1
LT1168
Low Power, Single
Resistor Gain Programmable,
Precision Instrumentation Amplifier
The LT
1168 is a micropower, precision instrumentation am-
plifier that requires only one external resistor to set gains of
1 to 10,000. The low voltage noise of 10nV/
Hz (at 1kHz) is
not compromised by low power dissipation (350
A typical for
15V supplies). The wide supply range of
2.3V to
18V allows
the LT1168 to fit into a wide variety of industrial as well as
battery-powered applications.
The high accuracy of the LT1168 is due to a 20ppm maximum
nonlinearity and 0.4% max gain error (G = 10). Previous mono-
lithic instrumentation amps cannot handle a 2k load resistor
whereas the nonlinearity of the LT1168 is specified for loads
as low as 2k. The LT1168 is laser trimmed for very low input
offset voltage (40
V max), drift (0.3
V/
C), high CMRR (90dB,
G = 1) and PSRR (103dB, G = 1). Low input bias currents of
250pA max are achieved with the use of superbeta process-
ing. The output can handle capacitive loads up to 1000pF in
any gain configuration while the inputs are ESD protected up
to 13kV (human body). The LT1168 with two external 5k
resistors passes the IEC 1000-4-2 level 4 specification.
The LT1168 is a pin-for-pin improved second source for the
AD620 and INA118. The LT1168, offered in 8-pin PDIP and
SO packages, requires significantly less PC board area than
discrete op amp resistor designs. These advantages make
the LT1168 the most cost effective solution for precision
instrumentation amplifier applications.
s
Supply Current: 530
A Max
s
Meets IEC 1000-4-2 Level 4 (
15kV) ESD Tests
with Two External 5k Resistors
s
Single Gain Set Resistor: G = 1 to 10,000
s
Gain Error: G = 10, 0.4% Max
s
Input Offset Voltage Drift: 0.3
V/
C Max
s
Gain Nonlinearity: G = 10, 20ppm Max
s
Input Offset Voltage: 40
V Max
s
Input Bias Current: 250pA Max
s
PSRR at A
V
=1: 103dB Min
s
CMRR at A
V
= 1: 90dB Min
s
Wide Supply Range:
2.3V to
18V
s
1kHz Voltage Noise: 10nV/
Hz
s
0.1Hz to 10Hz Noise: 0.28
V
P-P
s
Available in 8-Pin PDIP and SO Packages
s
Bridge Amplifiers
s
Strain Gauge Amplifiers
s
Thermocouple Amplifiers
s
Differential to Single-Ended Converters
s
Differential Voltage to Current Converters
s
Data Acquisition
s
Battery-Powered and Portable Equipment
s
Medical Instrumentation
s
Scales
, LTC and LT are registered trademarks of Linear Technology Corporation.
Single Supply* Pressure Monitor
NONLINEARITY (100ppm/DIV)
G = 1000
OUTPUT VOLTAGE (2V/DIV)
1168 TA01a
R
L
= 2k
V
OUT
=
10V
Gain Nonlinearity
*See Theory of Operation section
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
+
2
3
2
1
1
1
1/2
LT1112
3.5k
5V
3.5k
3.5k
3.5k
8
7
6
1168 TA01
5
40k
20k
40k
DIGITAL
DATA
OUTPUT
4
R1
G = 200
249
3
REF
IN
AGND
ADC
LTC
1286
BI TECHNOLOGIES
67-8-3 R40KQ, (0.02% RATIO MATCH)
+
LT1168
2
LT1168
Supply Voltage ......................................................
20V
Differential Input Voltage (Within the
Supply Voltage) .....................................................
40V
Input Voltage (Equal to Supply Voltage) ................
20V
Input Current (Note 2) .......................................
