LT1991
Precision, 100µA
Gain Selectable Amplifier
FEATURES
DESCRIPTION
The LT®1991 combines a precision operational amplifier
with eight precision resistors to form a one-chip solution
for accurately amplifying voltages. Gains from –13 to 14
with a gain accuracy of 0.04% can be achieved using no
externalcomponents.Thedeviceisparticularlywellsuited
for use as a difference amplifier, where the excellent resis-
tor matching results in a common mode rejection ratio of
greater than 75dB.
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Pin Configurable as a Difference Amplifier,
Inverting and Noninverting Amplifier
Difference Amplifier
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Gain Range 1 to 13
CMRR >75dB
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Noninverting Amplifier
Gain Range 0.07 to 14
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Inverting Amplifier
Gain Range –0.08 to –13
The amplifier features a 50µV maximum input offset volt-
age and a gain bandwidth product of 560kHz. The device
operates from any supply voltage from 2.7V to 36V and
draws only 100µA supply current on a 5V supply. The
output swings to within 40mV of either supply rail.
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Gain Error <0.04%
Gain Drift < 3ppm/°C
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Wide Supply Range: Single 2.7V to Split 18V
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Micropower: 100µA Supply Current
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Precision: 50µV Maximum Input Offset Voltage
The resistors have excellent matching, 0.04% over tem-
peratureforthe450kresistors. Thematchingtemperature
coefficient is guaranteed less than 3ppm/°C. The resis-
tors are extremely linear with voltage, resulting in a gain
nonlinearity of less than 10ppm.
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560kHz Gain Bandwidth Product
Rail-to-Rail Output
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Space Saving 10-Lead MSOP and DFN Packages
APPLICATIONS
The LT1991 is fully specified at 5V and 15V supplies
and from –40°C to 125°C. The device is available in space
saving 10-lead MSOP and low profile (0.8mm) 3mm ×
3mm DFN packages.
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Handheld Instrumentation
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Medical Instrumentation
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Strain Gauge Amplifiers
Differential to Single-Ended Conversion
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L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
Rail-to-Rail Gain = 1 Difference Amplifier
Distribution of Resistor Matching
V
= V
+ ∆V
REF IN
OUT
5V
40
35
30
25
20
15
10
5
SWING 40mV TO
EITHER RAIL
450k RESISTORS
LT1991A
R
<0.1Ω
OUT
50k
150k
450k
450k
4pF
–
+
V
M(IN)
–
+
∆V
IN
450k
150k
50k
V
LT1991
P(IN)
450k
INPUT RANGE
–0.5V TO 5.1V
R
= 900kΩ
IN
0
4pF
0
–0.04
–0.02
0.02
0.04
RESISTOR MATCHING (%)
V
REF
= 2.5V
1991 TA01
1991 TA01b
1991fh
1