®

INA101

6

A

1

A

2

A

3

14

10k

Ω

10k

Ω

10k

Ω

10k

Ω

2

12

11

4

3

R

G

+15V

INA101

Common

V

20k

Ω

20k

Ω

–15V

13

DIP PACKAGE

A

A

10

5

OPA177

1k

Ω

1M

Ω

+15V

–15V

Approximately

±15mV Range

Pinout shown

is for DIP packages.

E

1

E

2

G = 1 +

40k

Ω

R

G

Input Offset Adjustment

Do not use to null source or system

offset (see text).

100k

Ω

+15V

Output Offset

Adjustment

1

V

COM

100k

Ω

67

OFFSET TRIMMING

The INA101 is laser trimmed for low offset voltage and

drift. Most applications require no external offset adjust-

ment. Figure 2 shows connection of an optional potentio-

meter connected to the Offset Adjust pins for trimming the

input offset voltage. (Pin numbers shown are for the DIP

package.) Use this adjustment to null the offset voltage in

high gain (G

≥ 100) with both inputs connected to ground.

Do not use this adjustment to null offset produced by the

source or other system offset since this will increase the

offset voltage drift by 0.3

µV/°C per 100µV of adjusted

offset.

Offset of the output amplifier usually dominates when the

INA101 is used in unity gain (G = 1). The output offset

voltage can be adjusted with the optional trim circuit con-

nected to the Common pin as shown in Figure 2. The voltage

applied to Common terminal is summed with the output.

Low impedance must be maintained at this node to assure

good common-mode rejection. The op amp connected as a

buffer provides low impedance.

THERMAL EFFECTS ON OFFSET VOLTAGE

To achieve lowest offset voltage and drift, prevent air

currents from circulating near the INA101. Rapid changes in

temperature will produce a thermocouple effect on the

package leads that will degrade offset voltage and drift. A

shield or cover that prevents air currents from flowing near

the INA101 will assure best performance.

FIGURE 2. Optional Trimming of Input and Output Offset Voltage.

A

1

A

2

A

3

8

7

10k

Ω

10k

Ω

10k

Ω

10k

Ω

2

9

5

4

1

10

R

G

No

Connection

+15V

INA101

Output

20k

Ω

20k

Ω

3

–15V

6

TO-100 PACKAGE

E

1

V

Tantalum

1µF

+

Tantalum

1µF

+

E

2

G = 1 +

40k

Ω

R

G

FIGURE 1. Basic Connections.