INA2128PA Burr-Brown Corporation, INA2128PA Datasheet - Page 8

• Manufacturer Part Number: INA2128PA
• Description: Dual/ Low Power INSTRUMENTATION AMPLIFIER
• Manufacturer: Burr-Brown Corporation

APPLICATION INFORMATION
Figure 1 shows the basic connections required for operation
of the INA2128. 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) terminals
(Ref
be low-impedance connections to assure good common-
mode rejection. A resistance of 8
will cause a typical device to degrade to approximately
80dB CMR (G = 1).
The INA2128 has a separate output sense feedback connec-
tions Sense
respective output terminals for proper operation. The output
sense connection can be used to sense the output voltage
directly at the load for best accuracy.
SETTING THE GAIN
Gain of the INA2128 is set by connecting a single external
resistor, R
Commonly used gains and resistor values are shown in
Figure 1.
The 50k term in equation 1 comes from the sum of the two
FIGURE 1. Basic Connections.
DESIRED
A
10000
GAIN
1000
2000
5000
100
200
500
and Ref
10
20
50
1
2
5
G
A
, connected as shown:
NC: No Connection.
®
and Sense
B
50.00k
12.50k
5.556k
2.632k
505.1
251.3
100.2
50.05
25.01
10.00
5.001
1.02k
) which are normally grounded. These must
INA2128
( )
NC
R
G
G 1
B
NEAREST 1% R
. These must be connected to their
49.9k
12.4k
5.62k
2.61k
1.02k
49.9
24.9
4.99
511
249
100
( )
NC
10
50k
R
G
in series with a Ref pin
G
Pin numbers for
Channel B shown
in parenthesis.
V
V
IN
IN
–
+
V
V
IN
IN
–
+
R
G
(16)
(14)
(13)
(15)
Also drawn in simplified form:
1
3
4
2
R
G
Over-Voltage
Over-Voltage
Protection
Protection
(1)
INA2128
8
Ref
internal feedback resistors of A
metal film resistors are laser trimmed to accurate absolute
values. The accuracy and temperature coefficient of these
resistors are included in the gain accuracy and drift specifi-
cations of the INA2128.
The stability and temperature drift of the external gain
setting resistor, R
gain accuracy and drift can be directly inferred from the gain
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.
DYNAMIC PERFORMANCE
The typical performance curve “Gain vs Frequency” shows
that despite its low quiescent current, the INA2128 achieves
wide bandwidth, even at high gain. This is due to its current-
feedback topology. Settling time also remains excellent at
high gain—see “Settling Time vs Gain.”
NOISE PERFORMANCE
The INA2128 provides very low noise in most applications.
Low frequency noise is approximately 0.2 Vp-p measured
from 0.1 to 10Hz (G
improved noise when compared to state-of-the-art chopper-
stabilized amplifiers.
A
A
1
2
25k
25k
V
O
9
8
40k
40k
V+
V–
NOTE: If channel is unused,
connect inputs to ground, sense
to V
INA2128
0.1µF
0.1µF
G
, also affects gain. R
O
, and leave Ref open-circuit.
A
40k
40k
100). This provides dramatically
3
Ref
1
and A
7
(10)
6
(11)
5
(12)
Sense
G
’s contribution to
2
Load
V
. These on-chip
G = 1 +
O
= G • (V
V
+
–
O
50k
IN
+
R
G
– V
IN
–
)