OP297S Просмотр технического описания (PDF) - Analog Devices
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OP297S Datasheet PDF : 16 Pages
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APPLICATION CIRCUITS
PRECISION ABSOLUTE VALUE AMPLIFIER
The circuit in Figure 31 is a precision absolute value amplifier
with an input impedance of 30 MΩ. The high gain and low
TCVOS of the OP297 ensure accurate operation with microvolt
input signals. In this circuit, the input always appears as a
common-mode signal to the op amps. The CMR of the OP297
exceeds 120 dB, yielding an error of less than 2 ppm.
+15V
C2
0.1µF
R1
R3
1kΩ
1kΩ
C1
30pF
2– 8
1/2 1
OP297
VIN
3+
C3
0.1µF
4
D1
1N4148
D2
1N4148
5–
1/2
OP297
6+
7
0V < VOUT < 10V
R2
2kΩ
–15V
Figure 31. Precision Absolute Value Amplifier
PRECISION CURRENT PUMP
Maximum output current of the precision current pump shown
in Figure 32 is ±10 mA. Voltage compliance is ±10 V with
±15 V supplies. Output impedance of the current transmitter
exceeds 3 MΩ with linearity better than 16 bits. R1 through R4
should be matched resistors.
R3
10kΩ
R1
10kΩ
2–
R5
VIN
R2
10kΩ
1/2 1 100kΩ
OP297
3+
+15V
IOUT
10mA MAX
R4
8
5
IOUT =
VIN
R5
=
VIN
100Ω
= 10mA/V
10kΩ 7 1/2
OP297
6
–15V
Figure 32. Precision Current Pump
OP297
PRECISION POSITIVE PEAK DETECTOR
In Figure 33, the CH must be of polystyrene, Teflon®, or
polyethylene to minimize dielectric absorption and leakage.
The droop rate is determined by the size of CH and the bias
current of the OP297.
1kΩ
+15V
1N4148
0.1µF
2–
1/2 1
VIN
1kΩ 3 OP297
+
RESET
1kΩ
6–
1/2 7
1kΩ
OP297
5+
CH
0.1µF
2N930
–15V
VOUT
Figure 33. Precision Positive Peak Detector
SIMPLE BRIDGE CONDITIONING AMPLIFIER
Figure 34 shows a simple bridge conditioning amplifier using
the OP297. The transfer function is
VOUT
= VREF ⎜⎝⎛
R
ΔR
+ ΔR
⎟⎠⎞
RF
R
The REF43 provides an accurate and stable reference voltage for
the bridge. To maintain the highest circuit accuracy, RF should
be 0.1% or better with a low temperature coefficient.
15V
REF43
4
VREF
R + ΔR
RF
2–
1/2 1
3
OP297
+
VOUT
6– 8
1/2 7
OP297
5+
4
VOUT = VREF
ΔR
R + ΔR
RF
R
Figure 34. Simple Bridge Condition Amplifier Using the OP297
Rev. G | Page 11 of 16
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