LTC6910-X [Linear]
Precision, 100μA Gain Selectable Amplifier; 精密， 100μA增益可选放大器器
| 型号： | LTC6910-X |
| 厂家： | 
Linear |
| 描述： | Precision, 100μA Gain Selectable Amplifier |
| 文件： | 总28页 (文件大小：758K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
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.
n
Pin Configurable as a Difference Amplifier,
Inverting and Noninverting Amplifier
Difference Amplifier
n
Gain Range 1 to 13
CMRR >75dB
n
Noninverting Amplifier
Gain Range 0.07 to 14
n
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.
n
Gain Error <0.04%
Gain Drift < 3ppm/°C
n
n
Wide Supply Range: Single 2.7V to Split 18V
n
Micropower: 100µA Supply Current
n
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.
n
560kHz Gain Bandwidth Product
Rail-to-Rail Output
n
n
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.
n
Handheld Instrumentation
n
Medical Instrumentation
n
Strain Gauge Amplifiers
Differential to Single-Ended Conversion
n
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
LT1991
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Specified Temperature Range (Note 5)
+
–
Total Supply Voltage (V to V ) ................................40V
Input Voltage (Pins P1/M1, Note 2) ........................ 60V
Input Voltage
LT1991C...............................................–40°C to 85°C
LT1991I................................................–40°C to 85°C
LT1991H............................................. –40°C to 125°C
Maximum Junction Temperature
+
–
(Other Inputs Note 2) ..................V + 0.2V to V – 0.2V
Output Short-Circuit Duration (Note 3) ........... Indefinite
Operating Temperature Range (Note 4)
DD Package ......................................................... 125°C
MS Package ......................................................... 150°C
Storage Temperature Range
DD Package ........................................... –65°C to 125°C
MS Package........................................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec) ..................300°C
LT1991C...............................................–40°C to 85°C
LT1991I................................................–40°C to 85°C
LT1991H............................................. –40°C to 125°C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
P1
P3
P9
1
2
3
4
5
10 M1
P1
P3
P9
EE
REF
1
2
3
4
5
10 M1
9
8
7
6
M3
M9
9
8
7
6
M3
M9
CC
OUT
V
EE
V
V
V
CC
REF
OUT
MS PACKAGE
10-LEAD PLASTIC MSOP
DD PACKAGE
10-LEAD (3mm × 3mm) PLASTIC DFN
T
= 150°C, q = 230°C/W
JA
JMAX
EXPOSED PAD CONNECTED TO V PCB
EE
CONNECTION OPTIONAL
T
JMAX
= 125°C, q = 43°C/W
JA
ORDER INFORMATION
LEAD FREE FINISH
LT1991CDD#PBF
LT1991ACDD#PBF
LT1991IDD#PBF
LT1991AIDD#PBF
LT1991HDD#PBF
LT1991CMS#PBF
LT1991ACMS#PBF
LT1991IMS#PBF
LT1991AIMS#PBF
LT1991HMS#PBF
TAPE AND REEL
PART MARKING* PACKAGE DESCRIPTION
SPECIFIED TEMPERATURE RANGE
0°C to 70°C
LTCT1991CDD#TRPBF
LT1991ACDD#TRPBF
LT1991IDD#TRPBF
LT1991AIDD#TRPBF
LT1991HDD#TRPBF
LT1991CMS#TRPBF
LT1991ACMS#TRPBF
LT1991IMS#TRPBF
LT1991AIMS#TRPBF
LT1991HMS#TRPBF
LBMM
LBMM
LBMM
LBMM
LBMM
LTQD
10-Lead (3mm × 3mm) Plastic DFN
10-Lead (3mm × 3mm) Plastic DFN
10-Lead (3mm × 3mm) Plastic DFN
10-Lead (3mm × 3mm) Plastic DFN
10-Lead (3mm × 3mm) Plastic DFN
10-Lead Plastic MSOP
0°C to 70°C
–40°C to 85°C
–40°C to 85°C
–40°C to 125°C
0°C to 70°C
LTQD
10-Lead Plastic MSOP
0°C to 70°C
LTQD
10-Lead Plastic MSOP
–40°C to 85°C
–40°C to 85°C
–40°C to 125°C
LTQD
10-Lead Plastic MSOP
LTQD
10-Lead Plastic MSOP
Consult LTC Marketing for parts specified with wider operating temperature ranges. *Temperature grades are identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
1991fh
2
LT1991
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the operating
temperature range of 0°C to 70°C for C-grade parts and –40°C to 85°C for I-grade parts, otherwise specifications are at TA = 25°C.
Difference amplifier configuration, VS = 5V, 0V or 15V; VCM = VREF = half supply, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
V = 15V, V
MIN
TYP
MAX
UNITS
∆G
Gain Error
= 10V; R = 10k
OUT L
S
l
l
l
l
G = 1; LT1991A
G = 1; LT1991
0.04
0.08
0.06
0.12
%
%
%
%
G = 3 or 9; LT1991A
G = 3 or 9; LT1991
l
l
GNL
Gain Nonlinearity
V = 15V; V
=
=
10V; R = 10k
1
10
3
ppm
S
OUT
L
∆G/∆T
CMRR
Gain Drift vs Temperature (Note 6)
V = 15V; V
10V; R = 10k
0.3
ppm/°C
S
OUT
L
Common Mode Rejection Ratio,
Referred to Inputs (RTI)
V = 15V; V
=
15.2V
S
CM
l
l
l
l
G = 9; LT1991A
G = 3; LT1991A
G = 1; LT1991A
80
75
75
60
100
93
90
70
dB
dB
dB
dB
Any Gain; LT1991
V
Input Voltage Range (Note 7)
P1/M1 Inputs
CM
l
l
l
V = 15V; V = 0V
–28
–0.5
0.75
27.6
5.1
2.35
V
V
V
S
REF
V = 5V, 0V; V = 2.5V
S
REF
REF
V = 3V, 0V; V = 1.25V
S
P1/M1 Inputs, P9/M9 Connected to REF
V = 15V; V = 0V
l
l
l
–60
–14
–1.5
60
16.8
7.3
V
V
V
S
REF
V = 5V, 0V; V = 2.5V
S
REF
V = 3V, 0V; V = 1.25V
S
REF
P3/M3 Inputs
l
l
l
V = 15V; V = 0V
–15.2
0.5
0.95
15.2
4.2
1.95
V
V
V
S
REF
V = 5V, 0V; V = 2.5V
S
REF
REF
V = 3V, 0V; V = 1.25V
S
P9/M9 Inputs
l
l
l
V = 15V; V = 0V
–15.2
0.85
1.0
15.2
3.9
1.9
V
V
V
S
REF
V = 5V, 0V; V = 2.5V
S
REF
REF
V = 3V, 0V; V = 1.25V
S
V
Op Amp Offset Voltage (Note 8)
LT1991AMS, V = 5V, 0V
15
15
25
25
50
µV
µV
OS
S
l
l
l
135
LT1991AMS, V = 15V
80
160
µV
µV
S
LT1991MS
LT1991DD
100
200
µV
µV
150
250
µV
µV
l
l
∆V /∆T
Op Amp Offset Voltage Drift (Note 6)
Op Amp Input Bias Current (Note 11)
0.3
2.5
1
µV/°C
OS
IB
5
7.5
nA
nA
l
l
l
I
OS
Op Amp Input Offset Current (Note 11) LT1991A
LT1991
50
50
500
750
pA
pA
1000
1500
pA
pA
Op Amp Input Noise Voltage
0.01Hz to 1Hz
0.35
0.07
0.25
0.05
µV
P-P
RMS
0.01Hz to 1Hz
0.1Hz to 10Hz
0.1Hz to 10Hz
µV
µV
RMS
P-P
µV
e
n
Input Noise Voltage Density
G = 1; f = 1kHz
G = 9; f = 1kHz
180
46
nV/√Hz
nV/√Hz
1991fh
3
LT1991
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the operating
temperature range of 0°C to 70°C for C-grade parts and –40°C to 85°C for I-grade parts, otherwise specifications are at TA = 25°C.
