OPA180_15 Datasheet, PDF (17/38 Pages) Texas Instruments – Drift, Low-Noise, Rail-to-Rail Output, 36-V, Zero-Drift Operational Amplifiers

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OPA180, OPA2180, OPA4180
SBOS584D – NOVEMBER 2011 – REVISED MAY 2014
9 Application and Implementation
9.1 Application Information
The OPAx180 family offers excellent dc precision and ac performance. These devices operate up to 36-V supply
rails and offer rail-to-rail output, ultra-low offset voltage, and offset voltage drift as well as 2-MHz bandwidth.
These features make the OPAx180 a robust, high-performance amplifier for high-voltage industrial applications.
9.2 Typical Applications
These application examples highlight only a few of the circuits where the OPAx180 can be used.
9.2.1 Bipolar ±10-V Analog Output from a Unipolar Voltage Output DAC
This design is used for conditioning a unipolar digital-to-analog converter (DAC) into an accurate bipolar signal
source using the OPA180 and three resistors. The circuit is designed with reactive load stability in mind and is
compensated to drive nearly any conventional capacitive load associated with long cable lengths.
R_G1
R_FB
V_REF
C_COMP
R_G2
V_OUT
DAC8560
+
Device
R_ISO
C_LOAD
Figure 30. Circuit Schematic
9.2.1.1 Design Requirements
The design requirements are as follows:
• DAC supply voltage: +5-V dc
• Amplifier supply voltage: ±15-V dc
• Input: 3-wire, 24-bit SPI
• Output: ±10-V dc
9.2.1.2 Detailed Design Procedure
9.2.1.2.1 Component Selection
DAC: For convenience, devices with an external reference option or devices with accessible internal references
are desirable in this application because the reference is used to create an offset. The DAC selection in this
design should primarily be based on dc error contributions typically described by offset error, gain error, and
integral nonlinearity error. Occasionally, additional specifications are provided that summarize end-point errors of
the DAC typically called zero-code and full-scale errors. For ac applications, additional consideration may be
placed on slew rate and settling time.
Amplifier: Amplifier input offset voltage (V_IO) is a key consideration for this design. V_IO of an operational amplifier
is a typical data sheet specification but in-circuit performance is also affected by drift over temperature, the
common-mode rejection ratio (CMRR), and power-supply rejection ratio (PSRR); thus consideration should be
given to these parameters as well. For ac operation, additional considerations should be made concerning slew
rate and settling time. Input bias current (I_IB) can also be a factor, but typically the resistor network is
implemented with sufficiently small resistor values that the effects of input bias current are negligible.
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Product Folder Links: OPA180 OPA2180 OPA4180