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®

INA154

APPLICATIONS INFORMATION

Figure 1 shows the basic connections required for operation

of the INA154. Decoupling capacitors are strongly recom-

mended in applications with noisy or high impedance power

supplies. The capacitors should be placed close to the

device pins as shown in Figure 1.

As shown in Figure 1, the output is referred to the reference

terminal (pin 1). A voltage applied to this pin will be

summed with output signal. The differential input signal is

connected to pins 2 and 3. The source impedances con-

nected to the pinouts must be nearly equal to assure good

common-mode rejection. A 5

Ω mismatch in source imped-

ance will degrade the common-mode rejection of a typical

device to approximately 80dB (a 10

Ω mismatch degrades

CMR to 74dB). If the source has a known impedance

mismatch, an additional resistor in series with the opposite

input can be used to preserve good common-mode rejection.

Do not interchange pins 1 and 3 or pins 2 and 5, even though

nominal resistor values are equal. The resistors are laser

trimmed for precise resistor ratios to achieve accurate gain

and highest CMR. Interchanging these pins would not

provide specified performance.

OPERATING VOLTAGE

The INA154 operates from

±4V to ±18V supplies with

excellent performance. Most behavior remains unchanged

throughout the full operating voltage range. Parameters

which vary significantly with operating voltage are shown

in the Typical Performance Curves.

INPUT VOLTAGE RANGE

The INA154 can accurately measure differential signals

that are beyond the positive or negative power supply rails.

The linear common-mode range extends from 2•(V+) – 5V

to 2•(V–) +5V. See the Typical Performance Curve, “Input

Common-Mode Range vs Output Voltage.”

OFFSET VOLTAGE TRIM

The INA154 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 1), 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 as

shown in Figure 2. The source impedance of a signal

applied to the Ref terminal should be less than 10

Ω to

maintain good common-mode rejection.

FIGURE 1. Basic Power Supply and Signal Connections.

V

3

5

6

3

V

O

INA154

V

O = V3 – V2

Offset Adjustment

Range =

±1V

2

R

3

R

1

R

2

R

4

V

2

10

Ω

150k

Ω

10

Ω

100k

Ω

+15V

–15V

1

FIGURE 2. Offset Adjustment.

V

3

5

6

3

INA154

V

OUT = V3 – V2

2

Ref

R

1

25k

Ω

R

3

25k

Ω

R

2

25k

Ω

R

4

V

2

25k

Ω

R

L

1

µF

V–

4

1

µF

V+

7

1