OPA171_15 Datasheet, PDF (17/43 Pages) Texas Instruments – Single-Supply, SOT553, General-Purpose Operational Amplifiers

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OPA171, OPA2171, OPA4171
SBOS516E – SEPTEMBER 2010 – REVISED JUNE 2015
Feature Description (continued)
7.3.3 Phase-Reversal Protection
The OPAx171 family has an internal phase-reversal protection. Many operational amplifiers exhibit a phase
reversal when the input is driven beyond its linear common-mode range. This condition is most often
encountered in noninverting circuits when the input is driven beyond the specified common-mode voltage range,
causing the output to reverse into the opposite rail. The input of the OPAx171 prevents phase reversal with
excessive common-mode voltage. Instead, the output limits into the appropriate rail. This performance is shown
in Figure 37.
Output
+18V
OPA171
-18V
37VPP
Sine Wave
(±18.5V)
Output
Time (100ms/div)
Figure 37. No Phase Reversal
Table 2. Typical Performance Range
PARAMETER
Input Common-Mode Voltage
Offset voltage
vs Temperature
Common-mode rejection
Open-loop gain
GBW
Slew rate
Noise at f = 1kHz
MIN
(V+) – 2
TYP
MAX UNIT
(V+) + 0.1
V
7
mV
12
µV/°C
65
dB
60
dB
0.7
MHz
0.7
V/µs
30
nV/√Hz
7.3.4 Capacitive Load and Stability
The dynamic characteristics of the OPAx171-Q1 family of devices have been optimized for commonly
encountered operating conditions. The combination of low closed-loop gain and high capacitive loads decreases
the phase margin of the amplifier and can lead to gain peaking or oscillations. As a result, heavier capacitive
loads must be isolated from the output. The simplest way to achieve this isolation is to add a small resistor (for
example, R_OUT equal to 50 Ω) in series with the output. Figure 38 and Figure 39 show small-signal overshoot
versus capacitive load for several values of R_OUT. Also, for details of analysis techniques and application circuits,
refer to the Applications Bulletin AB-028 (SBOA015), available for download from TI.com.
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