20mA
Output Short-Circuit Duration (Note 3) ............ Indefinite
Operating Temperature Range (Note 4) .. 40
C to 85
C
Specified Temperature Range
LT1168AC/LT1168C (Note 5) ............. 40
C to 85
C
LT1168AI/LT1168I ............................. 40
C to 85
C
Storage Temperature Range ................. 40
C to 150
C
Lead Temperature (Soldering, 10 sec).................. 300
C
ORDER PART
NUMBER
S8 PART MARKING
LT1168ACN8
LT1168ACS8
LT1168AIN8
LT1168AIS8
LT1168CN8
LT1168CS8
LT1168IN8
LT1168IS8
1168A
1168AI
Consult factory for Military grade parts.
T
JMAX
= 150
C,
JA
= 150
C/ W (N8)
T
JMAX
= 150
C,
JA
= 190
C/ W (S8)
T
A
= 25
C. V
S
=
15V, V
CM
= 0V, R
L
= 10k unless otherwise noted.
1168
1168I
(Note 1)
LT1168AC/LT1168AI
LT1168C/LT1168I
SYMBOL
PARAMETER
CONDITIONS (Note 6)
MIN
TYP
MAX
MIN
TYP
MAX
UNITS
G
Gain Range
G = 1 + (49.4k/R
G
)
1
10k
1
10k
Gain Error
G = 1
0.008
0.02
0.015
0.03
%
G = 10 (Note 7)
0.04
0.4
0.05
0.5
%
G = 100 (Note 7)
0.04
0.5
0.05
0.6
%
G = 1000 (Note 7)
0.08
0.5
0.08
0.6
%
Gain Nonlinearity (Notes 7, 8)
V
O
=
10V, G = 1
2
6
3
10
ppm
V
O
=
10V,G = 10 and 100
10
20
15
25
ppm
V
O
=
10V, G = 1000
20
40
25
60
ppm
V
O
=
10V, G = 1, R
L
= 2k
4
15
5
20
ppm
V
O
=
10V,G = 10 and 100, R
L
= 2k
20
40
30
60
ppm
V
O
=
10V, G = 1000, R
L
= 2k
40
75
50
90
ppm
V
OST
Total Input Referred Offset Voltage V
OST
= V
OSI
+ V
OSO
/G
V
OSI
Input Offset Voltage
G = 1000, V
S
=
5V to
15V
15
40
20
60
V
V
OSO
Output Offset Voltage
G = 1, V
S
=
5V to
15V
40
200
50
300
V
I
OS
Input Offset Current
50
300
60
450
pA
I
B
Input Bias Current
40
250
80
500
pA
e
n
Input Noise Voltage, RTI
0.1Hz to 10Hz, G = 1
2.00
2.00
V
P-P
0.1Hz to 10Hz, G = 1000
0.28
0.28
V
P-P
Input Noise Voltage Density, RTI
f
O
= 1kHz
10
15
10
15
nV/
Hz
Output Noise Voltage Density, RTI f
O
= 1kHz (Note 9)
165
220
165
220
nV/
Hz
i
n
Input Noise Current
f
O
= 0.1Hz to 10Hz
5
5
pA
P-P
Input Noise Current Density
f
O
= 10Hz
74
74
fA/
Hz
R
IN
Input Resistance
V
IN
=
10V
300
1250
200
1250
G
ABSOLUTE AXI U RATI GS
W
W
W
U
PACKAGE/ORDER I FOR ATIO
U
U
W
1
2
3
4
8
7
6
5
TOP VIEW
R
G
IN
+IN
V
S
R
G
+V
S
OUTPUT
REF
N8 PACKAGE
8-LEAD PDIP
S8 PACKAGE
8-LEAD PLASTIC SO
+
ELECTRICAL CHARACTERISTICS
3
LT1168
LT1168AC
LT1168C
SYMBOL
