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參數(shù)資料
| 型號： | AN-242 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | LJT 18C 18#20 SKT RECP |
| 中文描述： | 應(yīng)用新的精密運(yùn)算放大器 |
| 文件頁數(shù)： | 13/16頁 |
| 文件大?。?/td> | 267K |
| 代理商： | AN-242 |
As can be seen inFigure 22, connecting the input amplifiers
as followers simplifies the circuit considerably. But single
resistor gain control is no longer available and maximum
bandwidth is less with all the gain developed by A3. Resistor
matching is more critical for a given common-mode rejec-
tion, but AC matching of the input amplifier is less a prob-
lem. Another method of trimming AC common-mode rejec-
tion is shown here.
integrator reset
When pursuing the ultimate in performance with the LM11, it
becomes evident that components other than the op amp
can limit performance. This can be the case when semicon-
ductor switches are used. Their leakage easily exceeds the
bias current when elevated temperatures are involved.
The integrator with electrical reset inFigure 23 gives a solu-
tion to this problem. Two switches in series are used to
shunt the integrating capacitor. In the off state, one switch,
Q2, disconnects the output while the other, Q1, isolates the
leakage of the first. This leakage is absorbed by R3. Only
the op amp offset appears across the junctions of Q1, so its
leakage is reduced by two orders of magnitude.
A junction FET could be used for Q1 but not for Q2 because
there is no equivalent to the enhancement mode MOSFET.
The gate of a JFET must be reverse biased to turn it off and
leakage on its output cannot be avoided.
MOS switches with gate-protection diodes are preferred in
production situations as they are less sensitive to damage
from static charges in handling. If used, D1 and R2 should
be inlcuded to remove bias from the internal protection di-
ode when the switch is off.
*
polystyrene recommended
2
required if protected-
gate switch is used
TL/H/7479–25
Figure 23. Reset is provided for this inegrator and
switch leakage is isolated from the summing
junction. Greater precision can be provided if
bias-current compensation is included.
R1
e
R3; R2
e
R4
A
V
e
R2
R1
2
trim for DC CMRR
3
set for AC CMRR
TL/H/7479–24
Figure 22. For moderate-gain instrumentation amplifiers, input amplifiers can be connected as followers. This simpli-
fies circuitry, but A3 must also have low drift.
13
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PDF描述 |
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| AN-40 | Application Note 40 |
| AN-5002 | LJT 18C 18#20 SKT WALL RECP |
| AN-5025 | Applications Using the GTLP10B320 |
| AN-5026 | Circular Connector; No. of Contacts:19; Series:MS27656; Body Material:Aluminum; Connecting Termination:Crimp; Connector Shell Size:15; Circular Contact Gender:Pin; Circular Shell Style:Wall Mount Receptacle; Insert Arrangement:15-19 RoHS Compliant: No |
| AN-5031 | GTLP Power Configuration |
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