Datasheet

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SBOS168D − DECEMBER 2000 − REVISED JANUARY 2006
www.ti.com
10
APPLICATIONS INFORMATION
The INA321 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 INA321 and INA2321. The power supply should be
capacitively decoupled with 0.1µF capacitors as close to
the INA321 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 INA321 family is fully specified over a supply range of
+2.7V to +5.5V, with key parameters assured over the
temperature range of −55°C to +125°C. Parameters that
vary significantly with operating conditions, such as load
conditions or temperature, are shown in the Typical
Characteristics.
The INA321 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.
160k
Ω
40k
Ω
40k
Ω
160k
Ω
3
2
5
1
78
4
Also drawn in simplified form:
6
REF
0.1
µ
F0.1
µ
F
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
100k
Ω
90k
Ω
190k
Ω
OPEN
100k
Ω
10k
Ω
10k
Ω
R
2
R
1
Shutdown
(For Single
Supply)
DESIRED GAIN
(V/V) R
1
R
2
G=5+5(R
2
/R
1
)
INA321
5
3
2
V
OUT
8
7
6
4
1
V+
Shutdown
RG
V
IN
−
V
−
V
IN
+
REF
Figure 1. Basic Connections
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.
INA321
5
3
2
V
OUT
8
7
6
4
1
V+
Shutdown
RG
V
IN
−
V−
V
IN
+
REF
(1)
Figure 2. Bridge Amplifier of the INA321