Difference amplifier configuration, VS = 5V, 0V or 15V; VCM = VREF = half supply, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
l
l
l
R
IN
Input Impedance (Note 10)
P1 (M1 = Ground)
P3 (M3 = Ground)
P9 (M9 = Ground)
630
420
350
900
600
500
1170
780
650
kΩ
kΩ
kΩ
l
l
l
M1 (P1 = Ground)
M3 (P3 = Ground)
M9 (P9 = Ground)
315
105
35
450
150
50
585
195
65
kΩ
kΩ
kΩ
l
l
l
l
∆R
Resistor Matching (Note 9)
450k Resistors, LT1991A
Other Resistors, LT1991A
450k Resistors, LT1991
Other Resistors, LT1991
0.01
0.02
0.02
0.04
0.04
0.06
0.08
0.12
%
%
%
%
l
l
∆R/∆T
PSRR
Resistor Temperature Coefficient (Note 6) Resistor Matching
Absolute Value
0.3
3
ppm/°C
ppm/°C
–30
l
l
Power Supply Rejection Ratio
Minimum Supply Voltage
V = 1.35V to 18V (Note 8)
S
105
135
2.4
dB
V
2.7
V
OUT
Output Voltage Swing (to Either Rail)
No Load
S
V = 5V, 0V
40
55
65
110
mV
mV
mV
l
l
V = 5V, 0V
S
V = 15V
S
1mA Load
V = 5V, 0V
150
225
275
300
mV
mV
mV
S
l
l
V = 5V, 0V
S
V = 15V
S
I
SC
Output Short-Circuit Current (Sourcing) Drive Output Positive;
Short Output to Ground
8
4
12
21
mA
mA
l
l
Output Short-Circuit Current (Sinking)
Drive Output Negative;
Short Output to V or Midsupply
8
4
mA
mA
S
BW
–3dB Bandwidth
G = 1
G = 3
G = 9
110
78
40
kHz
kHz
kHz
GBWP
Op Amp Gain Bandwidth Product
Rise Time, Fall Time
f = 10kHz
560
kHz
t , t
G = 1; 0.1V Step; 10% to 90%
G = 9; 0.1V Step; 10% to 90%
3
8
µs
µs
r
f
t
Settling Time to 0.01%
G = 1; V = 5V, 0V; 2V Step
42
48
114
74
µs
µs
µs
µs
s
S
G = 1; V = 5V, 0V; –2V Step
S
G = 1; V = 15V, 10V Step
S
G = 1; V = 15V, –10V Step
S
l
l
SR
Slew Rate
V = 5V, 0V; V
= 1V to 4V
0.06
0.08
0.12
0.12
V/µs
V/µs
S
OUT
V = 15V; V
=
10V; V
= 5V
S
OUT
MEAS
I
Supply Current
V = 5V, 0V
100
110
150
µA
µA
s
S
l
l
V = 15V
S
130
160
210
µA
µA
1991fh
4
LT1991
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the operating
temperature range of –40°C to 125°C for H-grade parts, otherwise specifications are at TA = 25°C. Difference amplifier configuration,
VS = 5V, 0V or 15V; VCM = VREF = half supply, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
∆G
Gain Error
V = 15V, V
=
10V; R = 10k
L
S
OUT
l
l
G = 1
0.08
0.12
%
%
G = 3 or 9
l
l
GNL
Gain Nonlinearity
V = 15V; V
=
=
10V; R = 10k
1
10
3
ppm
S
OUT
L
∆G/∆T
CMRR
Gain Drift vs Temperature (Note 6)
V = 15V; V
10V; R = 10k
0.3
ppm/°C
S
OUT
L
Common Mode Rejection Ratio,
Referred to Inputs (RTI)
V = 15V; V
=
15.2V
S
CM
l
l
l
G = 9
G = 3
G = 1
77
70
70
100
93
90
dB
dB
dB
V
Input Voltage Range (Note 7)
P1/M1 Inputs
V = 15V; V = 0V
CM
l
l
l
–28
–0.5
0.75
27.6
5.1
2.35
V
V
V
S
REF
V = 5V, 0V; V = 2.5V
S
REF
V = 3V, 0V; V = 1.25V
S
REF
P1/M1 Inputs, P9/M9 Connected to REF
V = 15V; V = 0V
l
l
l
–60
–14
–1.5
60
16.8
7.3
V
V
V
S
REF
V = 5V, 0V; V = 2.5V
S
REF
V = 3V, 0V; V = 1.25V
S
REF
P3/M3 Inputs
l
l
l
V = 15V; V = 0V
–15.2
0.5
0.95
15.2
4.2
1.95
V
V
V
S
REF
V = 5V, 0V; V = 2.5V
S
REF
REF
V = 3V, 0V; V = 1.25V
S
P9/M9 Inputs
l
l
l
V = 15V; V = 0V
–15.2
0.85
1.0
15.2
3.9
1.9
V
V
V
S
REF
V = 5V, 0V; V = 2.5V
S
REF
REF
V = 3V, 0V; V = 1.25V
S
V
Op Amp Offset Voltage (Note 8)
LT1991MS
25
25
100
285
µV
µV
OS
l
LT1991DD
150
295
µV
µV
l
l
∆V /∆T
Op Amp Offset Voltage Drift (Note 6)
Op Amp Input Bias Current (Note 11)
0.3
2.5
1
µV/°C
OS
IB
5
25
nA
nA
l
l
I
OS
Op Amp Input Offset Current (Note 11)
Op Amp Input Noise Voltage
50
1000
4500
pA
pA
0.01Hz to 1Hz
0.01Hz to 1Hz
0.1Hz to 10Hz
0.1Hz to 10Hz
0.35
0.07
0.25
0.05
µV
P-P
RMS
P-P
RMS
µV
µV
µV
e
Input Noise Voltage Density
Input Impedance (Note 10)
G = 1; f = 1kHz
G = 9; f = 1kHz
180
46
nV/√Hz
nV/√Hz
n
l
l
l
R
P1 (M1 = Ground)
P3 (M3 = Ground)
P9 (M9 = Ground)
630
420
350
900
600
500
1170
780
650
kΩ
kΩ
kΩ
IN
l
l
l
M1 (P1 = Ground)
M3 (P3 = Ground)
M9 (P9 = Ground)
315
105
35
450
150
50
585
195
65
kΩ
kΩ
kΩ
l
l
∆R
Resistor Matching (Note 9)
450k Resistors
Other Resistors
0.02
0.04
0.08
0.12
%
%
l
l
∆R/∆T
Resistor Temperature Coefficient (Note 6) Resistor Matching
Absolute Value
0.3
–30
3
ppm/°C
ppm/°C
1991fh
5
LT1991
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the operating
temperature range of –40°C to 125°C for H-grade parts, otherwise specifications are at TA = 25°C. Difference amplifier configuration,
VS = 5V, 0V or 15V; VCM = VREF = half supply, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
135
2.4
MAX
UNITS
dB
l
l
PSRR
Power Supply Rejection Ratio
Minimum Supply Voltage
Output Voltage Swing (to Either Rail)
V = 1.35V to 18V (Note 8)
S
105
2.7
V
V
OUT
No Load
V = 5V, 0V
40
55
75
120
mV
mV
mV
S
l
l
V = 5V, 0V
S
V = 15V
S
1mA Load
V = 5V, 0V
150
225
300
340
mV
mV
mV
S
l
l
V = 5V, 0V
S
V = 15V
S
I
Output Short-Circuit Current (Sourcing) Drive Output Positive;
Short Output to Ground
8
4
12
21
mA
mA
SC
l
l
Output Short-Circuit Current (Sinking)
Drive Output Negative;
Short Output to V or Midsupply
8
4
mA
mA
S
BW
–3dB Bandwidth
G = 1
G = 3
G = 9
110
78
40
kHz
kHz
kHz
GBWP
Op Amp Gain Bandwidth Product
Rise Time, Fall Time
f = 10kHz
560
kHz
t , t
G = 1; 0.1V Step; 10% to 90%
G = 9; 0.1V Step; 10% to 90%
3
8
µs
µs
r
f
t
Settling Time to 0.01%
G = 1; V = 5V, 0V; 2V Step
42
48
114
74
µs
µs
µs
µs
s
S
G = 1; V = 5V, 0V; –2V Step
S
G = 1; V = 15V, 10V Step
S
G = 1; V = 15V, –10V Step
S
l
l
SR
Slew Rate
V = 5V, 0V; V
= 1V to 4V
0.06
0.08
0.12
0.12
V/µs
V/µs
S
OUT
V = 15V; V
=
10V; V
= 5V
S
OUT
MEAS
I
Supply Current
V = 5V, 0V
100
110
180
µA
µA
s
S
l
l
V = 15V
S
130
160
250
µA
µA
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 6: This parameter is not 100% tested.
