®

INA103

11

12

7

5

16

15

13

14

6

2

1

INA103

V

OUT

R

F

11 10

R

F

G = 1+

2R

R

G

F

NOTE: AD625 equivalent pinout.

∆

R

FIGURE 7. Gain Adjustment of Output Stage.

FIGURE 8. Use of External Resistors for Gain Set.

OUTPUT STAGE

GAIN

(k

2

1k

2.4k

5

1.2k

632

Ω

10

1.2k

273

Ω

Output Stage Gain =

11

10

7

16

15

13

14

6

2

1

INA103

A common problem with many IC op amps and instrumentation amplifiers is shown in (a). Here, the amplifier’s input is driven beyond its linear common-mode

range, forcing the output of the amplifier into the supply rails. The output then “folds back”, i.e., a more positive input voltage now causes the output of the amplifier

to go negative. The INA103 has protection circuitry to prevent fold-back, and as shown in (b), limits cleanly.

(a) AD625 G = 1, V

IN

=

±15V, R

L

= 600

Ω

(b) INA103 G = 1, V

IN

=

±15V, R

L

= 600

Ω

FIGURE 9. INA103 Overload Condition Performance.

11

10

7

16

15

13

14

6

2

1

INA103

∆

V+

V–

MJ15012

100

MJ15011

(To headphone

or speaker)

Buffer inside feedback loop

Ω

11

10

7

16

15

13

14

6

2

1

INA103

20

Ω

CMR

Trim

10

Ω

Gain = 1V/V

(0dB)

Introduces

approximately

+0.2% Gain Error.

FIGURE 11. Increasing Output Circuit Drive.

FIGURE 10. Optional Circuit for Externally Trimming CMR.