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參數(shù)資料
| 型號(hào)： | LMC6044 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | CMOS Quad Micropower Operational Amplifier |
| 中文描述： | 微功耗的CMOS四路運(yùn)算放大器 |
| 文件頁數(shù)： | 8/12頁 |
| 文件大?。?/td> | 387K |
| 代理商： | LMC6044 |
Application Hints
(Continued)
nent of the output signal back to the amplifier’s inverting in-
put, thereby preserving phase margin in the overall feedback
loop.
Capacitive load driving capability is enhanced by using a pull
up resistor to V
+
(Figure 3). Typically, a pull up resistor con-
ducting 10 μA or more will significantly improve capacitive
load responses. The value of the pull up resistor must be de-
termined based on the current sinking capability of the ampli-
fier with respect to the desired output swing. Open loop gain
of the amplifier can also be affected by the pull up resistor
(see Electrical Characteristics).
PRINTED-CIRCUIT-BOARD LAYOUT
FOR HIGH-IMPEDANCE WORK
It is generally recognized that any circuit which must operate
with less than 1000 pA of leakage current requires special
layout of the PC board. When one wishes to take advantage
of the ultra-low bias current of the LMC6044, typically less
than 2 fA, it is essential to have an excellent layout. Fortu-
nately, the techniques of obtaining low leakages are quite
simple. First, the user must not ignore the surface leakage of
the PC board, even though it may sometimes appear accept-
ably low, because under conditions of high humidity or dust
or contamination, the surface leakage will be appreciable.
To minimize the effect of any surface leakage, lay out a ring
of foil completely surrounding the LMC6044’s inputs and the
terminals of capacitors, diodes, conductors, resistors, relay
terminals, etc. connected to the op-amp’s inputs, as in Fig-
ure 4 To have a significant effect, guard rings should be
placed on both the top and bottom of the PC board. This PC
foil must then be connected to a voltage which is at the same
voltage as the amplifer inputs, since no leakage current can
flow between two points at the same potential. For example,
a PC board trace-to-pad resistance of 10
12
, which is nor-
mally considered a very large resistance, could leak 5 pA if
the trace were a 5V bus adjacent to the pad of the input. This
would cause a 100 times degradation from the LMC6044’s
actual performance. However, if a guard ring is held within 5
mV of the inputs, then even a resistance of 10
11
would
cause only 0.05 pA of leakage current. See Figure 5 for typi-
cal connections of guard rings for standard op-amp
configurations.
The designer should be aware that when it is inappropriate
to lay out a PC board for the sake of just a few circuits, there
is another technique which is even better than a guard ring
on a PC board: Don’t insert the amplifier’s input pin into the
board at all, but bend it up in the air and use only air as an in-
sulator. Air is an excellent insulator. In this case you may
have to forego some of the advantages of PC board con-
struction, but the advantages are sometimes well worth the
effort
of
using
point-to-point
See Figure 6
up-in-the-air
wiring.
DS011138-18
FIGURE 3. Compensating for Large
Capacitive Loads with a Pull Up Resistor
DS011138-7
FIGURE 4. Example of Guard Ring
in P.C. Board Layout
DS011138-8
Inverting Amplifier
DS011138-10
Non-Inverting Amplifier
DS011138-9
Follower
FIGURE 5. Typical Connections of Guard Rings
www.national.com
8
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| LMC6044AIM | CMOS Quad Micropower Operational Amplifier |
| LMC6044AIN | CMOS Quad Micropower Operational Amplifier |
| LMC6044IM | CMOS Quad Micropower Operational Amplifier |
| LMC6044IN | CMOS Quad Micropower Operational Amplifier |
| LMC6082 | Precision CMOS Dual Operational Amplifier |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LMC6044AIM | 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 |
| LMC6044AIM/NOPB | 功能描述:運(yùn)算放大器 - 運(yùn)放 MicroPwr Quad CMOS 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 |
| LMC6044AIMX | 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 |
| LMC6044AIMX/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 |
| LMC6044AIN | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:CMOS Quad Micropower Operational Amplifier |
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