Datasheet

INA331, INA2331
SBOS215C
9
www.ti.com
APPLICATIONS INFORMATION
The INA331 is a modified version of the classic “two op amp”
instrumentation amplifier, with an additional gain amplifier.
Figure 1 shows the basic connections for the operation of the
INA331 and INA2331. The power supply should be capaci-
tively decoupled with 0.1µF capacitors as close to the INA331
as possible for noisy or high-impedance applications.
The output is referred to the reference terminal, which must
be at least 1.2V below the positive supply rail.
OPERATING VOLTAGE
The INA331 family is fully specified over a supply range of
+2.7V to +5.5V, with key parameters tested over the tempera-
ture range of –55°C to +125°C. Parameters that vary signifi-
cantly with operating conditions, such as load conditions or
temperature, are shown in the Typical Characteristics.
The INA331 may be operated on a single supply. Figure 2
shows a bridge amplifier circuit operated from a single +5V
supply. The bridge provides a small differential voltage riding
on an input common-mode voltage.
FIGURE 2. Single-Supply Bridge Amplifier.
FIGURE 1. Basic Connections.
40kΩ
10kΩ
10kΩ
40kΩ
3
2
5
1
78
4
Also drawn in simplified form:
6
REF
0.1µF
0.1µF
RG
V
IN
–
V
IN
+
V–
V+
A1
A3
A2
V
O
= ((V
IN
+) – (V
IN
–)) • G
Short V
OUT
to RG
for G = 5
5
10
50
100
SHORT
100kΩ
90kΩ
190kΩ
OPEN
100kΩ
10kΩ
10kΩ
R
2
R
1
Shutdown
(For Single
Supply)
DESIRED GAIN
(V/V) R
1
R
2
G = 5 + 5 (R
2
/ R
1
)
INA331
5
3
2
V
OUT
8
7
6
4
1
V+
Shutdown
RG
V
IN
–
V–
V
IN
+
REF
Bridge
Sensor
+5V
NOTE: (1) REF should be adjusted for the desired output level,
keeping in mind that the value of REF affects the common-mode
input range. See Typical Characteristics.
INA331
5
3
2
V
OUT
8
7
6
4
1
V+
Shutdown
RG
V
IN
–
V–
V
IN
+
REF
(1)