
ð
15
:
13
Þ
I
02
¼
ʲ
R
1
R
2
I
1
I
2
ʳ
ð
:
Þ
15
14
The expression for CMRR is given by:
¼
ʲ
ð
R
1
=
2
R
2
Þ þ
ðÞ
=
1
2
CMRR
ð
15
:
15
Þ
ð
ʲ
R
1
=
R
2
Þ
1
From equation (
15.15
), it is seen that for the case of unity gain i.e. R
1
¼
R
2
, CMRR
approaches infinity.
It has been demonstrated by Yuce and Minaei [
2
] that using a CMOS DOCCII
implemented in 0.13
ʼ
m TSMC CMOS technology with DC power supply
voltages
¼
1 V, the circuit has performed as stipulated by theoretical analysis.
15.3 Wide-Band Controllable Low Noise Amplifiers
A new application of current conveyors namely, the design of wide band control-
lable low noise amplifiers (LNAs), was proposed by Godara and Fabre in [
3
]. The
proposed structure is shown symbolically in Fig.
15.3a
whereas
15.3b
shows a
transistor level implementation of the same basic idea. The new LNAs have been
shown to provide the following important advantages (i) complete elimination of
the requirement of any passive components (ii) wide band performance, with stable
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