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| OPA172IDR Datasheet, PDF (19/29 Pages) Texas Instruments – 36-V Single-Supply 10-MHz Rail-to-Rail Output Operational Amplifiers | |||
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OPA172
OPA2172
OPA4172
SBOS618 â DECEMBER 2013
APPLICATION EXAMPLES
The following application examples highlight only a few of the circuits where the OPAx172 can be used.
BI-DIRECTIONAL CURRENT SOURCE
The improved Howland current pump topology shown in Figure 46 provides excellent performance due to the
extremely tight tolerances of the on chip resistors of the INA132. By buffering the output using and OPA172, the
output current the circuit is able to deliver is greatly extended.
The circuit dc transfer function is show in Equation 1:
IOUT = VIN / R1
(1)
The OPA172 can also be used as the feedback amplifier because the low bias current will minimize error
voltages produced across R1. However, for improved performance, a FET-input device with extremely low offset
can be selected, such as the OPA192, OPA140, or OPA188 for the feedback amplifier.
IN-
40k
40k
SENSE
VIN
-
OUTPUT
OPA172
++
+
-
40k
40k
REF
IN+
INA132
R1
OPA172
++
-
I OUT
Figure 46. Bidirectional Current Source
Copyright © 2013, Texas Instruments Incorporated
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Product Folder Links: OPA172 OPA2172 OPA4172
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