PARAMETER
CONDITIONS (Note 6)
MIN
TYP
MAX
MIN
TYP
MAX
UNITS
Gain Error
G = 1
q
0.01
0.03
0.012
0.04
%
G = 10 (Note 7)
q
0.40
1.5
0.500
1.6
%
G = 100 (Note 7)
q
0.45
1.6
0.550
1.7
%
G = 1000 (Note 7)
q
0.50
1.7
0.600
1.8
%
Gain Nonlinearity
V
OUT
=
10V, G = 1
q
2
15
3
20
ppm
(Notes 7, 8)
V
OUT
=
10V, G = 10 and 100
q
7
30
10
35
ppm
V
OUT
=
10V, G = 1000
q
25
60
30
80
ppm
G/
T
Gain vs Temperature
G < 1000 (Note 7)
q
100
200
100
200
ppm/
C
LT1168AC/LT1168AI
LT1168C/LT1168I
SYMBOL
PARAMETER
CONDITIONS (Note 6)
MIN
TYP
MAX
MIN
TYP
MAX
UNITS
C
IN(DIFF)
Differential Input Capacitance
f
O
= 100kHz
1.6
1.6
pF
C
IN(CM)
Common Mode Input
f
O
= 100kHz
1.6
1.6
pF
Capacitance
V
CM
Input Voltage Range
G = 1, Other Input Grounded
V
S
=
2.3V to
5V
V
S
+ 1.9
+V
S
1.2
V
S
+ 1.9
+V
S
1.2
V
V
S
=
5V to
18V
V
S
+ 1.9
+V
S
1.4
V
S
+ 1.9
+V
S
1.4
V
CMRR
Common Mode
1k Source Imbalance,
Rejection Ratio
V
CM
= 0V to
10V
G = 1
90
95
85
95
dB
G = 10
106
115
100
115
dB
G = 100
120
135
110
135
dB
G = 1000
126
140
120
140
dB
PSRR
Power Supply
V
S
=
2.3V to
18V
Rejection Ratio
G = 1
103
108
100
108
dB
G = 10
122
128
118
128
dB
G = 100
131
145
126
145
dB
G = 1000
135
150
130
150
dB
I
S
Supply Current
V
S
=
2.3V to
18V
350
530
350
530
A
V
OUT
Output Voltage Swing
R
L
= 10k
V
S
=
2.3V to
5V
V
S
+ 1.1
+V
S
1.2
V
S
+ 1.1
+V
S
1.2
V
V
S
=
5V to
18V
V
S
+ 1.2
+V
S
1.3
V
S
+ 1.2
+V
S
1.3
V
I
OUT
Output Current
20
32
20
32
mA
BW
Bandwidth
G = 1
400
400
kHz
G = 10
200
200
kHz
G = 100
13
13
kHz
G = 1000
1
1
kHz
SR
Slew Rate
G = 1, V
OUT
=
10V
0.3
0.5
0.3
0.5
V/
s
Settling Time to 0.01%
10V Step
G = 1 to 100
30
30
s
G = 1000
200
200
s
REFIN
Reference Input Resistance
60
60
k
I
REFIN
Reference Input Current
V
REF
= 0V
18
18
A
V
REF
Reference Voltage Range
V
S
+ 1.6
+V
S
1.6
V
S
+ 1.6
+V
S
1.6
V
A
VREF
Reference Gain to Output
1
0.0001
1
0.0001
T
A
= 25
C. V
S
=
15V, V
CM
= 0V, R
L
= 10k unless otherwise noted.
The
q
denotes the specifications which apply over the 0
C
T
A
70
C temperature range. V
S
=
15V, V
CM
= 0V, R
L
= 10k unless
otherwise noted.
ELECTRICAL CHARACTERISTICS
4
LT1168
The
q
denotes the specifications which apply over the 0
C
T
A
70
C
temperature range. V
S
=
15V, V
CM
= 0V, R
L
= 10k unless otherwise noted.
