參數(shù)資料
型號(hào): LMC6001AIH
廠商: NATIONAL SEMICONDUCTOR CORP
元件分類(lèi): 運(yùn)算放大器
英文描述: JT 11C 11#16 PIN PLUG
中文描述: OP-AMP, 700 uV OFFSET-MAX, 1.3 MHz BAND WIDTH, MBCY8
封裝: METAL, CAN-8
文件頁(yè)數(shù): 9/14頁(yè)
文件大?。?/td> 305K
代理商: LMC6001AIH
Applications Hints
(Continued)
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 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 500 times degradation from the
LMC6001’s actual performance. If a guard ring is used and
held within 1 mV of the inputs, then the same resistance of
10
12
will only cause 10 fA of leakage current. Even this
small amount of leakage will degrade the extremely low input
current performance of the LMC6001. 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 up-in-the-air wiring. See Figure
6
Another potential source of leakage that might be over-
looked is the device package. When the LMC6001 is manu-
factured, the device is always handled with conductive finger
cots. This is to assure that salts and skin oils do not cause
leakage paths on the surface of the package. We recom-
mend that these same precautions be adhered to, during all
phases of inspection, test and assembly.
Latchup
CMOS devices tend to be susceptible to latchup due to their
internal parasitic SCR effects. The (I/O) input and output pins
look similar to the gate of the SCR. There is a minimum cur-
rent required to trigger the SCR gate lead. The LMC6001 is
designed to withstand 100 mA surge current on the I/O pins.
Some resistive method should be used to isolate any capaci-
tance from supplying excess current to the I/O pins. In addi-
tion, like an SCR, there is a minimum holding current for any
latchup mode. Limiting current to the supply pins will also in-
hibit latchup susceptibility.
Typical Applications
The extremely high input resistance, and low power con-
sumption, of the LMC6001 make it ideal for applications that
require battery-powered instrumentation amplifiers. Ex-
amples of these types of applications are hand-held pH
probes, analytic medical instruments, electrostatic field de-
tectors and gas chromotographs.
Two Opamp, Temperature
Compensated pH Probe Amplifier
The signal from a pH probe has a typical resistance between
10 M
and 1000 M
. Because of this high value, it is very
important that the amplifier input currents be as small as
possible. The LMC6001 with less than 25 fA input current is
an ideal choice for this application.
The theoretical output of the standard Ag/AgCl pH probe is
59.16 mV/pH at 25C with 0V out at a pH of 7.00. This output
is proportional to absolute temperature. To compensate for
this, a temperature compensating resistor, R1, is placed in
DS011887-8
FIGURE 4. Examples of Guard
Ring in PC Board Layout
DS011887-9
Inverting Amplifier
DS011887-10
Non-Inverting Amplifier
DS011887-11
Follower
FIGURE 5. Typical Connections of Guard Rings
DS011887-12
(Input pins are lifted out of PC board and soldered directly to components.
FIGURE 6. Air Wiring
www.national.com
9
相關(guān)PDF資料
PDF描述
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LMC6001AIN 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
LMC6001AIN/NOPB 功能描述:運(yùn)算放大器 - 運(yùn)放 ULTRA ULTRA-LOW INPUT CURRENT 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
LMC6001AIN/NOPB 制造商:Texas Instruments 功能描述:Operational Amplifier (Op-Amp) IC
LMC6001BIH 制造商:Rochester Electronics LLC 功能描述:- Bulk
LMC6001BIN 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