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參數(shù)資料
| 型號(hào)： | OP493 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | Precision, Micropower Operational Amplifiers(精密的微功率四運(yùn)放) |
| 中文描述： | 精密，微功耗運(yùn)算放大器（精密的微功率四運(yùn)放） |
| 文件頁(yè)數(shù)： | 12/16頁(yè) |
| 文件大小： | 273K |
| 代理商： | OP493 |
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REV. A
–12–
OP193/OP293/OP493
A Single-Supply Instrumentation Amplifier
Designing a true single-supply instrumentation amplifier with
zero-input and zero-output operation requires special care. T he
traditional configuration, shown in Figure 31, depends upon
amplifier A1’s output being at 0 V when the applied common-
mode input voltage is at 0 V. Any error at the output is multi-
plied by the gain of A2. In addition, current flows through
resistor R3 as A2’s output voltage increases. A1’s output must
remain at 0 V while sinking the current through R3, or a gain
error will result. With a maximum output voltage of 4 V, the
current through R3 is only 2
μ
A, but this will still produce an
appreciable error.
+5V
V+
V–
+5V
V+
V–
V
OUT
R4
1.98M
R3
20k
R2
1.98M
R1
20k
I
SINK
–IN
+IN
1/2 OP293
A2
1/2 OP293
A1
Figure 31. A Conventional Instrumentation Amplifier
One solution to this problem is to use a pull-down resistor. For
example, if R3 = 20 k
, then the pull-down resistor must be
less than 400
. However, the pull-down resistor appears as a
fixed load when a common-mode voltage is applied. With a 4 V
common-mode voltage, the additional load current will be 10 mA,
which is unacceptable in a low power application.
Figure 32 shows a better solution. A1’s sink current is provided
by a pair of N-channel FET transistors, configured as a current
mirror. With the values shown, sink current of Q2 is about
340
μ
A. T hus, with a common-mode voltage of 4 V, the addi-
tional load current is limited to 340
μ
A versus 10 mA with a
400
resistor.
+5V
V+
V–
+5V
V+
V–
V
OUT
+IN
1/2 OP293
A2
R4
1.98M
R3
20k
R2
1.98M
R1
20k
–IN
1/2 OP293
A1
+5V
10k
Q1
Q2
VN2222
Figure 32. An Improved Single-Supply, 0 V
IN
, 0 V
OUT
Instrumentation Amplifier
A Low-Power, T emperature to 4–20 mA T ransmitter
A simple temperature to 4–20 mA transmitter is shown in Fig-
ure 33. After calibration, this transmitter is accurate to
±
0.5
°
C
over the –50
°
C to +150
°
C temperature range. T he transmitter
operates from +8 V to +40 V with supply rejection better than
3 ppm/V. One half of the OP293 is used to buffer the V
T EMP
pin, while the other half regulates the output current to satisfy
the current summation at its noninverting input:
I
OUT
+
V
TEMP
×
R
6
+
R
7
R
2
×
R
10
(
)
±
V
SET
R
2
+
R
6
+
R
7
R
2
×
R
10
T he change in output current with temperature is the derivative
of the transfer function:
I
OUT
T
=
V
TEMP
T
(
R
6
+
R
7)
R
2
×
R
10
SPAN TRIM
8
4
+8V TO +40V
V+
1/2 OP293
R4
20k
R9
100k
R2
1k
1/2 OP293
V
TEMP
2N1711
1
2
3
R1 10k
2
6
3
4
REF-43BZ
V
IN
V
OUT
V
TEMP
GND
R5
5k
R3
100k
6
5
ZERO
TRIM
V
SET
7
R6
3k
R7
5k
R8
1k
1N4002
R10
100
1%, 1/2 W
R
LOAD
I
OUT
ALL RESISTORS 1/4W, 5% UNLESS OTHERWISE NOTED
Figure 33. Temperature to 4–20 mA Transmitter
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| OP4930003SR | 制造商:Analog Devices 功能描述: |
| OP493EP | 制造商:Rochester Electronics LLC 功能描述:MICROPOWER RAIL/RAIL - Bulk |
| OP493ES | 制造商:AD 制造商全稱:Analog Devices 功能描述:Precision, Micropower Operational Amplifiers |
| OP493ES-REEL | 制造商:AD 制造商全稱:Analog Devices 功能描述:Precision, Micropower Operational Amplifiers |
| OP493FP | 制造商:Rochester Electronics LLC 功能描述:MICROPOWER RAIL/RAIL - Bulk 制造商:Analog Devices 功能描述: |
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