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參數(shù)資料
| 型號(hào)： | LMH6720 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | Wideband Video Op Amp; Single, Single with Shutdown and Quad |
| 中文描述： | 寬帶視頻運(yùn)算放大器，單，單與關(guān)機(jī)和四 |
| 文件頁數(shù)： | 9/15頁 |
| 文件大?。?/td> | 597K |
| 代理商： | LMH6720 |
Application Section
FEEDBACK RESISTOR SELECTION
One of the key benefits of a current feedback operational
amplifier is the ability to maintain optimum frequency re-
sponse independent of gain by using appropriate values for
the feedback resistor (R
F
). The Electrical Characteristics and
Typical Performance plots specify an R
F
of 300
, a gain of
+2V/V and
±
5V power supplies (unless otherwise specified).
Generally, lowering R
F
from it’s recommended value will
peak the frequency response and extend the bandwidth
while increasing the value of R
F
will cause the frequency
response to roll off faster. Reducing the value of R
F
too far
below it’s recommended value will cause overshoot, ringing
and, eventually, oscillation.
The plot labeled "Frequency Response vs. R
" shows the
LMH6714/6720/6722’s frequency response as R
F
is varied
(R
= 100
, A
= +2). This plot shows that an R
of 147
results in peaking. An R
of 300
gives near maximal band-
width and gain flatness with good stability. An R
of 400
gives excellent stability with only a small bandwidth penalty.
Since all applications are slightly different it is worth some
experimentation to find the optimal R
F
for a given circuit.
Note that it is not possible to use a current feedback amplifier
with the output shorted directly to the inverting input. The
buffer configuration of the LMH6714/6720/6722 requires a
600
feedback resistor for stable operation.
For more information see Application Note OA-13 which
describes the relationship between R
and closed-loop fre-
quency response for current feedback operational amplifiers.
The value for the inverting input impedance for the
LMH6714/6720/6722 is approximately 180
. The LMH6714/
6720/6722 is designed for optimum performance at gains of
+1 to +6 V/V and 1 to 5V/V. When using gains of
±
7V/V or
more the low values of R
G
required will make inverting input
impedances very low.
When configuring the LMH6714/6720/6722 for gains other
than +2V/V, it is usually necessary to adjust the value of the
feedback resistor. The two plots labeled “R
vs. Non-
inverting Gain” and “R
vs. Inverting Gain” provide recom-
mended feedback resistor values for a number of gain se-
lections.
In the “R
vs. Non-Inverting Gain” and the “R
vs. Inverting
Gain” charts the recommended value of R
is depicted by
the solid line, which starts high, decreases to 200
and
begins increasing again. The reason that a higher R
is
required at higher gains is the need to keep R
G
from de-
creasing too far below the output impedance of the input
buffer. For the LMH6714/6720/6722 the output resistance of
the input buffer is approximately 180
and 50
is a practical
lower limit for R
G
. Due to the limitations on R
G
the LMH6714/
6720/6722 begins to operate in a gain bandwidth limited
fashion for gains of
±
5V/V or greater.
ACTIVE FILTERS
When using any current feedback Operational Amplifier as
an active filter it is important to be very careful when using
reactive components in the feedback loop. Anything that
reduces the impedance of the negative feedback, especially
at higher frequencies, will almost certainly cause stability
problems. Likewise capacitance on the inverting input needs
20056512
FIGURE 1. Frequency Response vs. R
F
20056515
FIGURE 2. R
F
vs. Non-Inverting Gain
20056514
FIGURE 3. R
F
vs. Inverting Gain
L
www.national.com
9
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參數(shù)描述 |
|---|---|
| LMH6720J-QML | 制造商:Texas Instruments 功能描述: |
| LMH6720MA | 功能描述:運(yùn)算放大器 - 運(yùn)放 RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補(bǔ)償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| LMH6720MA/NOPB | 功能描述:運(yùn)算放大器 - 運(yùn)放 Sgl 600Mhz Video Amp RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補(bǔ)償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| LMH6720MAX | 功能描述:運(yùn)算放大器 - 運(yùn)放 RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補(bǔ)償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| LMH6720MAX/NOPB | 功能描述:運(yùn)算放大器 - 運(yùn)放 RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補(bǔ)償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
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