Note 7: Input voltage range is guaranteed by the CMRR test at V = 15V.
S
For the other voltages, this parameter is guaranteed by design and through
correlation with the 15V test. See the Applications Information section to
determine the valid input voltage range under various operating conditions.
Note 2: The P3/M3 and P9/M9 inputs should not be taken more than 0.2V
beyond the supply rails. The P1/M1 inputs can withstand 60V if P9/M9
Note 8: Offset voltage, offset voltage drift and PSRR are defined as
are grounded and V = 15V (see Applications Information section about
S
referred to the internal op amp. You can calculate output offset as follows.
“High Voltage CM Difference Amplifiers”).
In the case of balanced source resistance, V
= V • NOISEGAIN
OS
OS,OUT
Note 3: A heat sink may be required to keep the junction temperature
below absolute maximum ratings.
+ I • 450k + I • 450k • (1– R /R ) where R and R are the total
OS B P N P N
resistance at the op amp positive and negative terminal respectively.
Note 4: Both the LT1991C and LT1991I are guaranteed functional over the
–40°C to 85°C temperature range. The LTC1991H is guaranteed functional
over the –40°C to 125°C temperature range.
Note 9: Applies to resistors that are connected to the inverting inputs.
Resistor matching is not tested directly, but is guaranteed by the gain
error test.
Note 5: The LT1991C is guaranteed to meet the specified performance
from 0°C to 70°C and is designed, characterized and expected to meet
specified performance from –40°C to 85°C but is not tested or QA sampled
at these temperatures. The LT1991I is guaranteed to meet specified
performance from –40°C to 85°C. The LT1991H is guaranteed to meet
specified performance from –40°C to 125°C.
Note 10: Input impedance is tested by a combination of direct
measurements and correlation to the CMRR and gain error tests.
Note 11: I and I are tested at V = 5V, 0V only.
B
OS
S
1991fh
6
LT1991
TYPICAL PERFORMANCE CHARACTERISTICS
(Difference Amplifier Configuration)
Output Voltage Swing
Output Voltage Swing
Supply Current vs Supply Voltage
vs Temperature
vs Load Current (Output Low)
V
200
175
150
125
100
75
CC
1400
1200
1000
800
V
= 5V, 0V
V
= 5V, 0V
S
S
NO LOAD
–20
–40
–60
OUTPUT HIGH
(RIGHT AXIS)
T
= 85°C
T
= 85°C
A
A
T
= 25°C
A
T
= –40°C
A
T
= 25°C
A
600
60
40
20
T
= –40°C
A
400
50
OUTPUT LOW
(LEFT AXIS)
200
25
V
EE
V
EE
0
–25
0
25
50
75
125
5
6
7
8
9
10
–50
100
0
0
2
4
6
8
10 12 14 16 18 20
1
2
3
4
LOAD CURRENT (mA)
TEMPERATURE (°C)
SUPPLY VOLTAGE ( Vꢀ
1991 G02
1991 G03
1991 G01
Output Voltage Swing
vs Load Current (Output High)
Output Short-Circuit Current
vs Temperature
Input Offset Voltage
vs Difference Gain
25
20
15
10
5
150
100
50
V
CC
V = 5V, 0V
S
V
= 5V, 0V
V
S
= 5V, 0V
S
REPRESENTATIVE PARTS
–100
–200
–300
–400
–500
–600
–700
–800
–900
–1000
SINKING
T
= –40°C
A
T
= 85°C
T
A
= 25°C
A
0
SOURCING
–50
–100
–150
0
–50
4
0
1
2
3
5
6
7
8
9
10
1
2
3
4
5
6
7
8
9
10 11 12 13
0
25
50
75 100 125
–25
LOAD CURRENT (mA)
TEMPERATURE (°C)
GAIN (V/V)
1991 G06
1991 G04
1991 G05
Output Offset Voltage
vs Difference Gain
Gain Error vs Load Current
Slew Rate vs Temperature
0.30
0.25
0.20
0.15
0.10
0.05
0
1000
750
0.04
0.03
0.02
0.01
0
V
= 5V, 0V
GAIN = 1
GAIN = 1
S
REPRESENTATIVE PARTS
V
V
A
=
OUT
15V
10V
= 25°C
V
V
=
OUT
15V
= 10V
S
S
=
T
500
250
–
SR (FALLING EDGE)
0
+
SR (RISING EDGE)
–250
–500
–750
–1000
–0.01
–0.02
–0.03
–0.04
REPRESENTATIVE UNITS
50
TEMPERATURE (°C)
100 125
1991 G09
1
2
4
–50 –25
0
25
75
0
5
1
2
3
4
5
6
7
8
9
10 11 12 13
3
GAIN (V/V)
LOAD CURRENT (mA)
1991 G07
1991 G08
1991fh
7
LT1991
TYPICAL PERFORMANCE CHARACTERISTICS
(Difference Amplifier Configuration)
Bandwidth vs Gain
CMRR vs Frequency
PSRR vs Frequency
120
110
100
90
80
70
60
50
40
30
20
10
0
120
120
100
80
60
40
20
0
V
T
= 5V, 0V
V
T
= 5V, 0V
= 25°C
S
A
V
T
= 5V, 0V
= 25°C
S
A
S
A
110
100
90
80
70
60
50
40
30
20
10
0
GAIN = 9
GAIN = 1
= 25°C
GAIN = 3
GAIN = 9
GAIN = 1
GAIN = 3
10
100
1k
10k
100k
1M
10
100
1k
FREQUENCY (Hz)
10k
100k
1
2
3
4
5
6
7
8
9
10 11 12 13
FREQUENCY (Hz)
GAIN SETTING (V/V)
1991 G11
1991 G12
1991 G10
Output Impedance vs Frequency
CMRR vs Temperature
Gain Error vs Temperature
0.030
0.025
0.020
0.015
0.010
0.005
0
1000
100
10
120
100
80
60
40
20
0
V
T
= 5V, 0V
= 25°C
GAIN = 1
GAIN = 1
S
A
V
= 15V
V
= 15V
S
S
GAIN = 9
GAIN = 3
GAIN = 1
1
0.1
0.01
REPRESENTATIVE UNITS
REPRESENTATIVE UNITS
50
TEMPERATURE (°C)
100 125
–50 –25
0
25
75
50
TEMPERATURE (°C)
100 125
–50 –25
0
25
75
1
10
100
1k
10k
100k
FREQUENCY (Hz)
1991 G13
1991 G15
1991 G14
Gain vs Frequency
Gain and Phase vs Frequency
0.01Hz to 1Hz Voltage Noise
30
20
2
1
V
A
= 5V, 0V
= 25°C
S
V
= 5V, 0V
= 25°C
S
V
= ±±1V
= 21°C
S
A
PHASE
GAIN
T
0
T
A
T
GAIN = 9
GAIN = 3
GAIN = 1
MEASURED IN G =±3
REFERRED TO OP AMP INPUTS
0
–45
–90
–135
–180
–1
–2
–3
–4
–5
–6
–7
–8
10
GAIN = 1
0
–10
–20
1
10
100
600
0.5
1
10
100
400
0
±0 20 30 40 10 60 70 80 90 ±00
FREQUENCY (kHz)
FREQUENCY (kHz)
TIME (s)
