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參數(shù)資料
| 型號： | OP181GP |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | 運動控制電子 |
| 英文描述： | Ultralow Power, Rail-to-Rail Output Operational Amplifiers |
| 中文描述： | OP-AMP, 2500 uV OFFSET-MAX, 0.105 MHz BAND WIDTH, PDIP8 |
| 封裝： | PLASTIC, DIP-8 |
| 文件頁數(shù)： | 12/16頁 |
| 文件大?。?/td> | 448K |
| 代理商： | OP181GP |
OP181/OP281/OP481
–12–
REV. 0
A1
R1
R2
+3V
OP281-A
V
IN
2k
+3V
5.1k
+3V
+3V
V
OUT
Q1
5.1k
V
H
D1
10k
A2
R3
R4
+3V
V
L
D2
OP281-B
Figure 39. Using the OP281 as a Window Comparator
The threshold limits for the window are set by V
H
and V
L
,
provided that V
H
> V
L
. The output of A1 will stay at the
negative rail, in this case ground, as long as the input voltage is
less than V
H
. Similarly, the output of A2 will stay at ground as
long the input voltage is higher than V
L
. As long as V
IN
remains
between V
L
and V
H
, the outputs of both op amps will be 0 V.
With no current flowing in either D1 or D2, the base of Q1 will
stay at ground, putting the transistor in cutoff and forcing V
OUT
to the positive supply rail. If the input voltage rises above V
H
,
the output of A2 stays at ground, but the output of A1 will go to
the positive rail, and D1 will conduct current. This creates a
base voltage that will turn on Q1 and drive V
OUT
low. The same
condition occurs if V
IN
falls below V
L
with A2’s output going
high, and D2 conducting current. Therefore, V
OUT
will be high
if the input voltage is between V
L
and V
H
, and V
OUT
will be low
if the input voltage moves outside of that range.
The R1 and R2 voltage divider sets the upper window voltage,
and the R3 and R4 voltage divider sets the lower voltage for the
window. For the window comparator to function properly, V
H
must be a greater voltage than V
L
.
V
H
=
R
2
R
1
+
R
2
V
L
=
R
4
R
3
+
R
4
The 2 k
resistor connects the input voltage to the input termi-
nals to the op amps. This protects the OP281 from possible
excess current flowing into the input stages of the devices. D1
and D2 are small-signal switching diodes (1N4446 or equiva-
lent), and Q1 is a 2N2222 or equivalent NPN transistor.
A Low-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. Figure 40 shows an example
of a +5 V, single-supply current monitor that can be incorpo-
rated into the design of a voltage regulator with fold-back
current limiting or a high current power supply with crowbar
protection. The design capitalizes on the OP181’s common-
mode range that extends to ground. Current is monitored in the
power supply return path where a 0.1
shunt resistor, R
SENSE
,
creates a very small voltage drop. The voltage at the inverting
terminal becomes equal to the voltage at the noninverting
terminal through the feedback of Q1, which is a 2N2222 or
equivalent NPN transistor. This makes the voltage drop across
R1 equal to the voltage drop across R
SENSE
. Therefore, the
current through Q1 becomes directly proportional to the current
through R
SENSE
, and the output voltage is given by:
V
OUT
=
V
EE
R
2
R
1
×
R
SENSE
×
I
L
The voltage drop across R2 increases with I
L
increasing, so
V
OUT
decreases with higher supply current being sensed. For
the element values shown, the V
OUT
transfer characteristic is
–2.5 V/A, decreasing from V
EE
.
+5V
RETURN TO
GROUND
OP181
+5V
R2
2.49k
V
OUT
R1
100
0.1
R
SENSE
Q1
Figure 40. A Low-Side Load Current Monitor
Low Voltage Half-Wave and Full-Wave Rectifiers
Because of its quick overdrive recovery time, an OP281 can be
configured as a full-wave rectifier for low frequency (<500Hz)
applications. Figure 41 shows the schematic.
+3V
OP281-A
V
IN
= 2V p-p
2k
A1
+3V
OP281-B
A2
R1 = 100k
R2 = 100k
FULL-WAVE
RECTIFIED
OUTPUT
HALF-WAVE
RECTIFIED
OUTPUT
Figure 41. Single Supply Full- and Half-Wave Rectifiers
Using an OP281
10
0%
100
90
SCALE 0.1V/DIV
SCALE 0.1ms/DIV
Figure 42. Full-Wave Rectified Signal
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| OP181GS | Ultralow Power, Rail-to-Rail Output Operational Amplifiers |
| OP181 | Ultralow Power, Rail-to-Rail Output Operational Amplifiers |
| OP186 | 5 uA, Rail-to-Rail Output Operational Amplifier |
| OP186GRT | CONNECTOR ACCESSORY |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| OP181GS | 制造商:Rochester Electronics LLC 功能描述:SINGLE 5UA RAIL TO RAIL O - Bulk |
| OP181GS-REEL7 | 制造商:Rochester Electronics LLC 功能描述:- Tape and Reel |
| OP183 | 制造商:AD 制造商全稱:Analog Devices 功能描述:5 MHz Single-Supply Operational Amplifier |
| OP183_05 | 制造商:AD 制造商全稱:Analog Devices 功能描述:5 MHz Single-Supply Operational Amplifier |
| OP183GP | 制造商:Rochester Electronics LLC 功能描述:SINGLE SUPPLY 5MHZ OP AMP - Bulk 制造商:Analog Devices 功能描述: |
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