OPA171-Q1_15 Datasheet, PDF (15/36 Pages) Texas Instruments – OPAx171-Q1 36-V, Single-Supply, General-Purpose Operational Amplifier

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Feature Description (continued)
Output
OPA171-Q1, OPA2171-Q1, OPA4171-Q1
SBOS556B – JUNE 2011 – REVISED DECEMBER 2014
+18V
OPA171
-18V
37VPP
Sine Wave
(±18.5V)
Output
Time (100ms/div)
Figure 37. No Phase Reversal
7.3.3 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.
50
R_L = 10kW
45
40
35
30
25
20
G = +1
15
R_OUT = 0W
+18V
ROUT
10
R_OUT = 25W
OPA171
-18V
RL
CL
5
R_OUT = 50W
0
0 100 200 300 400 500 600 700 800 900 1000
Capacitive Load (pF)
Figure 38. Small-Signal Overshoot versus Capacitive Load
(100-mV Output Step)
50
45
R_OUT = 0W
40
R_OUT = 25W
35
R_OUT = 50W
30
25
20
15
10
5
0
0
RI = 10kW
RF = 10kW
+18V
OPA171
-18V
G = -1
ROUT
CL
100 200 300 400 500 600 700 800 900 1000
Capacitive Load (pF)
Figure 39. Small-Signal Overshoot versus Capacitive Load
(100-mV Output Step)
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Product Folder Links: OPA171-Q1 OPA2171-Q1 OPA4171-Q1