AMP04FSZ-RL Analog Devices Inc, AMP04FSZ-RL Datasheet - Page 10

• Manufacturer Part Number: AMP04FSZ-RL
• Description: UNITY GAIN DIFF AM IC
• Manufacturer: Analog Devices Inc

Specifications of AMP04FSZ-RL

• Amplifier Type: Instrumentation
• Number Of Circuits: 1
• -3db Bandwidth: 700kHz
• Current - Input Bias: 22nA
• Voltage - Input Offset: 30µV
• Current - Supply: 750µA
• Current - Output / Channel: 30mA
• Voltage - Supply, Single/dual (±): 5 V ~ 30 V, ±2.5 V ~ 15 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Output Type: -
• Slew Rate: -
• Gain Bandwidth Product: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AMP04
APPLICATION CIRCUITS
Low Power Precision Single Supply RTD Amplifier
Figure 11 shows a linearized RTD amplifier that is powered
from a single 5 volt supply. However, the circuit will work up to
36 volts without modification. The RTD is excited by a 100 µA
constant current that is regulated by amplifier A (OP295). The
0.202 volts reference voltage used to generate the constant current
is divided down from the 2.500 volt reference. The AMP04 ampli-
fies the bridge output to a 10 mV/°C output coefficient.
The RTD is linearized by feeding a portion of the signal back to
the reference circuit, increasing the reference voltage as the
temperature increases. When calibrated properly, the RTD’s
nonlinearity error will be canceled.
To calibrate, either immerse the RTD into a zero-degree ice
bath or substitute an exact 100 Ω resistor in place of the RTD.
Then adjust bridge BALANCE potentiometer R3 for a 0 volt
R
26.7k
BALANCE
SENSE
1k
RTD
100
R1
3500
GAGE BRIDGE
R3
500
STRAIN
1.02k
R2
26.7k
R4
100
R5
50mV
FS
2
OP295
UNLESS OTHERWISE SPECIFIED, ALL RESISTORS
OR BETTER POTENTIOMETER < 50 PPM/ C
2.5V
1/2
REF43
OUT
3
GND
1
A
6
4
R6
11.5k
121k
0.202V
NOTES: ALL RESISTORS
R7
0.1 F
IN
C3
3
2
2
AMP04
7
ALL POTENTIOMETERS
5V
3
2
C2
0.1 F
7
4
OP295
8
4
5.00V
AMP04
5V
1/2
5V
383
1
U1
R8
7
4
5
2.49k
1
8
6
5
B
6
5
100
8
50
R10
R9
6
0.22 F
20mA
SPAN
0.5%,
C1
0.47 F
10-TURN
50k
FULL-SCALE
(0 C TO 400 C)
LINEARITY
0
5k
(@1/2 FS)
V
25 PPM/ C
25 PPM/ C
OUT
ADJ.
ADJ
4.00V
5082-2810
97.6k
1%
HP
4mA NULL
output. Note that a 0 volt output is also the negative output swing
limit of the AMP04 powered with a single supply. Therefore, be
sure to adjust R3 to first cause the output to swing positive and
then back off until the output just stops swinging negatively.
Next, set the LINEARITY ADJ potentiometer to the midrange.
Substitute an exact 247.04 Ω resistor (equivalent to 400°C
temperature) in place of the RTD. Adjust the FULL-SCALE
potentiometer for a 4.000 volts output.
Finally substitute a 175.84 Ω resistor (equivalent to 200°C
temperature), and adjust the LINEARITY ADJ potentiometer
for a 2.000 volts at the output. Repeat the full-scale and the
half-scale adjustments as needed.
When properly calibrated, the circuit achieves better than
± 0.5°C accuracy within a temperature measurement range
from 0°C to 400°C.
Precision 4-20 mA Loop Transmitter with Noninteractive Trim
Figure 12 shows a full bridge strain gage transducer amplifier
circuit that is powered off the 4-20 mA current loop. The AMP04
amplifies the bridge signal differentially and is converted to a
current by the output amplifier. The total quiescent current
drawn by the circuit, which includes the bridge, the amplifiers,
and the resistor biasing, is only a fraction of the 4 mA null
current that flows through the current-sense resistor R
The voltage across R
whose common-mode is fixed at the current summing reference
voltage, thus regulating the output current.
With no bridge signal, the 4 mA null is simply set up by the
50 kΩ NULL potentiometer plus the 976 kΩ resistors that
inject an offset that forces an 80 mV drop across R
50 mV full-scale bridge voltage, the AMP04 amplifies the
voltage-to-current converter for a full-scale of 20 mA at the
output. Since the OP90’s input operates at a constant 0 volt
common-mode voltage, the null and the span adjustments do
not interact with one another. Calibration is simple and easy
with the NULL adjusted first, followed by SPAN adjust. The
entire circuit can be remotely placed, and powered from the
4-20 mA 2-wire loop.
B
13.3k
15.8k
50k
976k
3
2
OP90
U2
7
4
220pF
100k
6
6
OUT
5%
REF02
GND
U3
R
4
2k
5%
SENSE
20
I
NULL
N
2
T1P29A
SENSE
+ I
SPAN
feeds back to the OP90’s input,
0.1 F
1N4002
4-20mA
12V TO 36V
SENSE
+V
R
100
LOAD
S
. At a
SENSE
.