AMP04 查看數據表（PDF） - Analog Devices
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AMP04 Datasheet PDF : 17 Pages
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AMP04
4-20 mA Loop Receiver
At the receiving end of a 4-20 mA loop, the AMP04 makes a
convenient differential receiver to convert the current back to
a usable voltage (Figure 13). The 4-20 mA signal current passes
through a 100 Ω sense resistor. The voltage drop is differentially
amplified by the AMP04. The 4 mA offset is removed by the
offset correction circuit.
4–20mA
TRANSMITTER
+15V
1N4002
4–20mA
1k⍀
4–20mA
100⍀
1% 1k⍀
100k⍀
3
7
18
0.15F
AMP04 6
VOUT
2
5
0–1.6V FS
WIRE
RESISTANCE
4
–0.400V
POWER
SUPPLY
2
–15V
OP177
6
3
10k⍀
27k⍀
–15V
AD589
Figure 13. 4-to-20 mA Line Receiver
Low Power, Pulsed Load-Cell Amplifier
Figure 14 shows a 350 Ω load cell that is pulsed with a low duty
cycle to conserve power. The OP295’s rail-to-rail output capa-
bility allows a maximum voltage of 10 volts to be applied to the
bridge. The bridge voltage is selectively pulsed on when a mea-
surement is made. A negative-going pulse lasting 200 ms should
be applied to the MEASURE input. The long pulsewidth is
necessary to allow ample settling time for the long time constant
of the low-pass filter around the AMP04. A much faster settling
time can be achieved by omitting the filter capacitor.
12V
330⍀
1/2
OP295
1k⍀ 10k⍀
IN
OUT REF01
GND
2N3904
12V
50k⍀
1N4148
MEASURE
350⍀
7
3
1
8
2 AMP04 6
5
4
0.22F
VOUT
Single Supply Programmable Gain Instrumentation Amplifier
Combining with the single supply ADG221 quad analog switch,
the AMP04 makes a useful programmable gain amplifier that
can handle input and output signals at zero volts. Figure 15
shows the implementation. A logic low input to any of the gain
control ports will cause the gain to change by shorting a gain-
set resistor across AMP04’s Pins 1 and 8. Trimming is required
at higher gains to improve accuracy because the switch ON-
resistance becomes a more significant part of the gain-set
resistance. The gain of 500 setting has two switches connected
in parallel to reduce the switch resistance.
GAIN
CONTROL
5V TO 30V
13 ADG221 5
4
10F
0.1F 10
11
9
200⍀
7
6
GAIN OF 500
8
15
200⍀
14
GAIN OF 100
16
2
715⍀
3
GAIN OF 10
1
10.9k⍀
WR
INPUT
12
100k⍀
RG
1
RG
8
2
V+ 7
3
6
4
V–
REF
AMP04
5
0.22F
5V TO
30V
0.1F
VOUT
Figure 15. Single Supply Programmable Gain Instrumen-
tation Amplifier
The switch ON resistance is lower if the supply voltage is 12 volts
or higher. Additionally, the overall amplifier’s temperature coeffi-
cient also improves with higher supply voltage.
Figure 14. Pulsed Load Cell Bridge Amplifier
REV. C
–11–
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