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參數(shù)資料
| 型號： | AD8571 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | Zero-Drift, Single-Supply, Rail-to-Rail Input/Output Operational Amplifiers |
| 中文描述： | 零漂移，單電源，軌到軌輸入/輸出運算放大器 |
| 文件頁數(shù)： | 15/19頁 |
| 文件大?。?/td> | 247K |
| 代理商： | AD8571 |
AD8571/AD8572/AD8574
–15–
REV. 0
100k
V
AD857x
100k
V
V
SY
= 0V TO 5V
V
OUT
Figure 54b. AD857x Test Circuit for Turn-On Time
APPLICATIONS
A 5 V Precision Strain-Gage Circuit
The extremely low offset voltage of the AD8572 makes it an ideal
amplifier for any application requiring accuracy with high gains,
such as a weigh scale or strain-gage. Figure 55 shows a configuration
for a single supply, precision strain-gage measurement system.
A REF192 provides a 2.5 V precision reference voltage for A2.
The A2 amplifier boosts this voltage to provide a 4.0 V reference
for the top of the strain-gage resistor bridge. Q1 provides the cur-
rent drive for the 350
bridge network. A1 is used to amplify the
output of the bridge with the full-scale output voltage equal to:
(
R
R
B
Where
R
B
is the resistance of the load cell. Using the values given
in Figure 55, the output voltage will linearly vary from 0 V with
no strain to 4 V under full strain.
2
1
2
×
+
)
R
(17)
V
OUT
0V TO 4V
350
V
LOAD
CELL
AD8572-A
R
3
17.4k
V
R
4
100
V
R
1
17.4k
V
R
2
100
V
NOTE:
USE 0.1% TOLERANCE RESISTORS.
20k
V
A1
AD8572-B
REF192
12k
V
1k
V
5V
2.5V
6
4
3
2
4.0V
40mV
FULL-SCALE
Q1
2N2222
OR
EQUIVALENT
A2
Figure 55. A 5 V Precision Strain-Gage Amplifier
3 V Instrumentation Amplifier
The high common-mode rejection, high open-loop gain, and
operation down to 3 V of supply voltage makes the AD857x an
excellent choice of op amp for discrete single supply instrumenta-
tion amplifiers. The common-mode rejection ratio of the AD857x
is greater than 120 dB, but the CMRR of the system is also a
function of the external resistor tolerances. The gain of the differ-
ence amplifier shown in Figure 56 is given as:
V
V
R
+
3
R
R
R
R
V
R
R
OUT
=
+
1
1
2
4
4
1
2
2
1
(18)
V2
V1
V
OUT
R
1
R
3
R
4
R
2
AD857x
IFR
3
R
4
=R
1
R
2
, THEN V
OUT
=R
1
R
2
3
(V1
2
V2)
Figure 56. Using the AD857x as a Difference Amplifier
In an ideal difference amplifier, the ratio of the resistors are set
exactly equal to:
A
R
R
R
R
V
=
=
2
1
4
3
(19)
Which sets the output voltage of the system to:
V
Due to finite component tolerance the ratio between the four
resistors will not be exactly equal, and any mismatch results in a
reduction of common-mode rejection from the system. Referring
to Figure 56, the exact common-mode rejection ratio can be
expressed as:
+
4
2
2
A V
V
OUT
=
)
1
2
(20)
CMRR
R R
R R
4
R R
R R
R R
2
=
+
4
3
3
(21)
In the 3 op amp instrumentation amplifier configuration shown
in Figure 57, the output difference amplifier is set to unity gain
with all four resistors equal in value. If the tolerance of the resis-
tors used in the circuit is given as
δ
, the worst-case CMRR of
the instrumentation amplifier will be:
CMRR
MIN
=
1
2
δ
(22)
V
OUT
R
R
R
R
AD8574-C
V2
R
R
V1
R
G
AD8574-B
AD8574-A
R
TRIM
V
OUT
= 1 +R
G
(V1
2
V2)
Figure 57. A Discrete Instrumentation Amplifier
Configuration
Thus, using 1% tolerance resistors would result in a worst-case
system CMRR of 0.02, or 34 dB. Therefore either high precision
resistors or an additional trimming resistor, as shown in Figure 57,
should be used to achieve high common-mode rejection. The value
of this trimming resistor should be equal to the value of R multi-
plied by its tolerance. For example, using 10 k
resistors with 1%
tolerance would require a series trimming resistor equal to 100
.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| AD8572 | Zero-Drift, Single-Supply, Rail-to-Rail Input/Output Operational Amplifiers |
| AD8572AR | Zero-Drift, Single-Supply, Rail-to-Rail Input/Output Operational Amplifiers |
| AD8572ARU | Zero-Drift, Single-Supply, Rail-to-Rail Input/Output Operational Amplifiers |
| AD8574 | Zero-Drift, Single-Supply, Rail-to-Rail Input/Output Operational Amplifiers |
| AD8574AR | Zero-Drift, Single-Supply, Rail-to-Rail Input/Output Operational Amplifiers |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AD8571_06 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Zero-Drift, Single-Supply, Rail-to-Rail Input/Output Operational Amplifiers |
| AD8571_07 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Zero-Drift, Single-Supply, Rail-to-Rail Input/Output Operational Amplifiers |
| AD8571AR | 制造商:Analog Devices 功能描述:SP Amp Chopper Stabilization Single R-R I/O 5V 8-Pin SOIC N Tube 制造商:Rochester Electronics LLC 功能描述:SINGLE PRECISION RAIL-RAIL CHOPPER OPAMP - Bulk 制造商:Analog Devices 功能描述:OP AMP Z-DRIFT RRI/O 8571 SOIC8 |
| AD8571AR | 制造商:Analog Devices 功能描述:IC SM OP-AMP Z-DRIFT RRI/O ((NW)) |
| AD8571ARM | 制造商:AD 制造商全稱:Analog Devices 功能描述:Zero-Drift, Single-Supply, Rail-to-Rail Input/Output Operational Amplifiers |
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