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參數(shù)資料
| 型號(hào)： | LMV710 |
| 廠商： | National Semiconductor Corporation |
| 元件分類： | 運(yùn)算放大器 |
| 英文描述： | Low Power, RRIO Operational Amplifiers with High Output Current Drive and Shutdown Option |
| 中文描述： | 低功耗，RRIO運(yùn)算放大器具有高輸出電流驅(qū)動(dòng)和關(guān)機(jī)選項(xiàng) |
| 文件頁數(shù)： | 12/19頁 |
| 文件大小： | 708K |
| 代理商： | LMV710 |
Application Note
(Continued)
4.0 COMPENSATION OF INPUT CAPACITANCE
In the application (
Figure 4
) where a large feedback resistor
is used, the feedback resistor can react with the input ca-
pacitance of the op amp and introduce an additional pole to
the close loop frequency response.
This pole occurs at frequency f
p
, where
Any stray capacitance due to external circuit board layout,
any source capacitance from transducer or photodiode con-
nected to the summing node will also be added to the input
capacitance. If f
p
is less than or close to the unity-gain
bandwidth (5MHz) of the op amp, the phase margin of the
loop is reduced and can cause the system to be unstable.
To avoid this problem, make sure that f
p
occurs at least 2
octaves beyond the expected 3dB frequency corner of the
close loop frequency response. If not, a feedback capacitor
C
F
can be placed in parallel with R
F
such that
The paralleled R
F
and C
F
introduce a zero, which cancels
the effect from the pole.
5.0 CAPACITIVE LOAD TOLERANCE
The LMV710, LMV711 and LMV715 can directly drive 200pF
in unity-gain without oscillation. The unity-gain follower is the
most sensitive configuration to capacitive loading. Direct
capacitive loading reduces the phase margin of amplifiers.
The combination of the amplifier’s output impedance and the
capacitive load induces phase lag. This results in either an
underdamped pulse response or oscillation. To drive a
heavier capacitive load, circuit in
Figure 5
can be used.
In
Figure 5
, the isolation resistor R
ISO
and the load capacitor
C
L
form a pole to increase stability by adding more phase
margin to the overall system. The desired performance de-
pends on the value of R
ISO
. The bigger the R
ISO
resistor
value, the more stable V
OUT
will be. But the DC accuracy is
not great when the R
resistor in
Figure 5
, the output would be voltage divided by
R
ISO
and the load resistor.
The circuit in
Figure 6
is an improvement to the one in
Figure
5
because it provides DC accuracy as well as AC stability. In
this circuit, R
provides the DC accuracy by using feed-
forward techniques to connect V
to R
. C
and R
serve
to counteract the loss of phase margin by feeding the high
frequency component of the output signal back to the ampli-
fier’s inverting input, thereby preserving phase margin in the
overall feedback loop. Increased capacitive drive is possible
by increasing the value of C
F
. This in turn will slow down the
pulse response.
6.0 APPLICATION CIRCUITS
PEAK DETECTOR
Peak detectors are used in many applications, such as test
equipment, measurement instrumentation, ultrasonic alarm
systems, etc.
Figure 7
shows the schematic diagram of a
peak detector using LMV710 or LMV711 or LMV715. This
peak detector basically consists of a clipper, a parallel RC
network, and a voltage follower.
10132518
FIGURE 4. Cancelling the Effect of Input Capacitance
10132521
FIGURE 5. Indirectly Driving A Capacitive Load using
Resistive Isolation
10132522
FIGURE 6. Indirectly Driving A Capacitive A Load with
DC Accuracy
L
www.national.com
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LMV710IDBVR | 功能描述:運(yùn)算放大器 - 運(yùn)放 Sngl Lo-Pwr RRIO Hi Out Crnt Drv/Shtdwn 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 |
| LMV710IDBVRE4 | 功能描述:運(yùn)算放大器 - 運(yùn)放 Sngl Lo-Pwr RRIO Hi Out Crnt Drv/Shtdwn 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 |
| LMV710IDBVRG4 | 功能描述:運(yùn)算放大器 - 運(yùn)放 Sgl Low-Pwr RRIO Op 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 |
| LMV710IDCKR | 功能描述:運(yùn)算放大器 - 運(yùn)放 Sngl Lo-Pwr RRIO Hi Out Crnt Drv/Shtdwn 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 |
| LMV710IDCKRE4 | 功能描述:運(yùn)算放大器 - 運(yùn)放 Sngl Lo-Pwr RRIO Hi Out Crnt Drv/Shtdwn 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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