LM7171AMJ-QML National Semiconductor, LM7171AMJ-QML Datasheet - Page 12

• Manufacturer Part Number: LM7171AMJ-QML
• Description: Very High Speed/ High Output Current/ Voltage Feedback Amplifier
• Manufacturer: National Semiconductor

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Typical Performance Characteristics
Harmonic Distortion
vs Frequency
Note 13: The THD measurement at low frequency is limited by the test instrument.
Simplified Schematic Diagram
Note: M1 and M2 are current mirrors.
Application Notes
LM7171 Performance Discussion
The LM7171 is a very high speed, voltage feedback ampli-
fier. It consumes only 6.5 mA supply current while providing
a unity-gain bandwidth of 200 MHz and a slew rate of 4100V/
µs. It also has other great features such as low differential
gain and phase and high output current.
The LM7171 is a true voltage feedback amplifier. Unlike cur-
rent feedback amplifiers (CFAs) with a low inverting input im-
pedance and a high non-inverting input impedance, both in-
puts of voltage feedback amplifiers (VFAs) have high
impedance nodes. The low impedance inverting input in
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Harmonic Distortion
vs Frequency
unless otherwise noted, T
12
CFAs and a feedback capacitor create an additional pole
that will lead to instability. As a result, CFAs cannot be used
in traditional op amp circuits such as photodiode amplifiers,
I-to-V converters and integrators where a feedback capacitor
is required.
LM7171 Circuit Operation
The class AB input stage in LM7171 is fully symmetrical and
has a similar slewing characteristic to the current feedback
amplifiers. In the LM7171 Simplified Schematic, Q1 through
Q4 form the equivalent of the current feedback input buffer,
R
E
the equivalent of the feedback resistor, and stage A buff-
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Maximum Power Dissipation
vs Ambient Temperature
A
= 25˚C (Continued)
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