OPA4277-EP Datasheet, PDF (11/20 Pages) Texas Instruments – OPA4277-EP High Precision Operational Amplifier

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8 Application and Implementation
OPA4277-EP
SBOS714 – NOVEMBER 2014
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
The OPA4277 is unity-gain stable and free from unexpected output phase reversal, making it easy to use in a
wide range of applications. Applications with noisy or high-impedance power supplies may require decoupling
capacitors close to the device pins. In most cases, 0.1-μF capacitors are adequate.
8.2 Typical Application
V+
0.1µF
Trim Range: Exceeds
Offset Voltage Specification
20kΩ
7
21
8
3 ^{OPA4277 6}
0.1µF ⁴
OPA4277 single op amp only.
Use offset adjust pins only to null
offset voltage of op amp—see text.
V–
Figure 22. OPA4277 Offset Voltage Trim Circuit
8.2.1 Design Requirements
For the thermocouple low-offset, low-drift loop measurement with diode cold junction compensation (see
Figure 25), Table 1 lists the design parameters needed with gain = 50.
G 1  ^2RF 50
R
(1)
Table 1. Design Parameters
DESIGN PARAMETER
R_F
R
EXAMPLE VALUE
10 kΩ
412 Ω
8.2.2 Detailed Design Procedure
8.2.2.1 Offset Voltage Adjustment
The OPA27 is laser-trimmed for very-low offset voltage and drift so most circuits do not require external
adjustment. However, offset voltage trim connections are provided on pins 1 and 8. The user can adjust offset
voltage by connecting a potentiometer as shown in Figure 22. Only use this adjustment to null the offset of the
operational amplifier. This adjustment should not be used to compensate for offsets created elsewhere in a
system because this can introduce additional temperature drift.
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