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參數(shù)資料
| 型號： | OP291 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | Micropower Single-Supply Rail-to-Rail Input/Output Op Amps |
| 中文描述： | 微功耗單電源軌到軌輸入/輸出運(yùn)算放大器 |
| 文件頁數(shù)： | 14/20頁 |
| 文件大?。?/td> | 479K |
| 代理商： | OP291 |
OP191/OP291/OP491
REV. 0
–14–
Single Supply RT D Amplifier
T he circuit in Figure 60 uses three op amps of the OP491 to
develop a bridge configuration for an RT D amplifier that
operates from a single +5 V supply. T he circuit takes advantage
of the OP491’s wide output swing range to generate a high
bridge excitation voltage of 3.9 V. In fact, because of the rail-
to-rail output swing, this circuit will work with supplies as low
as 4.0 V. Amplifier A1 servos the bridge to create a constant
excitation current in conjunction with the AD589, a 1.235 V
precision reference. T he op amp maintains the reference
voltage across the parallel combination of the 6.19 k
and 2.55
M
resistor, which generates a 200
μ
A current source. T his
current splits evenly and flows through both halves of the
bridge. T hus, 100
μ
A flows through the RT D to generate an
output voltage based on its resistance. A 3-wire RT D is used to
balance the line resistance in both 100
legs of the bridge to
improve accuracy.
1/4
OP491
V
OUT
365
365
1/4
OP491
100k
0.01pF
A3
+5V
GAIN = 274
100k
1/4
OP491
37.4k
+5V
AD589
2.55M
6.19k
200
10-TURNS
26.7k
26.7k
A2
A1
100
100
RTD
NOTE:
ALL RESISTORS 1% OR BETTER
Figure 60. Single Supply RTD Amplifier
Amplifiers A2 and A3 are configured in the two op amp IA
discussed above. T heir resistors are chosen to produce a gain of
274, such that each 1
°
C increase in temperature results in a
10 mV change in the output voltage, for ease of measurement.
A 0.01
μ
F capacitor is included in parallel with the 100 k
resistor on amplifier A3 to filter out any unwanted noise from
this high gain circuit. T his particular RC combination creates a
pole at 1.6 kHz.
APPLIC AT IONS
Single +3 V Supply, Instrumentation Amplifier
T he OP291’s low supply current and low voltage operation
make it ideal for battery powered applications such as the
instrumentation amplifier shown in Figure 59. T he circuit
utilizes the classic two op amp instrumentation amplifier
topology, with four resistors to set the gain. T he equation is
simply that of a noninverting amplifier as shown in the figure.
T he two resistors labeled R1 should be closely matched to each
other as well as both resistors labeled R2 to ensure good
common-mode rejection performance. Resistor networks
ensure the closest matching as well as matched drifts for good
temperature stability. Capacitor C1 is included to limit the
bandwidth and, therefore, the noise in sensitive applications.
T he value of this capacitor should be adjusted depending on the
desired closed-loop bandwidth of the instrumentation amplifier.
T he RC combination creates a pole at a frequency equal to
1/(2
π
×
R1C1). If AC-CMRR is critical, than a matched
capacitor to C1 should be included across the second resistor
labeled R1.
1/2
OP291
V
OUT
3
2
1
R1
R2
R2
1/2
OP291
5
6
7
R1
C1
100pF
V
IN
8
4
+3V
V
OUT
= (1 + R2
IN
Figure 59. Single +3 V Supply Instrumentation Amplifier
Because the OP291 accepts rail-to-rail inputs, the input
common-mode range includes both ground and the positive
supply of 3 V. Furthermore, the rail-to-rail output range
ensures the widest signal range possible and maximizes the
dynamic range of the system. Also, with its low supply current
of 300
μ
A/device, this circuit consumes a quiescent current of
only 600
μ
A, yet still exhibits a gain bandwidth of 3 MHz.
A question may arise about other instrumentation amplifier
topologies for single supply applications. For example, a
variation on this topology adds a fifth resistor between the two
inverting inputs of the op amps for gain setting. While that
topology works well in dual supply applications, it is inherently
not appropriate for single supply circuits. T he same could be
said for the traditional three op amp instrumentation amplifier.
In both cases, the circuits simply will not work in single supply
situations unless a false ground between the supplies is created.
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| OP291GS | Micropower Single-Supply Rail-to-Rail Input/Output Op Amps |
| OP191 | Micropower Single-Supply Rail-to-Rail Input/Output Op Amps |
| OP191GS | Micropower Single-Supply Rail-to-Rail Input/Output Op Amps |
| OP191GBC | Micropower Single-Supply Rail-to-Rail Input/Output Op Amps |
| OP291GBC | Micropower Single-Supply Rail-to-Rail Input/Output Op Amps |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| OP291A | 功能描述:紅外發(fā)射源 Infrared 890nm RoHS:否 制造商:Fairchild Semiconductor 波長:880 nm 射束角:+/- 25 輻射強(qiáng)度: 最大工作溫度:+ 100 C 最小工作溫度:- 40 C 封裝 / 箱體:Side Looker 封裝:Bulk |
| OP291A | 制造商:TT Electronics / OPTEK Technology 功能描述:Infrared LED |
| OP291B | 功能描述:紅外發(fā)射源 Infrared 890nm RoHS:否 制造商:Fairchild Semiconductor 波長:880 nm 射束角:+/- 25 輻射強(qiáng)度: 最大工作溫度:+ 100 C 最小工作溫度:- 40 C 封裝 / 箱體:Side Looker 封裝:Bulk |
| OP291C | 功能描述:紅外發(fā)射源 Infrared 890nm RoHS:否 制造商:Fairchild Semiconductor 波長:880 nm 射束角:+/- 25 輻射強(qiáng)度: 最大工作溫度:+ 100 C 最小工作溫度:- 40 C 封裝 / 箱體:Side Looker 封裝:Bulk |
| OP291GBC | 制造商:AD 制造商全稱:Analog Devices 功能描述:Micropower Single-Supply Rail-to-Rail Input/Output Op Amps |
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