lm6142qml National Semiconductor Corporation, lm6142qml Datasheet - Page 12

• Manufacturer Part Number: lm6142qml
• Description: 17 Mhz Rail-to-rail Input-output Operational Amplifiers
• Manufacturer: National Semiconductor Corporation

www.national.com
LM6142 Application Ideas
These features allow the LM6142 to drive capacitive loads
as large as 1000pF at unity gain and not oscillate. The scope
photos (Figure 3 and Figure 4) above show the LM6142
driving a l000pF load. In Figure 3, the upper trace is with no
capacitive load and the lower trace is with a 1000pF load.
Here we are operating on
pulse. Excellent response is obtained with a C
Figure 4, the supplies have been reduced to
pulse is 4 V
compensation capacitor is best established after the board
layout is finished because the value is dependent on board
stray capacity, the value of the feedback resistor, the closed
loop gain and, to some extent, the supply voltage.
Another effect that is common to all op amps is the phase
shift caused by the feedback resistor and the input capaci-
tance. This phase shift also reduces phase margin. This
effect is taken care of at the same time as the effect of the
capacitive load when the capacitor is placed across the
feedback resistor.
The circuit shown in Figure 5 was used for these scope
photos.
PP
and C
f
is 39pF. The best value for the
±
12V supplies with a 20 V
(Continued)
f
±
of l0pF. In
2.5V, the
PP
FIGURE 2.
12
FIGURE 3.
FIGURE 4.
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20144008
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