The
q
denotes the specifications which apply over the 40
C
T
A
85
C temperature range. V
S
=
15V, V
CM
= 0V, R
L
= 10k unless
otherwise noted. (Note 8)
LT1168AI
LT1168I
SYMBOL
PARAMETER
CONDITIONS (Note 6)
MIN
TYP
MAX
MIN
TYP
MAX
UNITS
Gain Error
G = 1
q
0.014
0.04
0.015
0.05
%
G = 10 (Note 7)
q
0.600
1.9
0.700
2.0
%
G = 100 (Note 7)
q
0.600
2.0
0.700
2.1
%
G = 1000 (Note 7)
q
0.600
2.1
0.700
2.2
%
G
N
Gain Nonlinearity
V
O
=
10V, G = 1
q
3
20
5
25
ppm
(Notes 7, 8)
V
O
=
10V, G = 10 and 100
q
10
35
15
40
ppm
VO =
10V, G = 1000
q
30
70
35
100
ppm
G/
T
Gain vs Temperature
G < 1000 (Note 7)
q
100
200
100
200
ppm/
C
LT1168AC
LT1168C
SYMBOL
PARAMETER
CONDITIONS (Note 6)
MIN
TYP
MAX
MIN
TYP
MAX
UNITS
V
OST
Total Input Referred Offset Voltage
V
OST
= V
OSI
+ V
OSO
/G
V
OSI
Input Offset Voltage
V
S
=
5V to
15V
q
18
60
23
80
V
V
OSIH
Input Offset Voltage Hysteresis
(Notes 7, 10)
q
3.0
3.0
V
V
OSO
Output Offset Voltage
V
S
=
5V to
15V
q
60
380
70
500
V
V
OSOH
Output Offset Voltage Hysteresis (Notes 7, 10)
q
30
30
V
V
OSI
/T
Input Offset Drift (RTI)
(Note 9)
q
0.05
0.3
0.06
0.4
V/
C
V
OSO
/T
Output Offset Drift
(Note 9)
q
0.7
3
0.8
4
V/
C
I
OS
Input Offset Current
q
100
400
120
550
pA
I
OS
/T
Input Offset Current Drift
q
0.3
0.4
pA/
C
I
B
Input Bias Current
q
65
350
105
600
pA
I
B
/T
Input Bias Current Drift
q
1.4
1.4
pA/
C
V
CM
Input Voltage Range
G = 1, Other Input Grounded
V
S
=
2.3V to
5V
q
V
S
+ 2.1
+V
S
1.3 V
S
+ 2.1
+V
S
1.3
V
V
S
=
5V to
18V
q
V
S
+ 2.1
+V
S
1.4 V
S
+ 2.1
+V
S
1.4
V
CMRR
Common Mode
1k Source Imbalance,
Rejection Ratio
V
CM
= 0V to
10V
G = 1
q
88
92
83
92
dB
G = 10
q
100
110
97
110
dB
G = 100
q
115
120
113
120
dB
G = 1000
q
117
135
114
135
dB
PSRR
Power Supply
V
S
=
2.3V to
18V
Rejection Ratio
G = 1
q
102
115
98
115
dB
G = 10
q
123
130
118
130
dB
G = 100
q
127
135
124
135
dB
G = 1000
q
129
145
126
145
dB
I
S
Supply Current
V
S
=
2.3V to
18V
q
390
615
390
615
A
V
OUT
Output Voltage Swing
R
L
= 10k
V
S
=
2.3V to
5V
q
V
S
+ 1.4
+V
S
1.3 V
S
+ 1.4
+V
S
1.3
V
V
S
=
5V to
18V
q
V
S
+ 1.6
+V
S
1.5 V
S
+ 1.6
+V
S
1.5
V
I
OUT
Output Current
q
16
25
16
25
mA
SR
Slew Rate
G = 1, V
OUT
=
10V
q
0.25
0.48
0.25
0.48
V/
s
V
REF
Voltage Range
(Note 9)
q
V
S
+ 1.6
+V
S
1.6 V
S
+ 1.6
+V
S
1.6
V
ELECTRICAL CHARACTERISTICS
5
LT1168
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be imparied.
Note 2: If the input voltage exceeds the supplies, the input current should
be limited to less than 20mA.
Note 3: A heat sink may be required to keep the junction temperature
below absolute maximum.
Note 4: The LT1168AC/LT1168C are guaranteed functional over the
operating temperature range of 40
C and 85
C.
