OP413 Analog Devices, OP413 Datasheet - Page 14

• Manufacturer Part Number: OP413
• Description: Low Noise, Low Drift Single-Supply Operational Amplifier (Quad)
• Manufacturer: Analog Devices

Specifications of OP413

• -3db Bandwidth: 3.4MHz
• Slew Rate: 1.2V/µs
• Vos: 275µV
• Ib: 600nA
• # Opamps Per Pkg: 4
• Input Noise (nv/rthz): 4.7nV/rtHz
• Vcc-vee: 4V to 36V
• Isy Per Amplifier: 3mA
• Packages: SOIC

OP113/OP213/OP413
APPLICATION CIRCUITS
A HIGH PRECISION INDUSTRIAL LOAD-CELL
SCALE AMPLIFIER
The OPx13 family makes an excellent amplifier for
conditioning a load-cell bridge. Its low noise greatly improves
the signal resolution, allowing the load cell to operate with a
smaller output range, thus reducing its nonlinearity. Figure 41
shows one half of the OPx13 family used to generate a very
stable 10 V bridge excitation voltage while the second amplifier
provides a differential gain. R4 should be trimmed for
maximum common-mode rejection.
A LOW VOLTAGE, SINGLE SUPPLY STRAIN GAGE
AMPLIFIER
The true zero swing capability of the OPx13 family allows the
amplifier in Figure 42 to amplify the strain gage bridge
accurately even with no signal input while being powered by a
single 5 V supply. A stable 4 V bridge voltage is made possible
by the rail-to-rail OP295 amplifier, whose output can swing to
within a millivolt of either rail. This high voltage swing greatly
increases the bridge output signal without a corresponding
increase in bridge input.
350Ω
LOAD
CELL
2N2219A
1kΩ
Figure 41. Precision Load-Cell Scale Amplifier
R5
OP213
100mV
F.S.
1
+10V
1/2
8
A2
17.2kΩ
17.2kΩ
+
–
6
5
0.1%
0.1%
R1
R3
3
2
–
+
A1
–15V
4
+10V
500Ω
301Ω
0.1%
1/2
OP213
R4
R2
7
+15V
CMRR TRIM
10-TURN
T.C. LESS THAN 50ppm/°C
1
3
9
OUTPUT
0
FS
4
6
AD588BQ
10V
2
11 12
13
16
+ 10µF
7
–15V
14
15
10
8
Rev. F | Page 14 of 24
A HIGH ACCURACY LINEARIZED RTD
THERMOMETER AMPLIFIER
Zero suppressing the bridge facilitates simple linearization of
the resistor temperature device (RTD) by feeding back a small
amount of the output signal to the RTD. In Figure 43, the left
leg of the bridge is servoed to a virtual ground voltage by
Amplifier A1, and the right leg of the bridge is servoed to 0 V
by Amplifier A2. This eliminates any error resulting from
common-mode voltage change in the amplifier. A 3-wire RTD
is used to balance the wire resistance on both legs of the bridge,
thereby reducing temperature mismatch errors. The 5 V bridge
excitation is derived from the extremely stable AD588 reference
device with 1.5 ppm/°C drift performance.
Linearization of the RTD is done by feeding a fraction of the
output voltage back to the RTD in the form of a current. With
just the right amount of positive feedback, the amplifier output
will be linearly proportional to the temperature of the RTD.
35mV
350Ω
FS
2N2222A
4V
Figure 42. Single Supply Strain Gage Amplifier
R1
100kΩ
3
2
OP213
+
–
1/2
1
12kΩ
R8
OP295
2.1kΩ
R
5V
1/2
1
20kΩ
8
4
R5
G
R2
= 2127.4Ω
+
–
3
2
27.4Ω
R6
20kΩ
2.5V
R3
20kΩ
R7
6
OUT
GND
5
6
IN
4
2
OP295
+
–
REF43
1/2
5V
8
4
100kΩ
R4
7
OUTPUT
0V
3.5V