OPA180-Q1 Datasheet, PDF (22/32 Pages) Texas Instruments – 0.1-uV/C Drift, Low-Noise, Rail-to-Rail Output, 36-V, Zero-Drift Operational Amplifiers

OPA180-Q1, OPA2180-Q1
SBOS861 – MAY 2017
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9.2.2 Discrete INA + Attenuation
The OPAx180-Q1 family can be used as a high-voltage, high-impedance front-end for a precision, discrete
instrumentation amplifier with attenuation. The INA159 shown in Figure 33 provides the attenuation that allows
this circuit to simply interface with 3.3-V or 5-V analog-to-digital converters (ADCs).
15 V
V_DIFF / 2
+
VCM
10
-V_DIFF / 2
U2
½
OPA2180-Q1
-15 V
R₅
1 kW
R_G
500 W
R₇
1 kW
-15 V
U5
½
OPA2180-Q1
V_OUTP
3.3 V
Ref 1
U1
INA159
Ref 2
Sense
V_OUTN
V_OUT
15 V
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Figure 33. Discrete INA + Attenuation for ADC With a 3.3-V Supply
9.2.3 RTD Amplifier
The OPAx180-Q1 is excellent for use in analog linearization of resistance temperature detectors (RTDs). The
following circuit, Figure 34, combines the precision of the OPAx180-Q1 amplifier and the precision reference of
theREF5050 to linearize a Pt100 RTD.
15 V
1 mF
(5 V)
R₂
49.1 kW
Out
In
REF5050
R₃
60.4 kW
1 mF
R₁
4.99 kW
OPA2180-Q1
V_OUT
0°C = 0 V
200°C = 5 V
RTD
Pt100
R₅
105.8 kW⁽¹⁾
R₄
1 kW
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(1) R₅ provides positive-varying excitation to linearize output.
Figure 34. RTD Amplifier With Linearization
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