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參數資料
| 型號： | LMC6484AIM |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 運動控制電子 |
| 英文描述： | CMOS Quad Rail-to-Rail Input and Output Operational Amplifier |
| 中文描述： | QUAD OP-AMP, 1350 uV OFFSET-MAX, 1.5 MHz BAND WIDTH, PDSO14 |
| 封裝： | SOIC-14 |
| 文件頁數： | 14/22頁 |
| 文件大?。?/td> | 973K |
| 代理商： | LMC6484AIM |
Application Information
(Continued)
of the ultra-low input current of the LMC6484, typically less
than 20 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 LMC6484’s inputs and the
terminals of capacitors, diodes, conductors, resistors, relay
terminals, etc. connected to the op-amp’s inputs, as in Fig-
ure 9 To have a significant effect, guard rings should be
placed in 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 amplifier 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 250 times degradation from the LMC6484’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 10 for
typical 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 11
up-in-the-air
wiring.
DS011714-20
FIGURE 9. Example of Guard Ring in P.C. Board
Layout
DS011714-21
Inverting Amplifier
DS011714-22
Non-Inverting Amplifier
DS011714-23
Follower
FIGURE 10. Typical Connections of Guard Rings
DS011714-24
(Input pins are lifted out of PC board and soldered directly to components.
FIGURE 11. Air Wiring
www.national.com
14
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相關代理商/技術參數 |
參數描述 |
|---|---|
| LMC6484AIM | 制造商:Texas Instruments 功能描述:IC OP AMP QUAD CMOS 6484 SOIC14 |
| LMC6484AIM/NOPB | 功能描述:運算放大器 - 運放 CMOS QUAD RRIO OP AMP RoHS:否 制造商:STMicroelectronics 通道數量:4 共模抑制比（最小值）:63 dB 輸入補償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風格:SMD/SMT 封裝 / 箱體:QFN-16 轉換速度:0.89 V/us 關閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| LMC6484AIM/NOPB | 制造商:Texas Instruments 功能描述:Operational Amplifier (Op-Amp) IC |
| LMC6484AIMX | 功能描述:運算放大器 - 運放 RoHS:否 制造商:STMicroelectronics 通道數量:4 共模抑制比（最小值）:63 dB 輸入補償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風格:SMD/SMT 封裝 / 箱體:QFN-16 轉換速度:0.89 V/us 關閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| LMC6484AIMX/NOPB | 功能描述:運算放大器 - 運放 CMOS Quad R/R I/O Op Amp RoHS:否 制造商:STMicroelectronics 通道數量:4 共模抑制比（最小值）:63 dB 輸入補償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風格:SMD/SMT 封裝 / 箱體:QFN-16 轉換速度:0.89 V/us 關閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
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