Datasheet

LM6181
www.ti.com SNOS634B –MAY 1998–REVISED MAY 2013
Variation of Closed Loop Gain
from −1 to −5 Yields Similar Responses
Figure 78.
The closed-loop bandwidth of the LM6181 depends on the feedback resistance, R
f
. Therefore, R
S
and not R
f
,
must be varied to adjust for the desired closed-loop gain as in Figure 79.
Figure 79. R
S
Is Adjusted to Obtain
the Desired Closed Loop Gain, A
VCL
POWER SUPPLY BYPASSING AND LAYOUT
CONSIDERATIONS
A fundamental requirement for high-speed amplifier design is adequate bypassing of the power supply. It is
critical to maintain a wideband low-impedance to ground at the amplifiers supply pins to insure the fidelity of high
speed amplifier transient signals. 10 μF tantalum and 0.1 μF ceramic bypass capacitors are recommended for
each supply pin. The bypass capacitors should be placed as close to the amplifier pins as possible (0.5″ or less).
FEEDBACK RESISTOR SELECTION: R
f
Selecting the feedback resistor, R
f
, is a dominant factor in compensating the LM6181. For general applications
the LM6181 will maintain specified performance with an 820Ω feedback resistor. Although this value will provide
good results for most applications, it may be advantageous to adjust this value slightly. Consider, for instance,
the effect on pulse responses with two different configurations where both the closed-loop gains are 2 and the
feedback resistors are 820Ω and 1640Ω, respectively. Figure 80 and Figure 81 illustrate the effect of increasing
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