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參數(shù)資料
| 型號(hào)： | LMH6658 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | 270MHz Single Supply, Single & Dual Amplifiers |
| 中文描述： | 270MHz單電源，單 |
| 文件頁(yè)數(shù)： | 15/20頁(yè) |
| 文件大小： | 788K |
| 代理商： | LMH6658 |
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Application Section
LARGE SIGNAL BEHAVIOR
The LMH6657/6658 is specially designed to handle large
output swings, such as those encountered in video wave-
forms, without being slew rate limited. With 5V supply, the
LMH6657/6658 slew rate limit is larger than that might be
necessary to make full allowable output swing excursions.
Therefore, the large signal frequency response is dominated
by the small signal characteristics, rather than the conven-
tional limitation imposed by slew rate limit.
The LMH6657/6658 input stage is designed to provide ex-
cess overdrive when needed. This occurs when fast input
signal excursions cannot be followed by the output stage. In
these situations, the device encounters larger input signals
than would be encountered under normal closed loop con-
ditions. The LMH6657/6658 input stage is designed to take
advantage of this "input overdrive" condition. The larger the
amount of this overdrive, the greater is the speed with which
the output voltage can change. Here is a plot of how the
output slew rate limitation varies with respect to the amount
of overdrive imposed on the input:
To relate the explanation above to a practical example,
consider the following application example. Consider the
case of a closed loop amplifier with a gain of 1 amplifying a
sinusoidal waveform. From the plot of Output vs. Input (Typi-
cal Performance Characteristics section), with a 30MHz sig-
nal and 7V
input signal, it can be seen that the output will
be limited to a swing of 6.9V
. From the frequency Re-
sponse plot it can be seen that the inverting gain of 1 has a
32 output phase shift at this frequency. It can be shown
that this setup will result in about 1.9V
differential input
voltage corresponding to 650V/μs of slew rate from
Figure 1
,
above (SR = V
O
(pp)*
π
*f = 650V/μs). Note that the amount of
overdrive appearing on the input for a given sinusoidal test
waveform is affected by the following:
Output swing
Gain setting
Input/output phase relationship for the given test fre-
quency
Amplifier configuration (inverting or non-inverting)
Due to the higher frequency phase shift between input and
output, there is no closed form solution to input overdrive for
a given input. Therefore,
Figure 1
is not very useful by itself
in determining the output swing.
The following plots aid in predicting the output transition time
based on the amount of swing required for a given gain
setting.
Beyond a gain of 5 or so, the LMH6657/6658 output transi-
tion would be limited by bandwidth. For example, with a gain
of 5, the 3dB BW would be around 30MHz corresponding to
a rise time of about 12ns (10% - 90%). Assuming a near
linear transition, the 20%-80% transition time would be
around 9ns which matches the measured results as shown
in
Figure 2
.
When the output is heavily loaded, output swing may be
limited by current capability of the device. Refer to "Output
Current Capability" section, below, for more details.
20053250
FIGURE 1. Plot Showing the Relationship Between
Slew Rate and Input Overdrive
20053251
FIGURE 2. Output 20%-80% Transition vs. Output
Voltage Swing (Non-Inverting Gain)
20053252
FIGURE 3. Output 20%-80% Transition vs. Output
Voltage Swing (Inverting Gain)
L
www.national.com
15
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| LMH6658MA | 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 |
| LMH6658MA/NOPB | 功能描述:運(yùn)算放大器 - 運(yùn)放 Dual 3V 270MhzAmp 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 |
| LMH6658MAX | 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 |
| LMH6658MAX/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 |
| LMH6658MM | 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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