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| 型号： | LM7131ACMX |
| 厂商： | National Semiconductor |
| 文件页数： | 15/28页 |
| 文件大小： | 0K |
| 描述： | IC OP AMP TINY HS SNG SUPP 8SOIC |
| 标准包装： | 2,500 |
| 放大器类型： | 电压反馈 |
| 电路数： | 1 |
| 转换速率： | 150 V/µs |
| 增益带宽积： | 70MHz |
| -3db带宽： | 90MHz |
| 电流 - 输入偏压： | 20µA |
| 电压 - 输入偏移： | 20µV |
| 电流 - 电源： | 7.5mA |
| 电流 - 输出 / 通道： | 65mA |
| 电压 - 电源，单路/双路(±)： | 2.7 V ~ 12 V，± 2.5 V ~ 6 V |
| 工作温度： | 0°C ~ 70°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-SOIC（0.154"，3.90mm 宽） |
| 供应商设备封装： | 8-SOIC |
| 包装： | 带卷 (TR) |
| 其它名称： | *LM7131ACMX |
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OBSOLETE
SNOS737C – SEPTEMBER 1999 – REVISED APRIL 2013
Overshoot and ringing of the LM7131 can be reduced by adding a small compensation capacitor across the feed
back resistor. For the LM7131 values in pF to tens of pF range are useful initial values. Too large a value will
reduce the circuit bandwidth and degrade pulse response.
Since the small stray capacitance from the circuit layout, other components, and specific circuit bandwidth
requirements will vary, it is often useful to select final values based on prototypes which are similar in layout to
the production circuit boards.
Reflections
The output slew rate of the LM7131 is fast enough to produce reflected signals in many cables and long circuit
traces. For best pulse performance, it may be necessary to terminate cables and long circuit traces with their
characteristic impedance to reduce reflected signals.
Reflections should not be confused with overshoot. Reflections will depend on cable length, while overshoot will
depend on load and feedback resistance and capacitance. When determining the type of problem, often
removing or drastically shortening the cable will reduce or eliminate reflections. Overshoot can exist without a
cable attached to the op amp output.
Driving Flash A/D Converters (Video Converters)
The LM7131 has been optimized to drive flash analog to digital converters in a +5V only system. Different flash
A/D converters have different voltage input ranges. The LM7131 has enough gain-bandwidth product to amplify
standard video level signals to voltages which match the optimum input range of many types of A/D converters.
For example, the popular 1175 type 8-bit flash A/D converter has a preferred input range from 0.6V to 2.6V. If
the input signal has an active video range (excluding sync levels) of approximately 700 mV, a circuit like the one
in Figure 43 can be used to amplify and drive an A/D. The 10
μF capacitor blocks the DC components, and
allows the + input of the LM7131 to be biased through R clamp so that the minimum output is equal to VRB of the
A/D converter. The gain of the circuit is determined as follows:
Output Signal Range = 2.6V (V top) = 0.6V (V bottom) =
2.0V
Gain = Output Signal Range/Input Signal = 2.857 =
2.00/0.700
Gain = (Rf/R1) +1 = (249Ω/133Ω) +1
(1)
R isolation and Cf will be determined by the designer based on the A/D input capacitance and the desired
pulse response of the system. The nominal values of 33
Ω and 5.6 pF shown in the schematic may be a useful
starting point, however, signal levels, A/D converters, and system performance requirements will require
modification of these values.
The isolation resistor, R isolation should be placed close to the output of the LM7131, which should be close to
the A/D input for best results.
R clamp is connected to a voltage level which will result in the bottom of the video signal matching the Vrb level
of the A/D converter. This level will need to be set by clamping the black level of the video signal. The clamp
voltage will depend on the level and polarity of the video signal. Detecting the sync signal can be done by a
circuit such as the LM1881 Video Sync Separator.
NOTE
This is an illustration of a conceptual use of the LM7131, not a complete design. The
circuit designer will need to modify this for input protection, sync, and possibly some type
of gain control for varying signal levels.
Some A/D converters have wide input ranges where the lower reference level can be adjusted. With these
converters, best distortion results are obtained if the lower end of the output range is about 250 mV or more
above the V
input of the LM7131 more. The upper limit can be as high as 4.0V with good results.
22
Copyright 1999–2013, Texas Instruments Incorporated
Product Folder Links: LM7131
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM7131ACN | 制造商:NSC 制造商全称:National Semiconductor 功能描述:IC-HIGH SPEED OP AMP |
| LM7131BCM | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| LM7131BCM5 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Tiny High Speed Single Supply Operational Amplifier |
| LM7131BCM5X | 制造商:Rochester Electronics LLC 功能描述:- Bulk |
| LM7131BCMX | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Tiny High Speed Single Supply Operational Amplifier |
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