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參數(shù)資料
| 型號： | 5962-9453402MCA |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 運(yùn)算放大器 |
| 英文描述： | QUAD OP-AMP, 1.35 uV OFFSET-MAX, 1.15 MHz BAND WIDTH, CDIP14 |
| 封裝： | CERAMIC, DIP-14 |
| 文件頁數(shù)： | 8/26頁 |
| 文件大?。?/td> | 3044K |
| 代理商： | 5962-9453402MCA |
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20160816
FIGURE 7. Pulse Response of LMC6484 Circuit in Figure
5.0 COMPENSATING FOR INPUT CAPACITANCE
It is quite common to use large values of feedback resistance
with amplifiers that have ultra-low input current, like the
LMC6484. Large feedback resistors can react with small val-
ues of input capacitance due to transducers, photodiodes,
and circuit board parasitics to reduce phase margins.
20160819
FIGURE 8. Canceling the Effect of Input Capacitance
The effect of input capacitance can be compensated for by
adding a feedback capacitor. The feedback capacitor (as in
Figure 8 ), C
f, is first estimated by:
or
R
1 CI ≤ R2 Cf
which typically provides significant overcompensation.
Printed circuit board stray capacitance may be larger or small-
er than that of a breadboard, so the actual optimum value for
C
f may be different. The values of Cf should be checked on
the actual circuit. (Refer to the LMC660 quad CMOS amplifier
data sheet for a more detailed discussion.)
6.0 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 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 Figure
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 be-
tween two points at the same potential. For example, a PC
board trace-to-pad resistance of 1012
Ω, which is normally
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 1011
Ω would cause only
0.05 pA of leakage current. See Figure 10 for typical connec-
tions of guard rings for standard op-amp configurations.
20160820
FIGURE 9. Example of Guard Ring in P.C. Board Layout
www.national.com
16
LMC6484QML
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| 5962-9453402QXA | QUAD OP-AMP, 1.35 uV OFFSET-MAX, 1.15 MHz BAND WIDTH, CDSO14 |
| 5962-9453402MCX | QUAD OP-AMP, 3000 uV OFFSET-MAX, 1 MHz BAND WIDTH, CDIP14 |
| 5962-9458101M2X | QUAD OP-AMP, 4000 uV OFFSET-MAX, 4 MHz BAND WIDTH, CQCC20 |
| 5962-9458101MCX | QUAD OP-AMP, 4000 uV OFFSET-MAX, 4 MHz BAND WIDTH, CDIP14 |
| 5962-9459301MPX | OP-AMP, 9000 uV OFFSET-MAX, CDIP8 |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| 5962-9453402QXA | 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 |
| 5962-9454001MPA | 功能描述:電流和電力監(jiān)控器、調(diào)節(jié)器 Fixed 5V CMOS Step Up Switching Reg RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Current Regulators 電源電壓-最大:48 V 電源電壓-最小:5.5 V 工作溫度范圍:- 40 C to + 150 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:HPSO-8 封裝:Reel |
| 5962-9455301M2A | 制造商:Rochester Electronics LLC 功能描述:- Bulk 制造商:Intersil Corporation 功能描述:OP Amp Quad GP 20-Pin CLCC |
| 5962-9455501M3A | 制造商:Texas Instruments 功能描述:Soft Sw PWM Cntrlr 4-OUT PH SHIFT RES 1MHz 28-Pin LCCC Tube 制造商:Texas Instruments 功能描述:SOFT SW PWM CNTRLR QUAD-OUT PH SHIFT RES 1MHZ 28LCCC - Rail/Tube |
| 5962-9455501MRA | 制造商:Texas Instruments 功能描述:Soft Sw PWM Cntrlr 4-OUT PH SHIFT RES 1MHz 20-Pin CDIP Tube 制造商:Texas Instruments 功能描述:SOFT SW PWM CNTRLR 4-OUT PH SHIFT RES 1MHZ 20CDIP - Rail/Tube |
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