Note 5: The LT1168AC/LT1168C are guaranteed to meet specified
performance from 0
C to 70
C. The LT1168AC/LT1168C are designed,
characterized and expected to meet specified performance from 40
C to
85
C but are not tested or QA sampled at these temperatures. The
LT1168AI/LT1168I are guaranteed to meet specified performance from
40
C to 85
C.
Note 6: Typical parameters are defined as the 60% of the yield parameter
distribution.
Note 7: Does not include the tolerance of the external gain resistor R
G
.
Note 8: This parameter is measured in a high speed automatic tester that
does not measure the thermal effects with longer time constants. The
magnitude of these thermal effects are dependent on the package used,
heat sinking and air flow conditions.
Note 9: This parameter is not 100% tested.
Note 10: Hysteresis in offset voltage is created by package stress that
differs depending on whether the IC was previously at a higher or lower
temperature. Offset voltage hysteresis is always measured at 25
C, but
the IC is cycled to 85
C I-grade (or 70
C C-grade) or 40
C I-grade
(0
C C-grade) before successive measurement. 60% of the parts will
pass the typical limit on the data sheet.
The
q
denotes the specifications which apply over the 40
C
T
A
85
C
temperature range. V
S
=
15V, V
CM
= 0V, R
L
= 10k unless otherwise noted. (Note 5)
ELECTRICAL CHARACTERISTICS
LT1168AI
LT1168I
SYMBOL
PARAMETER
CONDITIONS (Note 6)
MIN
TYP
MAX
MIN
TYP
MAX
UNITS
V
OST
Total Input Referred Offset Voltage
V
OST
= V
OSI
+ V
OSO
/G
V
OSI
Input Offset Voltage
q
20
75
25
100
V
V
OSIH
Input Offset Voltage Hysteresis
(Notes 7, 10)
q
3.0
3.0
V
V
OSO
Output Offset Voltage
q
180
500
200
600
V
V
OSOH
Output Offset Voltage Hysteresis (Notes 7, 10)
q
30
30
V
V
OSI
/T
Input Offset Drift (RTI)
(Note 9)
q
0.05
0.3
0.06
0.4
V/
C
V
OSO
/T
Output Offset Drift
(Note 9)
q
0.8
5
1
6
V/
C
I
OS
Input Offset Current
q
110
550
120
700
pA
I
OS
/T
Input Offset Current Drift
q
0.3
0.3
pA/
C
I
B
Input Bias Current
q
120
500
220
800
pA
I
B
/T
Input Bias Current Drift
q
1.4
1.4
pA/
C
V
CM
Input Voltage Range
V
S
=
2.3V to
5V
q
V
S
+ 2.1
+V
S
1.3
V
S
+ 2.1
+V
S
1.3
V
V
S
=
5V to
18V
q
V
S
+ 2.1
+V
S
1.4
V
S
+ 2.1
+V
S
1.4
V
CMRR
Common Mode
1k Source Imbalance,
Rejection Ratio
V
CM
= 0V to
10V
G = 1
q
86
90
81
90
dB
G = 10
q
98
105
95
105
dB
G = 100
q
114
118
112
118
dB
G = 1000
q
116
133
112
133
dB
PSRR
Power Supply
V
S
=
2.3V to
18V
Rejection Ratio
G = 1
q
100
112
95
112
dB
G = 10
q
120
125
115
125
dB
G = 100
q
125
132
120
132
dB
G = 1000
q
128
140
125
140
dB
I
S
Supply Current
q
420
650
420
650
A
V
OUT
Output Voltage Swing
V
S
=
2.3V to
5V
q
V
S
+ 1.4
+V
S
1.3
V
S
+ 1.4
+V
S
1.3
V
V
S
=
5V to
18V
q
V
S
+ 1.6
+V
S
1.5
V
S
+ 1.6
+V
S
1.5
V
I
OUT
Output Current
q
15
22
15
22
mA
SR
Slew Rate
q
0.22
0.41
0.22
0.42
V/
s
V
REF
Voltage Range
(Note 9)
q
V
S
+ 1.6
+V
S
1.6
V
S
+ 1.6
+V
S
1.6
V
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