Datasheet

R
1
R
2
R
3
R
4
10 k:
V
IN
V
OUT
+
-
V
+
V
-
+
-
V
+
V
-
= 1 +
R
2
R
1
R
4
R
3
+
V
OUT
+
-
-
R
A
C
F
V
IN
= KI
+
-
IR RADIATION
INTENSITY, I
THERMOPILE
R
B
V
OUT
R
A
K(R
A +
R
B
)
I =
LMP7715, LMP7716, LMP7716Q
SNOSAV0E –MARCH 2006–REVISED MARCH 2013 www.ti.com
Figure 56. Thermopile Sensor Interface
PRECISION RECTIFIER
Rectifiers are electrical circuits used for converting AC signals to DC signals. Figure 57 shows a full-wave
precision rectifier. Each operational amplifier used in this circuit has a diode on its output. This means for the
diodes to conduct, the output of the amplifier needs to be positive with respect to ground. If V
IN
is in its positive
half cycle then only the output of the bottom amplifier will be positive. As a result, the diode on the output of the
bottom amplifier will conduct and the signal will show at the output of the circuit. If V
IN
is in its negative half cycle
then the output of the top amplifier will be positive, resulting in the diode on the output of the top amplifier
conducting and delivering the signal from the amplifier's output to the circuit's output.
For R
2
/ R
1
≥ 2, the resistor values can be found by using the equation shown in Figure 57. If R
2
/ R
1
= 1, then R
3
should be left open, no resistor needed, and R
4
should simply be shorted.
Figure 57. Precision Rectifier
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