OPA180_15 Datasheet, PDF (20/38 Pages) Texas Instruments – Drift, Low-Noise, Rail-to-Rail Output, 36-V, Zero-Drift Operational Amplifiers

OPA180, OPA2180, OPA4180
SBOS584D – NOVEMBER 2011 – REVISED MAY 2014
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9.2.2 Discrete INA + Attenuation
The OPA180 can be used as a high-voltage, high-impedance front-end for a precision, discrete instrumentation
amplifier with attenuation. The INA159 provides the attenuation that allows this circuit to easily 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
-15 V
R₅
1 kW
R_G
500 W
R₇
1 kW
-15 V
U5
½
OPA2180
V_OUTP
3.3 V
Ref 1
U1
INA159
Ref 2
Sense
V_OUTN
V_OUT
15 V
Figure 33. Discrete INA + Attenuation for ADC with 3.3-V Supply
9.2.3 RTD Amplifier
The OPA180 is excellent for use in analog linearization of resistance temperature detectors (RTDs). The below
circuit combines the precision of the OPA180 amplifier and the precision reference REF5050 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
RTD
Pt100
OPA2180
R₅
105.8 kW⁽¹⁾
V_OUT
0°C = 0 V
200°C = 5 V
R₄
1 kW
(1) R₅ provides positive-varying excitation to linearize output.
Figure 34. RTD Amplifier with Linearization
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