7

®

INA2132

APPLICATIONS INFORMATION

Figure 1 shows the basic connections required for operation

of the INA2132. Power supply bypass capacitors should be

connected close to the device pins.

The differential input signal is connected to pins 2 and 3 (or

pins 6 and 5) as shown. The source impedances connected to

the inputs must be nearly equal to assure good common-

mode rejection. An 8

Ω mismatch in source impedance will

degrade the common-mode rejection of a typical device to

approximately 80dB. Gain accuracy will also be slightly

affected. If the source has a known impedance mismatch, an

additional resistor in series with one input can be used to

preserve good common-mode rejection.

Do not interchange pins 3 and 14 (or pins 5 and 8) or pins

2 and 12 (or pins 6 and 10), even though nominal resistor

values are equal. These resistors are laser-trimmed for pre-

cise resistor ratios to achieve accurate gain and highest

CMRR. Interchanging these pins may not provide specified

performance. As shown in Figure 1, sense line should be

connected as close to the load as possible.

For more information, see the typical performance curve titled

“Input Common-Mode Voltage Range vs Output Voltage.”

OPERATING VOLTAGE

The INA2132 operates from single (+2.7V to +36V) or dual

(

±1.35V to ±18V) supplies with excellent performance.

Specifications are production tested with +5V and

±15V

supplies. Most behavior remains unchanged throughout the

full operating voltage range. Parameters which vary signifi-

cantly with operating voltage are shown in the Typical

Performance Curves.

The INA2132 can accurately measure differential signals

that are beyond the power supply rails. Linear common-

mode range extends to twice the negative power supply

voltage and nearly twice the positive power supply voltage.

Output phase reversal does not occur when the inputs to the

internal operational amplifier are overloaded to either rail.

See typical performance curve, “Common-Mode Range vs

Output Voltage.”

OFFSET VOLTAGE TRIM

The INA2132 is laser-trimmed for low offset voltage and

drift. Most applications require no external offset adjust-

ment. Figure 2 shows an optional circuit for trimming the

output offset voltage. The output is referred to the output

reference terminal (pin 14 or pin 8), which is normally

grounded. A voltage applied to the Ref terminal will be

summed with the output signal. This can be used to null

offset voltage. The source impedance of a signal applied to

the Ref terminal should be less than 8

Ω to maintain good

common-mode rejection. To assure low impedance at the

Ref terminal, the trim voltage can be buffered with an op

amp, such as the OPA277.

FIGURE 1. Basic Power Supply and Signal Connections.

FIGURE 2. Offset Adjustment.

To ensure valid operation of the differential amplifier, please

note the following points:

example, with

±15V supplies and a 100kΩ load, the

output will be defined by:

3) Input common-mode range at the nodes of the op amp

must be V–

≤ V

to the differential amp (+In and –In) meet this criteria,

limit the common-mode voltage inputs to:

V

3

12 (10)

13 (9)

3 (5)

V

O

INA2132

V

Offset Adjustment

Range =

±500µV

2 (6)

R

3

Ref

R

1

R

2

R

4

V

2

8

Ω

R = 237k

Ω

8

Ω

100k

Ω

+15V

–15V

14 (8)

NOTE: For

±750µV range, R = 158kΩ.

V

3

12 (10)

13 (9)

3 (5)

INA2132

V

2(6)

R

3

Ref

R

1

R

2

R

4

V

2

40k

Ω

40k

Ω

40k

Ω

40k

Ω

R

L

1

µF

NOTE: Pin numbers in parentheses ( ) refer to channel B.

V–

4

1

µF

V+

11

14 (8)