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參數(shù)資料
| 型號： | LM6181 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | 100 mA, 100 MHz Current Feedback Amplifier |
| 中文描述： | 一〇 〇毫安，100 MHz電流反饋放大器 |
| 文件頁數(shù)： | 16/23頁 |
| 文件大?。?/td> | 1848K |
| 代理商： | LM6181 |
Typical Applications
CURRENT FEEDBACK TOPOLOGY
For a conventional voltage feedback amplifier the resulting
small-signal bandwidth is inversely proportional to the de-
sired gain to a first order approximation based on the
gain-bandwidth concept. In contrast, the current feedback
amplifier topology, such as the LM6181, transcends this limi-
tation to offer a signal bandwidth that is relatively indepen-
dent of the closed-loop gain. Figure 1a and Figure 1b illus-
trate that for closed loop gains of 1 and 5 the resulting
pulse fidelity suggests quite similar bandwidths for both
configurations.
The closed-loop bandwidth of the LM6181 depends on the
feedback resistance, R
. Therefore, R
and not R
, must be
varied to adjust for the desired closed-loop gain as in Figure
2
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 ampli-
fiers 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 by-
pass 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
, is a dominant factor in
compensating the LM6181. For general applications the
LM6181 will maintain specified performance with an 820
feedback resistor. Although this value will provide good re-
sults 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 820
and 1640
, respectively. Figure 3a and Figure 3b illustrate
the effect of increasing R
while maintaining the same
closed-loop gain— the amplifier bandwidth decreases. Ac-
cordingly, larger feedback resistors can be used to slow
down the LM6181 (see 3 dB bandwidth vs R
typical curves)
and reduce overshoot in the time domain response. Con-
versely, smaller feedback resistance values than 820
can
be used to compensate for the reduction of bandwidth at
high closed loop gains, due to 2nd order effects. For ex-
ample Figure 4 illustrates reducing R
to 500
to establish
the desired small signal response in an amplifier configured
for a closed loop gain of 25.
DS011328-12
1a
DS011328-13
1b
FIGURE 1. 1a, 1b: Variation of Closed Loop Gain
from 1 to 5 Yields Similar Responses
DS011328-14
FIGURE 2. R
Is Adjusted to Obtain
the Desired Closed Loop Gain, A
VCL
www.national.com
16
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM6181AIM | 制造商:Texas Instruments 功能描述: |
| LM6181AIM-8 | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| LM6181AIN | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:100 mA, 100 MHz Current Feedback Amplifier |
| LM6181AJM | 制造商:Texas Instruments 功能描述: |
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