Hardware Reference
In-Depth Information
V
B
I
B
-
+
I
3
I
1
D
1
D
3
D
7
D
5
CCII+
Y
X
CCII+
I
Z
IZ
Y
X
A
Z
Z
B
D
4
D
2
I
2
D
8
I
4
D
6
V
in
R
I
0
R
f
+
I
C
V
0
Fig. 8.6 Precision full-wave rectifier proposed by Wilson and Mannama [
6
]
A routine analysis of the circuit using translinear (TL) principle applied to the
TL loop consisting of the four diodes D1-D4, the following equation results for the
output voltage of the circuit:
n
o
1
=
2
2
I
B
V
o
¼
R
f
ð
V
in
=
R
Þ
þ
ð
8
:
3
Þ
The effect of bridge bias current has been found to be negligible for low bias currents.
The workability of this circuit has been tested [
6
] using CCII+ from AD844,
transimpedance amplifier realized with AD847 and a bridge bias current of 40
μ
A
with ICs biased with
15 V, voltage swings greater than 10 V were attainable.
Monpapassorn [
21
] has recently introduced another two-CC full wave rectifier
which is shown here in Fig.
8.7
. Assuming that the DC bias currents I
1
,I
2
and I
3
are
zero, the operation of the circuit can be explained as follows:
When V
in
is positive diode D
1
is ON and current +V
in
/R
1
flows out of the
Z-terminal of CCII+ 1. On the other hand, when V
in
is negative, D
2
conducts and
a current
V
in
/R
2
, even the current coming out of the terminal-Z is still positive and
equal to +V
in
/R
1
. As a consequence, full wave rectified output is available with V
0
given by
V
in
;
R
L
R
in
þ
V
out
¼
þ
for V
in
>
0 as well as for V
in
<
0
ð
8
:
4
Þ
R
x
where R
1
¼R
2
¼R
in
If one chooses R
L
¼ (R
1
+R
x
) ¼ (R
2
+R
x
) then the magnitudes of the input and
output waveforms would be equal. Also, the output impedance is given by R
z
//R
L
which is smaller than other earlier full wave rectifiers, for smaller values of R
L.
The workability of this circuit has been demonstrated [
21
] by realizing the circuit
withAD844 CCII+, R
1
¼
R
2
¼
50
ʩ
R
L
¼
100
ʩ
so that withR
x
¼
50
ʩ
for theAD844
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