Datasheet

INA159
SBOS333B − JULY 2005 − REVISED OCTOBER 2005
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7
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 0.1µF 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)
)
) 5
[(
V)
)
* V
REF
]
V
CM*
+
(
V*
)
* 5
[
V
REF
*
(
V*
)]
Where one REF pin is connected to the reference, and the
other pin grounded (1/2 reference connection):
V
CM)
+
(
V)
)
) 5
[(
V)
)
*
(
0.5V
REF
)]
V
CM*
+
(
V*
)
* 5
[(
0.5V
REF
)
*
(
V*
)]
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− V
REF
V
CM+
V
CM−
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− V
REF
V
CM+
V
CM−
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)