1991 G16
1991 G17
±99± G2±
1991fh
8
LT1991
TYPICAL PERFORMANCE CHARACTERISTICS
Small Signal Transient Response
Small Signal Transient Response
Small Signal Transient Response
GAIN = 3
GAIN = 9
GAIN = 1
50mV/DIV
50mV/DIV
50mV/DIV
1991 G19
1991 G20
1991 G18
5µs/DIV
5µs/DIV
5µs/DIV
PIN FUNCTIONS
P1(Pin1):NoninvertingGain-of-1input. Connectsa450k
internal resistor to the op amp’s noninverting input.
(Difference Amplifier Configuration)
OUT (Pin 6): Output. V
= V + 1 • (V – V ) + 3 •
OUT REF P1 M1
(V – V ) + 9 • (V – V ).
P3 M3 P9 M9
P3(Pin2):NoninvertingGain-of-3input. Connectsa150k
internal resistor to the op amp’s noninverting input.
V
(Pin 7): Positive Power Supply. Can be anything from
CC
2.7V to 36V above the V voltage.
EE
P9 (Pin 3): Noninverting Gain-of-9 input. Connects a 50k
internal resistor to the op amp’s noninverting input.
M9 (Pin 8): Inverting Gain-of-9 input. Connects a 50k
internal resistor to the op amp’s inverting input.
V (Pin 4): Negative Power Supply. Can be either ground
M3 (Pin 9): Inverting Gain-of-3 input. Connects a 150k
EE
(in single supply applications), or a negative voltage (in
internal resistor to the op amp’s inverting input.
split supply applications).
M1 (Pin 10): Inverting Gain-of-1 input. Connects a 450k
internal resistor to the op amp’s inverting input.
REF (Pin 5): Reference Input. Sets the output level when
differencebetweeninputsiszero.Connectsa450kinternal
resistor to the op amp’s noninverting input.
Exposed Pad: Must be soldered to PCB.
BLOCK DIAGRAM
M1 M3 M9
V
OUT
6
CC
10
9
8
7
50k
450k
4pF
150k
450k
450k
INM
INP
OUT
LT1991
150k
450k
50k
4pF
1
2
3
4
5
1991 BD
P1
P3
P9
V
REF
EE
1991fh
9
LT1991
APPLICATIONS INFORMATION
Introduction
admittances. Because it has 9 times the admittance, the
voltage applied to the P9 input has 9 times the effect of
the voltage applied to the P1 input.
TheLT1991maybethelastopampyoueverhavetostock.
Because it provides you with several precision matched
resistors, you can easily configure it into several different
classicalgaincircuitswithoutaddingexternalcomponents.
The several pages of simple circuits in this data sheet
demonstrate just how easy the LT1991 is to use. It can
be configured into difference amplifiers, as well as into
inverting and noninverting single ended amplifiers. The
fact that the resistors and op amp are provided together
in such a small package will often save you board space
and reduce complexity for easy probing.
Bandwidth
The bandwidth of the LT1991 will depend on the gain you
select (or more accurately the noise gain resulting from
the gain you select). In the lowest configurable gain of 1,
the –3dB bandwidth is limited to 450kHz, with peaking of
about 2dB at 280kHz. In the highest configurable gains,
bandwidth is limited to 32kHz.
Input Noise
The Op Amp
The LT1991 input noise is dominated by the Johnson
noise of the internal resistors (√4kTR). Paralleling all
four resistors to the +input gives a 32.1kΩ resistance,
for 23nV/√Hz of voltage noise. The equivalent network
on the –input gives another 23nV/√Hz , and taking their
RMSsumgivesatotal33nV/√Hzinputreferrednoisefloor.
Output noise depends on configuration and noise gain.
The op amp internal to the LT1991 is a precision device
with15µVtypicaloffsetvoltageand3nAinputbiascurrent.
The input offset current is extremely low, so matching the
source resistance seen by the op amp inputs will provide
for the best output accuracy. The op amp inputs are not
rail-to-rail, but extend to within 1.2V of V and 1V of
CC
V . For many configurations though, the chip inputs will
EE
Input Resistance
function rail-to-rail because of effective attenuation to the
+input. The output is truly rail-to-rail, getting to within
40mV of the supply rails. The gain bandwidth product of
the op amp is about 560kHz. In noise gains of 2 or more,
itisstableintocapacitiveloadsupto500pF. Innoisegains
below 2, it is stable into capacitive loads up to 100pF.
The LT1991 input resistances vary with configuration,
but once configured are apparent on inspection. Note that
resistors connected to the op amp’s –input are looking
intoavirtualground, sotheysimplyparallel. Anyfeedback
resistancearound the opamp does not contribute to input
resistance. Resistors connected to the op amp’s +input
are looking into a high impedance, so they add as paral-
lel or series depending on how they are connected, and
whether or not some of them are grounded. The op amp
+input itself presents a very high GΩ impedance. In the
classical noninverting op amp configuration, the LT1991
presents the high input impedance of the op amp, as is
usual for the noninverting case.
The Resistors
The resistors internal to the LT1991 are very well matched
SiChrome based elements protected with barrier metal.
Although their absolute tolerance is fairly poor ( 30%),
their matching is to within 0.04%. This allows the chip to
achieve a CMRR of 75dB, and gain errors within 0.04%.
