lm6171bi-mwa National Semiconductor Corporation, lm6171bi-mwa Datasheet - Page 17

• Manufacturer Part Number: lm6171bi-mwa
• Description: High Speed Low Power Low Distortion Voltage Feedback Amplifier
• Manufacturer: National Semiconductor Corporation

Application Information
composition-type resistors and mica-type capacitors. Sur-
face mount components are preferred over discrete compo-
nents for minimum inductive effect.
Large values of feedback resistors can couple with parasitic
capacitance and cause undesirable effects such as ringing
or oscillation in high speed amplifiers. For LM6171, a feed-
back resistor of 510Ω gives optimal performance.
COMPENSATION FOR INPUT CAPACITANCE
The combination of an amplifier’s input capacitance with the
gain setting resistors adds a pole that can cause peaking or
oscillation. To solve this problem, a feedback capacitor with
a value
can be used to cancel that pole. For LM6171, a feedback
capacitor of 2 pF is recommended. Figure 1 illustrates the
compensation circuit.
POWER SUPPLY BYPASSING
Bypassing the power supply is necessary to maintain low
power supply impedance across frequency. Both positive
and negative power supplies should be bypassed individu-
ally by placing 0.01 µF ceramic capacitors directly to power
supply pins and 2.2 µF tantalum capacitors close to the
power supply pins.
FIGURE 1. Compensating for Input Capacitance
FIGURE 2. Power Supply Bypassing
C
F
>
(R
G
x C
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IN
)/R
F
(Continued)
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17
TERMINATION
In high frequency applications, reflections occur if signals
are not properly terminated. Figure 3 shows a properly ter-
minated signal while Figure 4 shows an improperly termi-
nated signal.
FIGURE 4. Improperly Terminated Signal
FIGURE 3. Properly Terminated Signal
01233614
01233615
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