Datasheet

40
35
30
25
20
15
10
5
0
Overshoot (%)
0 100 200 300 400 500 600 700 800 900 1000
Capacitive Load (pF)
+18 V
-18 V
R
OUT
C
L
Device
R
L
G = +1
R = 0 W
OUT
R = 25 W
OUT
R = 50 W
OUT
R = kW
L
10
40
35
30
25
20
15
10
5
0
Overshoot (%)
0 100 200 300 400 500 600 700 800 900 1000
Capacitive Load (pF)
Device
R =
I
10 kW
R
OUT
C
L
R
F
= 10 kW
+18 V
-18 V
G = 1-
R = 0 W
OUT
R = 25 W
OUT
R = 50 W
OUT
R = 10 kW
L
Time(100 s/div)m
5V/div
+18V
-18V
37V
PP
SineWave
( 18.5V)±
Device
V
IN
V
OUT
OPA4188
SBOS641B –JUNE 2012–REVISED MARCH 2013 www.ti.com
GENERAL LAYOUT GUIDELINES
For best operational device performance, good printed circuit board (PCB) layout practices are recommended.
Low-loss, 0.1-µF bypass capacitors should be connected between each supply pin and ground, placed as close
to the device as possible. A single bypass capacitor from V+ to ground is applicable to single-supply applications.
PHASE-REVERSAL PROTECTION
The OPA4188 has an internal phase-reversal protection. Many op amps 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 OPA4188 input prevents phase reversal with excessive common-mode voltage. Instead,
the output limits into the appropriate rail. This performance is shown in Figure 40.
Figure 40. No Phase Reversal
CAPACITIVE LOAD AND STABILITY
The OPA4188 dynamic characteristics have been optimized for a range of common operating conditions. The
combination of low closed-loop gain and high capacitive loads decreases the amplifier phase margin 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 41 and Figure 42 illustrate graphs of small-signal overshoot versus capacitive load for several
values of R
OUT
. Also, refer to the Applications Report, Feedback Plots Define Op Amp AC Performance
(SBOA015), available for download from www.ti.com, for details of analysis techniques and application circuits.
Figure 41. Small-Signal Overshoot versus Figure 42. Small-Signal Overshoot versus
Capacitive Load (100-mV Output Step) Capacitive Load (100-mV Output Step)
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