The resistor values are 50k, 150k, and 2 of 450k, con-
nected to each of the inputs. The resistors have power
limitations of 1watt for the 450k resistors, 0.3watt for the
150k resistors and 0.5watt for the 50k resistors; however,
in practice, power dissipation will be limited well below
these values by the maximum voltage allowed on the
input and REF pins. The 450k resistors connected to the
M1 and P1 inputs are isolated from the substrate, and can
thereforebetakenbeyondthesupplyvoltages.Thenaming
of the pins “P1,” “P3,” “P9,” etc., is based on their relative
Common Mode Input Voltage Range
The LT1991 valid common mode input range is limited
by three factors:
1. Maximum allowed voltage on the pins
2. The input voltage range of the internal op amp
3. Valid output voltage
1991fh
10
LT1991
APPLICATIONS INFORMATION
The maximum voltage allowed on the P3, M3, P9, and as a gain of 13 difference amplifier on a single supply
M9 inputs includes the positive and negative supply plus with the output REF connected to ground. This is a great
a diode drop. These pins should not be driven more than circuit, but it does not support V = 0V at any common
DM
0.2V outside of the supply rails. This is because they are mode because the output clips into ground while trying
connected through diodes to internal manufacturing post- to produce 0V . It can be fixed simply by declaring the
OUT
package trim circuitry, and through a substrate diode to valid input differential range not to extend below +4mV,
V . If more than 10mA is allowed to flow through these or by elevating the REF pin above 40mV, or by providing
EE
pins, there is a risk that the LT1991 will be detrimmed or a negative supply.
damaged. The P1 and M1 inputs do not have clamp diodes
Calculating Input Voltage Range
or substrate diodes or trim circuitry and can be taken well
outside the supply rails. The maximum allowed voltage on
the P1 and M1 pins is 60V.
Figure 2 shows the LT1991 in the generalized case of
a difference amplifier, with the inputs shorted for the
common mode calculation. The values of R and R are
dictated by how the P inputs and REF pin are connected.
By superposition we can write:
The input voltage range of the internal op amp extends
F
G
to within 1.2V of V and 1V of V . The voltage at which
CC
EE
the op amp inputs common mode is determined by the
voltage at the op amp’s +input, and this is determined by
the voltages on pins P1, P3, P9 and REF (see “Calculating
Input Voltage Range” section). This is true provided that
the op amp is functioning and feedback is maintaining the
inputs at the same voltage, which brings us to the third
requirement.
V
= V • (R /(R + R )) + V • (R /(R + R ))
INT
EXT
F
F
G
REF
G
F
G
Or, solving for V
:
EXT
V
EXT
= V • (1 + R /R ) – V • R /R
INT G F REF G
F
But valid V voltages are limited to V – 1.2V and V
INT
CC
EE
+ 1V, so:
For valid circuit function, the op amp output must not be
clipped.Theoutputwillclipiftheinputsignalsareattempt-
ing to force it to within 40mV of its supply voltages. This and:
usually happens due to too large a signal level, but it can
also occur with zero input differential and must therefore
be included as an example of a common mode problem.
Consider Figure 1. This shows the LT1991 configured
MAX V = (V – 1.2) • (1 + R /R ) – V • R /R
EXT
CC
G
F
REF
G
F
MIN V = (V + 1) • (1 + R /R ) – V • R /R
F
EXT
EE
G
F
REF
G
R
F
5V
V
CC
R
R
G
7
–
+
50k
450k
8
V
EXT
V
INT
4pF
150k
450k
9
G
V
EE
V
REF
10
R
F
1991 F02
–
+
–
6
5
V
DM
0V
V
= 13 • V
DM
OUT
Figure 2. Calculating CM Input Voltage Range
450k
150k
50k
+
1
2
3
V
CM
2.5V
4pF
These two voltages represent the high and low extremes
of the common mode input range, if the other limits have
not already been exceeded (1 and 3, above). In most
cases, the inverting inputs M1 through M9 can be taken
further than these two extremes because doing this does
not move the op amp input common mode. To calculate
450k
REF
LT1991
1991 F01
4
Figure 1. Difference Amplifier Cannot Produce
0V on a Single Supply. Provide a Negative
Supply, or Raise Pin 5, or Provide 4mV of VDM
the limit on this additional range, see Figure 3. Note that,
1991fh
11
LT1991
APPLICATIONS INFORMATION
with V
= 0, the op amp output is at V . From the
representation of the circuit on the top. The LT1991 is
shown on the bottom configured in a precision gain
of 5.5. One of the benefits of the noninverting op amp
configuration is that the input impedance is extremely
high. The LT1991 maintains this benefit. Given the finite
number of available feedback resistors in the LT1991, the
number of gain configurations is also finite. The complete
list of such Hi-Z input noninverting gain configurations is
shown in Table 1. Many of these are also represented in
Figure 5 in schematic form. Note that the P-side resistor
inputs have been connected so as to match the source
impedance seen by the internal op amp inputs. Note also
thatgainandnoisegainareidentical,foroptimalprecision.
MORE
REF
max V (the high cm limit), as V
goes positive, the
EXT
MORE
op amp output will go more negative from V
amount V
by the
REF
• R /R , so:
MORE
F
G
V
= V – V
• R /R
MORE F G
OUT
REF
Or:
V
= (V – V ) • R /R
REF OUT G F
MORE
The most negative that V
can go is V + 0.04V, so:
EE
OUT
Max V
= (V – V – 0.04V) • R /R
REF EE G F
MORE
(should be positive)
The situation where this function is negative, and there-
fore problematic, when V = 0 and V = 0, has already
REF
EE
R
F
been dealt with in Figure 1. The strength of the equation
is demonstrated in that it provides the three solutions
R
G
suggested in Figure 1: raise V , lower V , or provide
REF
EE
–
+
some negative V
.
MORE
V
OUT
V
IN
Likewise, from the lower common mode extreme, mak-
ing the negative input more negative will raise the output
V
= GAIN • V
OUT
IN
G
GAIN = 1 + R /R
F
CLASSICAL NONINVERTING OP AMP CONFIGURATION.
YOU PROVIDE THE RESISTORS.
voltage, limited by V – 0.04V.
CC
MIN V
= (V – V + 0.04V) • R /R
MORE
REF
CC
G
F
(should be negative)
R
F
50k
450k
4pF
8
V
150k
450k
CC
9
R
R
G
G
V
–
+
MORE
10
–
+
V
INT
V
6
EXT
V
OUT
MAX OR MIN
450k
150k
50k
1
2
3
V
EE
V
REF
4pF
R
1991 F03
F
Figure 3. Calculating Additional
Voltage Range of Inverting Inputs
450k
LT1991
5
V
IN
Again, the additional input range calculated here is only
available provided the other remaining constraint is not
violated, the maximum voltage allowed on the pin.
CLASSICAL NONINVERTING OP AMP CONFIGURATION
IMPLEMENTED WITH LT1991. R = 225k, R = 50k, GAIN = 5.5.
F
G
GAIN IS ACHIEVED BY GROUNDING, FLOATING OR FEEDING BACK
THE AVAILABLE RESISTORS TO ARRIVE AT DESIRED R AND R .
F
G
The Classical Noninverting Amplifier: High Input Z
1991 F04
WE PROVIDE YOU WITH <0.1% RESISTORS.
Perhaps the most common op amp configuration is the
noninverting amplifier. Figure 4 shows the textbook
Figure 4. The LT1991 as a Classical Noninverting Op Amp
1991fh
12
LT1991
APPLICATIONS INFORMATION
Table 1. Configuring the M Pins for Simple Noninverting Gains.
