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參數(shù)資料
| 型號： | op191 |
| 廠商： | Analog Devices, Inc. |
| 英文描述： | Micropower Single-Supply Rail-to-Rail Input/Output Op Amps(微功耗單電源滿幅度運(yùn)算放大器) |
| 中文描述： | 微功耗單電源軌到軌輸入/輸出運(yùn)算放大器（微功耗單電源滿幅度運(yùn)算放大器） |
| 文件頁數(shù)： | 15/20頁 |
| 文件大?。?/td> | 487K |
| 代理商： | OP191 |
OP191/OP291/OP491
REV. 0
–15–
A +2.5 V Reference from a +3 V Supply
In many single-supply applications, the need for a 2.5 V
reference often arises. Many commercially available monolithic
2.5 V references require at least a minimum operating supply
voltage of 4 V. T he problem is exacerbated when the minimum
operating system supply voltage is + 3 V. T he circuit illustrated
in Figure 61 is an example of a +2.5 V that operates from a
single +3 V supply. T he circuit takes advantage of the OP291’s
rail-to-rail input and output voltage ranges to amplify an
AD589’s 1.235 V output to +2.5 V. T he OP291’s low T CV
OS
of 1
μ
V/
°
C helps to maintain an output voltage temperature
coefficient of less than 200 ppm/
°
C. T he circuit’s overall
temperature coefficient is dominated by R2 and R3’s tempera-
ture coefficient. Lower tempco resistors are recommended.
T he entire circuit draws less than 420
μ
A from a +3 V supply
at +25
°
C.
RESISTORS = 1%, 100ppm/
°
C
POTENTIOMETER = 10 TURN, 100ppm/
°
C
R3
100k
1/2
OP291
3
2
1
R2
100k
8
4
+3V
P1
5k
+2.5V
REF
R1
17.4k
AD589
Figure 61. A +2.5 V Reference that Operates on a Single
+3 V Supply
+5 V Only, 12-Bit DAC Swings Rail-to-Rail
T he OP191 family is ideal for use with a CMOS DAC to
generate a digitally controlled voltage with a wide output range.
Figure 62 shows the DAC8043 used in conjunction with the
AD589 to generate a voltage output from 0 V to 1.23 V T he
DAC is actually operated in “voltage switching” mode where
the reference is connected to the current output, I
OUT
, and the
output voltage is taken from the V
REF
pin. T his topology is
inherently noninverting as opposed to the classic current output
mode, which is inverting and, therefore, unsuitable for single
supply.
1/2
OP291
3
2
1
8
4
+5V
R1
17.8k
AD589
R2
R3
R4
232
1%
31%
11%
V
OUT
=4D
GND CLK SR1
4
7
6
5
DIGITAL
CONTROL
LD
V
REF
R
FB
V
DD
I
OUT
2
1
3
8
1.23V
+5V
DAC-8043
Figure 62. +5 V Only, 12-Bit DAC Swings Rail-to-Rail
T he OP291 serves two functions. First, it is required to buffer
the high output impedance of the DAC’s V
REF
pin, which is on
the order of 10 k
. T he op amp provides a low impedance
output to drive any following circuitry. Secondly, the op amp
amplifies the output signal to provide a rail-to-rail output swing.
In this particular case, the gain is set to 4.1 to generate a 5.0 V
output when the DAC is at full scale. If other output voltage
ranges are needed, such as 0 to 4.095, the gain can easily be
adjusted by altering the value of the resistors.
A High Side Current Monitor
In the design of power supply control circuits, a great deal of
design effort is focused on ensuring a pass transistor’s long-term
reliability over a wide range of load current conditions. As a
result, monitoring and limiting device power dissipation is of
prime importance in these designs. T he circuit illustrated in
Figure 63 is an example of a +5 V, single-supply high side
current monitor that can be incorporated into the design of a
voltage regulator with fold-back current limiting or a high
current power supply with crowbar protection. T his design uses
an OP291’s rail-to-rail input voltage range to sense the voltage
drop across a 0.1
current shunt. A p-channel MOSFET used
as the feedback element in the circuit converts the op amp’s
differential input voltage into a current. T his current is then
applied to R2 to generate a voltage that is a linear representation
of the load current. T he transfer equation for the current
monitor is given by:
Monitor Output = R2
×
R
SENSE
R
1
I
L
For the element values shown, the Monitor Output’s transfer
characteristic is 2.5 V/A.
1/2
OP291
3
2
1
8
4
+5V
R
0.1
+5V
+5V
I
L
S
G
M1
3N163
D
R2
2.49k
MONITOR
OUTPUT
R1
100
Figure 63. A High-Side Load Current Monitor
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| op491 | Micropower Single-Supply Rail-to-Rail Input/Output Op Amps(微功耗單電源滿幅度運(yùn)算放大器) |
| OP295GBC | DUAL/QUAD RAIL-TO-RAIL OPERATIONAL AMPLIFIERS |
| OP495GBC | DUAL/QUAD RAIL-TO-RAIL OPERATIONAL AMPLIFIERS |
| OP495 | DUAL/QUAD RAIL-TO-RAIL OPERATIONAL AMPLIFIERS |
| OP295 | DUAL/QUAD RAIL-TO-RAIL OPERATIONAL AMPLIFIERS |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| OP191_06 | 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 |
| OP1913-1 | 制造商: 功能描述: 制造商:undefined 功能描述: |
| OP191GBC | 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 |
| OP191GP | 制造商:Analog Devices 功能描述:IC OP AMP UPOWER RRI/O DIP8 191 制造商:Analog Devices 功能描述:Micropower Single-Supply Rail-to-Rail Input/Output Op Amps |
| OP191GS | 功能描述:IC OPAMP GP R-R 3MHZ 16MA 8SOIC RoHS:否 類別:集成電路 (IC) >> Linear - Amplifiers - Instrumentation 系列:- 標(biāo)準(zhǔn)包裝:2,500 系列:- 放大器類型:通用 電路數(shù):1 輸出類型:滿擺幅 轉(zhuǎn)換速率:0.11 V/µs 增益帶寬積:350kHz -3db帶寬:- 電流 - 輸入偏壓:4nA 電壓 - 輸入偏移:20µV 電流 - 電源:260µA 電流 - 輸出 / 通道:20mA 電壓 - 電源，單路/雙路(±):2.7 V ~ 36 V，±1.35 V ~ 18 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:8-SOIC（0.154"，3.90mm 寬） 供應(yīng)商設(shè)備封裝:8-SO 包裝:帶卷 (TR) |
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