lmh6733mqx National Semiconductor Corporation, lmh6733mqx Datasheet - Page 12

• Manufacturer Part Number: lmh6733mqx
• Description: Single Supply, 1.0 Ghz, Triple Operational Amplifier
• Manufacturer: National Semiconductor Corporation

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ACTIVE FILTER
The choice of reactive components requires much attention
when using any current feedback operational amplifier as an
active filter. Reducing the feedback impedance, especially at
higher frequencies, will almost certainly cause stability prob-
lems. Likewise capacitance on the inverting input should be
avoided. See Application Notes OA-7 and OA-26 for more in-
formation on Active Filter applications for Current Feedback
Op Amps.
When using the LMH6733 as a low pass filter the value of
R
in the R
creased gain at higher frequencies, which improves attenua-
tion in the stop band. Stability problems are avoided because
in the stop band additional device bandwidth is used to cancel
the input signal rather than amplify it. The benefit of this
change depends on the particulars of the circuit design. With
a high pass filter configuration reducing R
device instability and is not recommended.
F
can be substantially reduced from the value recommended
F
vs. Gain charts. The benefit of reducing R
FIGURE 4. Typical Video Application
F
will likely result in
F
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is in-
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DRIVING CAPACITIVE LOADS
Capacitive output loading applications will benefit from the
use of a series output resistor R
of a series output resistor, R
put under capacitive loading. Capacitive loads of 5 to 120 pF
are the most critical, causing ringing, frequency response
peaking and possible oscillation. The chart “Frequency Re-
sponse vs. Capacitive Load” give a recommended value for
selecting a series output resistor for mitigating capacitive
loads. The values suggested in the charts are selected for .5
dB or less of peaking in the frequency response. This gives a
good compromise between settling time and bandwidth. For
applications where maximum frequency response is needed
and some peaking is tolerable, the value of R
duced slightly from the recommended values.
FIGURE 5. Decoupling Capacitive Loads
OUT
, to stabilize the amplifier out-
OUT
. Figure 5 shows the use
OUT
can be re-
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