The P Inputs are driven as shown in the examples on the
next page
M9, M3, M1 Connection
Gain
1
M9
M3
M1
Output
Output
Output
Float
Output
Output
Float
Output
Ground
Ground
Ground
Output
Float
1.077
1.1
1.25
1.273
1.3
1.4
2
Output
Ground
Ground
Ground
Float
Output
Output
Output
Float
Ground
Ground
Output
Output
Float
2.5
2.8
3.25
3.5
4
Float
Ground
Output
Output
Output
Ground
Ground
Float
Ground
Ground
Ground
Float
Ground
Float
5
Float
Ground
Output
Output
Float
5.5
7
Ground
Ground
Ground
Ground
Ground
Ground
Ground
Float
10
11
Float
Ground
Float
13
Ground
Ground
14
Ground
1991fh
13
LT1991
APPLICATIONS INFORMATION
+
+
7
+
V
S
V
V
S
S
8
9
10
8
9
10
8
9
10
M9
M3
M1
M9
M3
M1
M9
M3
M1
7
7
V
V
V
CC
CC
CC
6
6
6
6
6
6
6
6
6
LT1991
V
V
V
LT1991
V
V
V
LT1991
V
V
V
OUT
REF
5
OUT
REF
5
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
1
2
3
1
2
3
1
2
3
REF
5
V
P1
P3
P9
P1
P3
P9
P1
P3
P9
IN
V
V
V
EE
EE
EE
V
V
IN
IN
4
4
4
–
V
S
–
–
V
S
V
S
GAIN = 1
GAIN = 2
GAIN = 3.25
+
V
+
+
7
S
V
V
S
S
8
9
10
8
9
10
8
9
10
M9
M3
M1
M9
M3
M1
M9
M3
M1
7
7
V
CC
V
CC
V
CC
LT1991
LT1991
LT1991
OUT
REF
5
OUT
REF
5
1
2
3
1
2
3
1
2
3
REF
5
P1
P3
P9
P1
P3
P9
P1
P3
P9
V
V
V
EE
EE
EE
4
4
4
–
–
–
V
S
V
S
V
S
V
V
V
IN
IN
IN
GAIN = 4
GAIN = 5
GAIN = 5.5
+
7
+
7
+
V
S
V
V
S
S
8
9
10
8
9
10
8
9
10
M9
M3
M1
M9
M3
M1
M9
M3
M1
7
V
CC
V
CC
V
CC
LT1991
LT1991
LT1991
OUT
REF
5
OUT
REF
5
1
2
3
1
2
3
1
2
3
REF
P1
P3
P9
P1
P3
P9
P1
P3
P9
5
V
V
V
EE
EE
EE
V
V
IN
IN
4
4
4
–
–
–
V
S
V
S
V
S
V
IN
GAIN = 7
GAIN = 10
GAIN = 11
+
+
V
S
V
S
8
9
10
8
9
10
M9
M3
M1
M9
M3
M1
7
7
V
V
CC
CC
6
6
LT1991
V
LT1991
V
OUT
OUT
OUT
OUT
1
2
3
1
2
3
REF
REF
5
P1
P3
P9
P1
P3
P9
5
V
V
EE
EE
V
IN
4
4
–
–
V
S
V
S
V
IN
1991 F05
GAIN = 13
GAIN = 14
Figure 5. Some Implementations of Classical Noninverting
Gains Using the LT1991. High Input Z Is Maintained
1991fh
14
LT1991
APPLICATIONS INFORMATION
Attenuation Using the P Input Resistors
Table 2. Configuring the P Pins for Various Attenuations.
Those Shown in Bold Are Functional Even When the Input Drive
Exceeds the Supplies.
Attenuation happens as a matter of fact in difference
amplifier configurations, but it is also used for reducing
peak signal level or improving input common mode range
even in single ended systems. When signal conditioning
indicates a need for attenuation, the LT1991 resistors are
ready at hand. The four precision resistors can provide
several attenuation levels, and these are tabulated in
Table 2 as a design reference.
P9, P3, P1, REF Connection
A
P9
P3
P1
Drive
Drive
Drive
Drive
Drive
Drive
Drive
Ground
Float
REF
0.0714
0.0769
0.0909
0.1
Ground
Ground
Ground
Ground
Ground
Ground
Float
Ground
Ground
Float
Ground
Float
Ground
Float
Float
0.143
0.182
0.2
Ground
Float
Drive
Drive
Ground
Drive
Ground
Ground
Ground
Float
V
IN
V
V
0.214
0.231
0.25
0.286
0.308
0.357
0.4
Ground
Ground
Float
456k
156k
56k
IN
INT
1
2
3
R
R
OKAY UP
TO ±±6V
+
A
Drive
4pF
V
INT
Ground
Drive
Drive
Drive
Drive
Drive
Drive
Drive
Ground
Ground
Float
G
V
= A • V
IN
INT
A = R /(R + R )
Ground
Ground
Ground
Float
Ground
Float
456k
G
A
G
LT1991
Drive
5
Drive
Drive
CLASSICAL ATTENUATOR
LT1991 ATTENUATING TO THE +INPUT BY
DRIVING AND GROUNDING AND FLOATING
Ground
Float
Drive
INPUTS R = 456k, R = 56k, SO A = 6.1.
A
G
0.5
Float
Ground
Ground
Ground
Ground
Ground
Ground
Float
1991 F6±
0.6
Float
Drive
Figure 6. LT1991 Provides for Easy Attenuation to the Op Amp’s
+Input. The P1 Input Can Be Taken Well Outside of the Supplies
0.643
0.692
0.714
0.75
Drive
Ground
Ground
Ground
Drive
Drive
Becausetheattenuationsandthenoninvertinggainsareset
independently, they can be combined. This provides high
gain resolution, about 340 unique gains between 0.077
and 14, as plotted in Figure 7. This is too large a number
to tabulate, but the designer can calculate achievable gain
by taking the vector product of the gains and attenuations
in Tables 1 and 2, and seeking the best match. Average
gain resolution is 1.5%, with a worst-case of 7%.
Drive
Drive
Float
Float
0.769
0.786
0.8
Drive
Ground
Ground
Drive
Drive
Drive
Drive
Ground
Ground
Float
Drive
Drive
Float
Ground
Ground
Ground
Ground
Ground
Ground
Ground
Drive
0.818
0.857
0.9
Drive
Float
Drive
Drive
Drive
Float
100
0.909
0.923
0.929
1
Drive
Float
Drive
Float
Drive
Drive
10
Drive
Drive
Drive
Drive
Drive
Drive
1
0.1
0.01
50
100
150
200
COUNT
300
0
250
350
1991 F07
Figure 7. Over 346 Unique Gain Settings Achievable with the
LT1991 by Combining Attenuation with Noninverting Gain
1991fh
15
LT1991
APPLICATIONS INFORMATION
Inverting Configuration
Table 3. Configuring the M Pins for Simple Inverting Gains
M9, M3, M1 Connection
The inverting amplifier, shown in Figure 8, is another clas-
sical op amp configuration. The circuit is actually identical
to the noninverting amplifier of Figure 4, except that V
and GND have been swapped. The list of available gains
is shown in Table 3, and some of the circuits are shown
in Figure 9. Noise gain is 1+|Gain|, as is the usual case for
inverting amplifiers. Again, for the best DC performance,
match the source impedance seen by the op amp inputs.
