INA2126E Burr-Brown Corporation, INA2126E Datasheet - Page 7

• Manufacturer Part Number: INA2126E
• Description: MicroPOWER INSTRUMENTATION AMPLIFIER Single and Dual Versions
• Manufacturer: Burr-Brown Corporation

APPLICATION INFORMATION
Figure 1 shows the basic connections required for operation
of the INA126. Applications with noisy or high impedance
power supplies may require decoupling capacitors close to
the device pins as shown.
The output is referred to the output reference (Ref) terminal
which is normally grounded. This must be a low-impedance
connection to ensure good common-mode rejection. A resis-
tance of 8
device to degrade to approximately 80dB CMR.
Dual versions (INA2126) have feedback sense connections,
Sense
tive output terminals for proper operation. The sense con-
nection can be used to sense the output voltage directly at the
load for best accuracy.
SETTING THE GAIN
Gain is set by connecting an external resistor, R
Commonly used gains and R
Figure 1.
The 80k term in equation 1 comes from the internal metal film
resistors which are laser trimmed to accurate absolute values.
The accuracy and temperature coefficient of these resistors are
included in the gain accuracy and drift specifications.
The stability and temperature drift of the external gain
setting resistor, R
gain accuracy and drift can be directly inferred from the gain
FIGURE 1. Basic Connections.
A
and Sense
NC: No Connection.
DESIRED GAIN
10000
(V/V)
1000
2000
5000
in series with the Ref pin will cause a typical
100
200
500
10
20
50
5
B
G
G
. These must be connected to their respec-
, also affects gain. R
5333
1779
80.4
40.1
16.0
16k
842
410
162
( )
NC
R
8.0
Also drawn in simplified form:
G
R
k
G
G
V
V
resistor values are shown in
NEAREST 1%
IN
IN
+
–
R
R
G
15.8k
G
5360
1780
VALUE
80.6
40.2
15.8
7.87
845
412
162
NC
G
’s contribution to
INA126
G
Ref
, as shown:
(1)
external sense connection.
V
Pin numbers are
for single version
Dual version has
O
7
V
V
IN
IN
+
–
equation (1). Low resistor values required for high gain can
make wiring resistance important. Sockets add to the wiring
resistance, which will contribute additional gain error in
gains of approximately 100 or greater.
OFFSET TRIMMING
The INA126 and INA2126 are laser trimmed for low offset
voltage and offset voltage drift. Most applications require no
external offset adjustment. Figure 2 shows an optional cir-
cuit for trimming the output offset voltage. The voltage
applied to the Ref terminal is added to the output signal. An
op amp buffer is used to provide low impedance at the Ref
terminal to preserve good common-mode rejection.
FIGURE 2. Optional Trimming of Output Offset Voltage.
V
V
external sense connection.
R
IN
IN
–
+
G
Dual version has
R
3
8
1
2
G
Adjustment Range
INA126
±10mV
10k
A
A
INA126
Ref
1
2
INA126, INA2126
V+
V–
4
7
40k
10k
0.1µF
0.1µF
40k
OPA237
V
O
6
5
Ref
10k
Load
V+
V–
G = 5 +
V
O
= (V
100
100
1/2 REF200
1/2 REF200
V
O
IN
100µA
100µA
+
80k
+
–
R
– V
G
IN
–
) G
®