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參數(shù)資料
| 型號： | OP227 |
| 廠商： | Analog Devices, Inc. |
| 元件分類： | 運(yùn)動控制電子 |
| 英文描述： | Dual, Low Noise, Low Offset Instrumentation Operational Amplifier |
| 中文描述： | 雙通道，低噪聲，低失調(diào)儀表運(yùn)算放大器 |
| 文件頁數(shù)： | 12/16頁 |
| 文件大?。?/td> | 481K |
| 代理商： | OP227 |
REV. A
OP227
–12–
The differential gain A
d
is 1 + 2R1/R0 and the common-mode
input V
CM
is rejected.
While output error due to input offsets and noise are easily
determined, the effects of finite gain and common-mode rejec-
tion are more subtle. CMR of the complete instrumentation
amplifier is directly proportioned to the match in CMR of the
input op amps. This match varies from 97 dB to 110 dB mini-
mum for the OP227. Using 100 dB, then the output response to
a common-mode input V
CM
would be:
[
CMRR of the instrumentation amplifier, which is defined as
20 log10A
d
/A
CM
, is simply equal to the CMRR of the OP227.
While this CMRR is already high, overall CMRR of the
complete amplifier can be raised by trimming the output stage
resistor network.
Finite gain of the input op amps causes a scale factor error and a
small degradation in CMR. Designating the open-loop gain of
op amp A
1
as A
O1
, and op amp A
2
as A
O2
, then the following
equation approximates output:
V
A V
O
CM
CM
]
=
￥
10
5
–
V
R
R
A
A
A V
R
R
A
A
V
O
O
O
d
O
O
CM
1
1
1
0
1
1
2 1
0
1
1
1
2
1
2
+
+
ê
á
ˉ
+
ê
á
ˉ
ê
á
ˉ
–
This can be simplified by defining A
O
as the nominal open-loop
gain and A0 as the differential open-loop gain. Then:
V
R
R
A
A V
R
R
A
A
V
O
O
d
O
2
O
CM
1
1
0
1
1
2 1
0
+
+
ê
á
ˉ
D
The high open-loop gain of each amplifier within the OP227
(700,000 minimum at 25
∞
C in R
L
≥
2 k
W
) assures good gain
accuracy even at high values of A
d
. The effect of finite open-
loop gain on CMR can be approximated by:
CMRR
A
D
A
O
O
2
If A
O
/A
O
were 6% and A
O
were 600,000, then the CMRR due to
finite gain of the input op amps would be approximately 140 dB.
R1
R1
R2
R2
A3
A1
A2
R2
R0
V
CM
– 1/2V
d
V
CM
+ 1/2V
d
V1
V2
1/2
OP227
V
O
OP27
V
O
= (1 +
2R1
) Vd
R0
R2
1/2
OP227
Figure 4. Three Op Amp Instrumentation Amplifier Using
OP227 and OP27
The unity-gain output stage contributes negligible error to the
overall amplifier. However, matching of the four resistor R2
network is critical to achieving high CMR. Consider a worst-
case situation where each R2 resistor had an error of
±
R2. If
the resistor ratio is high on one side and low on the other, then
the common-mode gain will be 2 R2/2 R2. Since the output
stage gain is unity, CMRR will then be R2/2 R2. It is common
practice to maximize overall CMRR for the total instrumenta-
tion amplifier circuit.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| OP227E | Analog IC |
| OP227F | Analog IC |
| OP227G | Analog IC |
| OP227AYMDA | Dual, Low Noise, Low Offset Instrumentation Operational Amplifier |
| OP227EY | Dual, Low Noise, Low Offset Instrumentation Operational Amplifier |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| OP-227 | 制造商:AD 制造商全稱:Analog Devices 功能描述:DUAL, LOW-NOISE LOW OFFSET INSTRUMENTATION OPERATIONAL AMPLIFIER |
| OP-227A883 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:MICROCIRCUIT, LINEAR, LOW NOISE OPERATIONAL AMPLIFIER, MONOLITHIC SILICON |
| OP-227AJ | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:Voltage-Feedback Operational Amplifier |
| OP227AJ/883C | 制造商:Linear Technology 功能描述:IC,OP-AMP,DUAL,BIPOLAR,DIP,14PIN,CERAMIC |
| OP227AJ883B | 制造商:Linear Technology 功能描述:AMPLIFIER-OP AMP |
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