Gain
–0.077
–0.1
–0.25
–0.273
–0.3
–0.4
–1
M9
Output
Output
Float
M3
Output
Float
M1
Drive
Drive
Drive
Output
Float
IN
Output
Drive
Drive
Drive
Float
Output
Output
Output
Float
Drive
Drive
Output
Output
Float
R
F
–1.5
–1.8
–2.25
–2.5
–3
Float
Drive
Output
Output
Output
Drive
Drive
Float
Drive
Drive
Drive
Float
R
G
V
–
+
IN
Drive
Float
V
OUT
V
= GAIN • V
IN
–4
Float
Drive
Output
Output
Float
OUT
GAIN = – R /R
F
G
–4.5
–6
Drive
Drive
Drive
Drive
Drive
Drive
CLASSICAL INVERTING OP AMP CONFIGURATION.
YOU PROVIDE THE RESISTORS.
Drive
Float
–9
–10
Float
Drive
Float
–12
Drive
Drive
50k
450k
4pF
8
9
V
IN
–13
Drive
(DRIVE)
150k
450k
10
–
+
6
V
OUT
450k
150k
50k
1
2
3
4pF
450k
LT1991
5
CLASSICAL INVERTING OP AMP CONFIGURATION IMPLEMENTED
WITH LT1991. R = 225k, R = 50k, GAIN = –4.5.
F
G
GAIN IS ACHIEVED BY GROUNDING, FLOATING OR FEEDING BACK
THE AVAILABLE RESISTORS TO ARRIVE AT DESIRED R AND R .
F
G
1991 F08
WE PROVIDE YOU WITH <0.1% RESISTORS.
Figure 8. The LT1991 as a Classical Inverting Op Amp.
Note the Circuit Is Identical to the Noninverting Amplifier,
Except that VIN and Ground Have Been Swapped
1991fh
16
LT1991
APPLICATIONS INFORMATION
+
+
7
+
V
S
V
V
S
S
8
9
10
8
9
10
8
9
10
V
M9
M3
M1
M9
M3
M1
M9
M3
M1
IN
7
7
V
V
V
CC
CC
CC
V
V
IN
IN
6
6
6
6
6
6
6
LT1991
V
V
V
LT1991
V
V
V
LT1991
V
OUT
REF
5
OUT
REF
5
OUT
REF
5
OUT
OUT
OUT
OUT
OUT
OUT
OUT
1
2
3
1
2
3
1
2
3
P1
P3
P9
P1
P3
P9
P1
P3
P9
V
V
V
EE
EE
EE
4
4
4
–
V
S
–
–
V
S
V
S
GAIN = –0.25
GAIN = –1
GAIN = –2.25
+
V
+
+
7
S
V
V
S
S
8
9
10
8
9
10
8
9
10
M9
M3
M1
M9
M3
M1
M9
M3
M1
V
IN
7
7
V
IN
V
CC
V
CC
V
CC
V
IN
6
LT1991
LT1991
LT1991
V
OUT
REF
5
OUT
REF
5
OUT
REF
5
OUT
1
2
3
1
2
3
1
2
3
P1
P3
P9
P1
P3
P9
P1
P3
P9
V
V
V
EE
EE
EE
4
4
4
–
–
–
V
S
V
S
V
S
GAIN = –3
GAIN = –4
GAIN = –4.5
+
7
+
7
+
V
S
V
V
S
S
8
9
10
8
9
10
8
9
10
V
V
M9
M3
M1
M9
M3
M1
M9
M3
M1
V
IN
IN
IN
7
V
CC
V
CC
V
CC
6
LT1991
LT1991
LT1991
V
OUT
REF
5
OUT
REF
5
OUT
REF
5
OUT
1
2
3
1
2
3
1
2
3
P1
P3
P9
P1
P3
P9
P1
P3
P9
V
V
V
EE
EE
EE
4
4
4
–
–
–
V
S
V
S
V
S
GAIN = –6
GAIN = –9
GAIN = –10
+
+
V
S
V
S
8
9
10
8
9
10
V
M9
M3
M1
M9
M3
M1
IN
7
7
V
V
CC
CC
V
IN
6
6
LT1991
V
LT1991
V
OUT
OUT
REF
OUT
OUT
1
2
3
1
2
3
REF
5
P1
P3
P9
P1
P3
P9
5
V
V
EE
EE
4
4
–
–
V
S
V
S
1991 F09
GAIN = –12
GAIN = –13
Figure 9. It Is Simple to Get Precision Inverting Gains with the LT1991.
Input Impedance Varies from 45kΩ (Gain = –13) to 450kΩ (Gain = –1)
1991fh
17
LT1991
APPLICATIONS INFORMATION
Difference Amplifiers
R
F
The resistors in the LT1991 allow it to easily make differ-
ence amplifiers also. Figure 10 shows the basic 4-resistor
difference amplifier and the LT1991. A difference gain of
3 is shown, but notice the effect of the additional dashed
connections. By connecting the 450k resistors in paral-
lel, the gain is reduced by a factor of 2. Of course, with
so many resistors, there are many possible gains. Table
4 shows the difference gains and how they are achieved.
Note that, as for inverting amplifiers, the noise gain is 1
more than the signal gain.
R
R
G
–
+
V
V
–
+
IN
IN
V
OUT
G
–
V
= GAIN • (V + – V
)
IN
OUT
IN
GAIN = R /R
R
F
G
F
CLASSICAL DIFFERENCE AMPLIFIER USING THE LT1991
50k
450k
4pF
8 M9
Table 4. Connections Giving Difference Gains for the LT1991
150k
450k
M3
9
–
V
IN
+
–
Gain
0.077
0.1
0.25
0.273
0.3
0.4
1
V
IN
V
Output
M3, M9
M9
GND (REF)
P3, P9
P9
IN
10 M1
P1
P1
M1
M1
–
+
PARALLEL
TO CHANGE
R , R
6
5
V
OUT
450k
150k
50k
1
2
3
F
G
P1
P3
P9
P1
M1
M3
P3
4pF
P3
M3
M1, M9
M9
P1, P9
P9
+
V
IN
P3
M3
450k
P1, P3
P1
M1, M3
M1
M9
P9
LT1991
1.5
1.8
2.25
2.5
3
P3
M3
M1
M1, M3
M3
P1
P1, P3
P3
CLASSICAL DIFFERENCE AMPLIFIER IMPLEMENTED
WITH LT1991. R = 450k, R = 150k, GAIN = 3.
P9
M9
F
G
P9
M9
ADDING THE DASHED CONNECTIONS CONNECTS THE
P1, P9
P3
M1, M9
M3
M3
P3
TWO 450k RESISTORS IN PARALLEL, SO R IS REDUCED
F
TO 225k. GAIN BECOMES 225k/150k = 1.5.
