OPA2192 Datasheet, PDF (21/51 Pages) Texas Instruments – OPAx192 36-V, Precision, Rail-to-Rail Input/Output, Low Offset Voltage,Low Input Bias Current Op Amp with e-trim

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7 Parameter Measurement Information
OPA192, OPA2192, OPA4192
SBOS620D – DECEMBER 2013 – REVISED SEPTEMBER 2015
7.1 Input Offset Voltage Drift
The OPAx192 family of operational amplifiers is manufactured using TI’s e-trim technology. Each amplifier input
offset voltage and input offset voltage drift is trimmed in production, thereby minimizing errors associated with
input offset voltage and input offset voltage drift. The e-trim technology is a TI proprietary method of trimming
internal device parameters during either wafer probing or final testing. When trimming input offset voltage drift the
systematic or linear drift error on each device is trimmed to zero. This results in the remaining errors associated
with input offset drift are minimal and are the result from only nonlinear error sources. Figure 49 illustrates this
concept.
V_OS Before e-trim
V_OS After e-trim
Linear component of drift
Linear component of drift
Temperature
Figure 49. Input Offset Before and After Drift Trim
A common method of specifying input offset voltage drift is the box method. The box method estimates a
maximum input offset drift by bounding the offset voltage versus temperature curve with a box and using the
corners of this bounding box to determine the drift. The slope of the line connecting the diagonal corners of the
box corresponds to the input offset voltage drift. Figure 50 shows the box method concept. The box method
works particularly well when the input offset drift is dominated by the linear component of drift, but because the
OPA192 family uses TI’s e-trim technology to remove the linear component input offset voltage drift, the box
method is not a particularly useful method of accurately performing an error analysis. Figure 50 shows 30 typical
units of the OPAx192 with the box method superimposed for illustrative purposes. The boundaries of the box are
determined by the specified temperature range along the x-axis and the maximum specified input offset voltage
across that same temperature range along the y-axis. Using the box method predicts an input offset voltage drift
of 0.9 µV/°C. As shown in Figure 50, the slopes of the actual input offset voltage versus temperature are much
less than that predicted by the box method. The box method predicts a pessimistic value for the maximum input
offset voltage drift and is not recommended when performing an error analysis.
Offset Voltage vs Temperature
100
75
50
25
0
-25
-50
-75
-100
-50 -25 0
25 50 75 100 125 150
Temperature (GC)
Figure 50. The Box Method
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