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參數(shù)資料
| 型號(hào)： | OPA2379AIDG4 |
| 英文描述： | 1.8V, 2.9uA, 90kHz, Rail-to-Rail I/O OPERATIONAL AMPLIFIERS |
| 中文描述： | 1.8，2.9uA，90kHz，軌對(duì)軌輸入/輸出運(yùn)算放大器 |
| 文件頁(yè)數(shù)： | 9/12頁(yè) |
| 文件大?。?/td> | 238K |
| 代理商： | OPA2379AIDG4 |
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SBOS347A NOVEMBER 2005 REVISED DECEMBER 2005
www.ti.com
9
LOW-SIDE CURRENT MONITOR
The micropower OPA379 is well suited for current
monitoring circuits in applications such as a voltage
regulator with fold-back current limiting, or a high-current
power supply with crowbar protection. Figure 5 shows the
OPA379 monitoring the current in a power-supply return
path using a 0.1
shunt resistor. The NPN transistor, Q1
(2N2222 or equivalent) is used to generate equal voltages
at the inverting and noninverting inputs. Therefore, the
voltage drops across R
1
and R
S
are equal, and the current
flowing through Q1 is directly proportional to the current
flowing through R
S
. As the load current increases, the
current through Q1 increases, the voltage drop across R
2
increases, and this decreases the output voltage, V
OUT
, as
shown in Equation (5):
V
OUT
GND
R
2
R
1
R
S
I
L
0V
2.49k
100
0.1
I
L
2.49
I
L
R
S
0.1
5V
5V
R
1
100
R
2.49k
V
OUT
Return to Ground
I
L
Q1
OPA379
Figure 5. Low-Side Current Monitor
WINDOW COMPARATOR
Figure 6 shows the OPA2379 used as a window
comparator. The threshold limits are set by V
H
and V
L
, with
V
H
> V
L
. When V
IN
< V
H
, the output of A1 will be low. When
V
IN
>V
L
, the output of A2 will be low. Therefore, both op
amp outputs will be at 0V as long as V
IN
is between V
H
and
V
L
. This results in no current flowing through either diode,
Q1 in cutoff, with the base voltage at 0V, and V
OUT
forced
high.
If V
IN
falls below V
L
, the output of A2 will be high, current
will flow through D2, and V
OUT
will be low. Likewise, if V
IN
rises above V
H
, the output of A1 will be high, current will
flow through D1, and V
OUT
will be low.
The window comparator threshold voltages are set as
follows:
V
H
R
2
R
1
R
2
V
L
R
4
R
3
R
4
3V
A1
A2
D1
(2)
D2
(2)
10k
5.1k
5.1k
R
IN
2k
(1)
3V
3V
Q1
(3)
R
1
V
H
V
L
R
2
1/2
OPA2379
1/2
OPA2379
3V
V
OUT
V
IN
3V
R
3
R
4
NOTES: (1) R
protects A1 and A2 from possible excess current flow.
(2) IN4446 or equivalent diodes.
(3) 2N2222 or equivalent NPN transistor.
Figure 6. OPA2379 as a Window Comparator
(5)
(6)
(7)
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| OPA2379AIDR | 功能描述:運(yùn)算放大器 - 運(yùn)放 Dual 1.8V 2.9uA RR I/O Op Amp RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補(bǔ)償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| OPA2379AIDRG4 | 功能描述:運(yùn)算放大器 - 運(yùn)放 Dual 1.8V 2.9uA RR I/O Op Amp RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補(bǔ)償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| OPA237NA | 制造商:Texas Instruments 功能描述:OP AMP SINGLESUPPLY SMD SOT235 |
| OPA237NA/250 | 功能描述:運(yùn)算放大器 - 運(yùn)放 Sgl-Supply Op Amp MicroAmp Series RoHS:否 制造商:STMicroelectronics 通道數(shù)量:4 共模抑制比（最小值）:63 dB 輸入補(bǔ)償電壓:1 mV 輸入偏流（最大值）:10 pA 工作電源電壓:2.7 V to 5.5 V 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:QFN-16 轉(zhuǎn)換速度:0.89 V/us 關(guān)閉:No 輸出電流:55 mA 最大工作溫度:+ 125 C 封裝:Reel |
| OPA237NA/250 | 制造商:Texas Instruments 功能描述:IC SM OP-AMP SINGLE-SUPPLY |
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