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參數(shù)資料
| 型號(hào)： | LMV982 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | 1.8V, RRIO Operational Amplifiers with Shutdown |
| 中文描述： | 1.8，RRIO運(yùn)算放大器，帶有關(guān)斷 |
| 文件頁(yè)數(shù)： | 13/18頁(yè) |
| 文件大?。?/td> | 585K |
| 代理商： | LMV982 |
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Application Note
1.0 INPUT AND OUTPUT STAGE
The rail-to-rail input stage of this family provides more flex-
ibility for the designer. The LMV981/LMV982 use a compli-
mentary PNP and NPN input stage in which the PNP stage
senses common mode voltage near V
and the NPN stage
senses common mode voltage near V
+
. The transition from
the PNP stage to NPN stage occurs 1V below V
+
. Since both
input stages have their own offset voltage, the offset of the
amplifier becomes a function of the input common mode
voltage and has a crossover point at 1V below V
+
.
This V
OS
crossover point can create problems for both DC
and AC coupled signals if proper care is not taken. Large
input signals that include the V
crossover point will cause
distortion in the output signal. One way to avoid such distor-
tion is to keep the signal away from the crossover. For
example, in a unity gain buffer configuration and with V
=
5V, a 5V peak-to-peak signal will contain input-crossover
distortion while a 3V peak-to-peak signal centered at 1.5V
will not contain input-crossover distortion as it avoids the
crossover point. Another way to avoid large signal distortion
is to use a gain of 1 circuit which avoids any voltage
excursions at the input terminals of the amplifier. In that
circuit, the common mode DC voltage can be set at a level
away from the V
OS
cross-over point. For small signals, this
transition in V
shows up as a V
dependent spurious
signal in series with the input signal and can effectively
degrade small signal parameters such as gain and common
mode rejection ratio. To resolve this problem, the small
signal should be placed such that it avoids the V
cross-
over point. In addition to the rail-to-rail performance, the
output stage can provide enough output current to drive
600
loads. Because of the high current capability, care
should be taken not to exceed the 150C maximum junction
temperature specification.
2.0 SHUTDOWN MODE
The LMV981/LMV982 have a shutdown pin. To conserve
battery life in portable applications, the LMV981/LMV982
can be disabled when the shutdown pin voltage is pulled low.
The shutdown pin can’t be left unconnected. In case shut-
down operation is not needed, the shutdown pin should be
connected to V
+
when the LMV981/LMV982 are used. Leav-
ing the shutdown pin floating will result in an undefined
operation mode, either shutdown or active, or even oscillat-
ing between the two modes.
3.0 INPUT BIAS CURRENT CONSIDERATION
The LMV981/LMV982 family has a complementary bipolar
input stage. The typical input bias current (I
) is 15nA. The
input bias current can develop a significant offset voltage.
This offset is primarily due to I
flowing through the negative
feedback resistor, R
. For example, if I
is 50nA and R
is
100k
, then an offset voltage of 5mV will develop (V
= I
B
x R
). Using a compensation resistor (R
), as shown in
Figure 1
, cancels this effect. But the input offset current (I
)
will still contribute to an offset voltage in the same manner.
Typical Applications
4.0 HIGH SIDE CURRENT SENSING
The high side current sensing circuit (
Figure 2
) is commonly
used in a battery charger to monitor charging current to
prevent over charging.Asense resistor R
is connected
to the battery directly. This system requires an op amp with
rail-to-rail input. The LMV981/LMV982 are ideal for this ap-
plication because the common mode input range goes up to
the rail.
20021459
FIGURE 1. Canceling the Offset Voltage due to Input
Bias Current
200214H0
FIGURE 2. High Side Current Sensing
L
www.national.com
13
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LMV982DMR2G | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:Single and Dual Low Voltage, Rail-to-Rail Input and Output, Operational Amplifiers with Shutdown |
| LMV982IDGSR | 功能描述:運(yùn)算放大器 - 運(yùn)放 Dual 1.8V w/R-to-R I/O & Shutdown 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 |
| LMV982IDGSRE4 | 功能描述:運(yùn)算放大器 - 運(yùn)放 Dual 1.8V w/R-to-R I/O & Shutdown 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 |
| LMV982IDGSRG4 | 功能描述:運(yùn)算放大器 - 運(yùn)放 Dual 1.8V w/R-to-R I/O & Shutdown 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 |
| LMV982IDGST | 制造商:TI 制造商全稱:Texas Instruments 功能描述:1.8-V OPERATIONAL AMPLIFIERS WITH RAIL-TO-RAIL AND OUTPUT AND SHUTDOWN |
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