LMH6723MF National Semiconductor, LMH6723MF Datasheet - Page 13

• Manufacturer Part Number: LMH6723MF
• Description: OP AMP, 1MA WIDEBAND CFB, POWERWISE
• Manufacturer: National Semiconductor

Specifications of LMH6723MF

• Op Amp Type: Wideband
• No. Of Amplifiers: 1
• Bandwidth: 370MHz
• Slew Rate: 600V/µs
• Supply Voltage Range: 4.5V To 12V
• Amplifier Case Style: SOT-23
• No. Of Pins: 5
• Operating Temperature Range: -40°C To
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Application Section
Both plots show the value of R
required at higher gains to keep R
below the input impedance of the inverting input. This limi-
tation applies to both inverting and non-inverting configura-
tions. For the LMH6723/LMH6724/LMH6725 the input resis-
tance of the inverting input is approximately 500Ω and 100Ω
is a practical lower limit for R
LMH6725 begins to operate in a gain bandwidth limited
fashion in the region where R
gains. Note that the amplifier will operate with R
below 100Ω, however results will be substantially different
than predicted from ideal models. In particular the voltage
potential between the Inverting and Non- Inverting inputs
cannot be expected to remain small.
For inverting configurations the impedance seen by the
source is R
inverting gain since R
of R
the input impedance is equal to 100Ω. Using a termination
resistor this can be brought down to match a 50Ω or 75Ω
source, however, a 150Ω source cannot be matched.
G
is then R
FIGURE 2. RF vs. Non-Inverting Gain
G
FIGURE 3. R
|| R
F
T
/Gain. Thus for an inverting gain of −4 V/V
. For most sources this limits the maximum
F
is determined by Figure 3. The value
F
vs. Inverting Gain
F
F
G
must be increased for higher
. The LMH6723/LMH6724/
versus gain. A higher R
G
(Continued)
from decreasing too far
G
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values well
F
is
13
ACTIVE FILTERS
When using any current feedback Operational Amplifier as
an active filter it is necessary to be careful using reactive
components in the feedback loop. Reducing the feedback
impedance, especially at higher frequencies, will almost cer-
tainly cause stability problems. Likewise capacitance on the
inverting input should be avoided. See Application Notes
OA-7 and OA-26 for more information on Active Filter appli-
cations for Current Feedback Op Amps.
When using the LMH6723/LMH6724/LMH6725 as a low
pass filter the value of R
the value recommended in the R
benefit of reducing R
cies, which improves attenuation 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 con-
figuration reducing R
and is not recommended.
FIGURE 4. Typical Application with Suggested Supply
FIGURE 5. Decoupling Capacitive Loads
F
F
is increased gain at higher frequen-
will likely result in device instability
F
Bypassing
can be substantially reduced from
F
vs. Gain charts. The
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