INA159

SBOS333B − JULY 2005 − REVISED OCTOBER 2005

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APPLICATION INFORMATION

The internal op amp of the INA159 has a rail-to-rail

common-mode voltage capability at its inputs. A rail-to-rail

op amp allows the use of

±10V inputs into a circuit biased

to 1/2 of a 5V reference (2.5V quiescent output). The inputs

to the op amp will swing from approximately 400mV to

3.75V in this application.

The unique input topology of the INA159 eliminates the

input offset transition region typical of most rail-to-rail

complementary stage operational amplifiers. This allows

the INA159 to provide superior glitch- and transition-free

performance over the entire common-mode range.

Good layout practice includes the use of a 0.1

µF bypass

capacitor placed closely across the supply pins.

COMMON-MODE RANGE

The common-mode range of the INA159 is a function of

supply voltage and reference. Where both pins, REF1 and

REF2, are connected together:

V

CM

V

CM

Where one REF pin is connected to the reference, and the

other pin grounded (1/2 reference connection):

V

CM

V

CM

Some typical values are shown in Table 1.

Table 1. Common-Mode Range For Various

Supply and Reference Voltages

REF 1 and REF 2 Connected Together

V+

V−

5

0

3

15

−15

5

0

2.5

17.5

−12.5

5

0

1.25

23.75

−6.25

1/2 Reference Connection

V+

V−

5

0

5

17.5

−12.5

5

0

4.096

19.76

−10.24

5

0

2.5

23.75

−6.25

3.3

0

3.3

11.55

−8.25

3.3

0

2.5

13.55

−6.25

3.3

0

1.25

16.675

−3.125

(1)

(2)

(3)

(4)