1991 F10
4
P1, P3
P9
M1, M3
M9
Figure 10. Difference Amplifier Using the LT1991. Gain Is Set
Simply by Connecting the Correct Resistors or Combinations
of Resistors. Gain of 3 Is Shown, with Dashed Lines Modifying
It to Gain of 1.5. Noise Gain Is Optimal
4.5
6
M1
M1
P1
P1
P3, P9
P9
M3, M9
M9
9
10
P1, P9
P3, P9
M1, M9
M3, M9
12
13
P1, P3, P9 M1, M3, M9
1991fh
18
LT1991
APPLICATIONS INFORMATION
+
+
7
+
V
S
V
V
S
S
8
9
10
8
9
10
8
9
10
–
V
V
M9
M3
M1
M9
M3
M1
M9
M3
M1
IN
IN
7
7
V
V
V
CC
CC
CC
–
+
–
+
V
V
V
V
IN
IN
IN
6
6
6
6
6
6
6
LT1991
V
V
V
LT1991
V
V
V
LT1991
V
V
V
OUT
REF
5
OUT
REF
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
1
2
3
1
2
3
1
2
3
REF
P1
P3
P9
P1
P3
P9
P1
P3
P9
IN
5
5
V
V
V
EE
EE
EE
+
4
4
4
–
–
V
V
S
–
S
V
S
GAIN = 0.25
GAIN = 1
GAIN = 2.25
+
V
+
+
7
S
V
V
S
S
8
9
10
8
9
10
8
9
10
–
V
M9
M3
M1
M9
M3
M1
M9
M3
M1
IN
7
7
–
+
–
+
V
V
V
V
IN
IN
IN
IN
V
V
V
CC
CC
CC
6
LT1991
LT1991
LT1991
OUT
REF
5
OUT
REF
1
2
3
1
2
3
1
2
3
REF
P1
P3
P9
P1
P3
P9
P1
P3
P9
5
5
V
V
V
EE
EE
EE
+
V
IN
4
4
4
–
–
V
V
S
–
S
V
S
GAIN = 3
GAIN = 4
GAIN = 4.5
+
7
+
7
+
V
S
V
V
S
S
–
–
–
8
9
10
8
9
10
8
9
10
V
V
V
V
V
V
IN
IN
IN
IN
IN
M9
M3
M1
M9
M3
M1
M9
M3
M1
7
V
V
V
CC
CC
CC
6
LT1991
LT1991
LT1991
OUT
REF
5
OUT
REF
1
2
3
1
2
3
1
2
3
REF
P1
P3
P9
P1
P3
P9
P1
P3
P9
5
5
V
V
V
EE
EE
EE
+
+
+
IN
4
4
4
–
–
–
V
S
V
S
V
S
GAIN = 6
GAIN = 9
V
GAIN = 10
+
+
V
V
S
S
–
8
9
10
–
8
9
10
V
IN
M9
M3
M1
IN
M9
M3
M1
7
7
V
V
CC
CC
6
6
LT1991
V
LT1991
V
OUT
OUT
REF
OUT
REF
OUT
1
2
3
1
2
3
P1
P3
P9
P1
P3
P9
5
5
V
V
EE
EE
+
+
V
V
IN
IN
4
4
–
–
V
S
V
S
1991 F11
GAIN = 12
GAIN = 13
Figure 11. Many Difference Gains Are Achievable Just by Strapping the Pins
1991fh
19
LT1991
APPLICATIONS INFORMATION
50k
450k
4pF
M9
M3
M1
8
150k
450k
9
–
V
IN
R
F
10
–
+
CROSS-
6
5
V
OUT
COUPLING
R
R
450k
150k
50k
G
1
P1
–
+
V
V
–
+
IN
V
OUT
4pF
2 P3
+
G
V
IN
IN
–
V
= GAIN • (V + – V
)
IN IN
OUT
GAIN = R /R
450k
R
F
F
G
P9
3
LT1991
CLASSICAL DIFFERENCE AMPLIFIER IMPLEMENTED
WITH LT1991. R = 450k, R = 150k, GAIN = 3.
CLASSICAL DIFFERENCE AMPLIFIER
F
G
GAIN CAN BE ADJUSTED BY "CROSS COUPLING." MAKING THE
DASHED CONNECTIONS REDUCE THE GAIN FROM 3 T0 2.
WHEN CROSS COUPLING, SEE WHAT IS CONNECTED TO THE
V
IN
+ VOLTAGE. CONNECTING P3 AND M1 GIVES +3 –1 = 2.
CONNECTIONS TO V – ARE SYMMETRIC: M3 AND P1.
1991 F12
IN
Figure 12. Another Method of Selecting Difference Gain Is “Cross-Coupling.”
The Additional Method Means the LT1991 Provides All Integer Gains from 1 to 13
+
Difference Amplifier: Additional Integer Gains Using
Cross-Coupling
V
+
V
S
S
8
9
10
8
9
10
–
M9
M3
M1
V
M9
M3
M1
IN
7
7
–
V
V
IN
IN
V
V
CC
CC
6
6
Figure 12 shows the basic difference amplifier as well as
the LT1991 in a difference gain of 3. But notice the effect
of the additional dashed connections. This is referred to
as “cross-coupling” and has the effect of reducing the
differential gain from 3 to 2. Using this method, additional
integer gains are achievable, as shown in Table 5 below,
so that all integer gains from 1 to 13 are achieved with the
LT1991.Notethattheequationscanbewrittenbyinspection
LT1991
V
LT1991
V
OUT
OUT
REF
5
OUT
REF
OUT
1
2
3
1
2
3
P1
P3
P9
P1
P3
P9
+
5
V
V
V
EE
EE
+
V
IN
4
4
–
–
V
S
S
GAIN = 2
GAIN = 5
+
+
V
V
S
S
–
–
8
9
10
8
9
10
V
V
V
IN
IN
M9
M3
M1
M9
M3
M1
7
7
V
V
CC
CC
6
6
LT1991
V
LT1991
V
OUT
OUT
REF
5
OUT
REF
OUT
1
2
3
1
2
3
+
–
P1
P3
P9
P1
P3
P9
from the V connections, and that the V connections
IN
IN
5
V
V
V
EE
EE
+
V
IN
+
are simply the opposite (swap P for M and M for P). Noise
gain,bandwidth,andinputimpedancespecificationsforthe
various cases are also tabulated, as these are not obvious.
Schematics are provided in Figure 13.
4
4
IN
–
–
V
S
S
GAIN = 7
GAIN = 8
+
7
V
S
–
8
9
10
V
V
IN
M9
M3
M1
V
CC
Table 5. Connections Using Cross-Coupling. Note That Equations Can
6
+
LT1991
V
OUT
OUT
REF
Be Written by Inspection of the V Column
IN
1
2
3
P1
P3
P9
+
–
5
V
Noise –3dB BW
R
R
IN
EE
IN
+
+
–
IN
4
–
Gain
2
V
V
Equation Gain
3 – 1
P9, M3, M1 M9, P3, P1 9 – 3 – 1 14
P9, M3 M9, P3 9 – 3 13
P9, P1, M3 M9, M1, P3 9 + 1 – 3 14
P9, M1 M9, P1 9 – 1 11
kHz
70
32
35
32
38
32
Typ kΩ Typ kΩ
IN
IN
V
S
P3, M1
M3, P1
5
281
97
141
49
49
44
50
37
1991 F13
GAIN = 11
5
6*
7
122
121
248
242
Figure 13. Integer Gain Difference
Amplifiers Using Cross-Coupling
8
11 P9, P3, M1 M9, M3, P1 9 + 3 – 1 14
*Gain of 6 is better implemented as shown previously, but is included here for completeness.
1991fh
20
LT1991
APPLICATIONS INFORMATION
High Voltage CM Difference Amplifiers
Table 6. HighV CM Connections Giving Difference Gains for
the LT1991
This class of difference amplifier remains to be discussed.
Figure 14 shows the basic circuit on the top. The effective
input voltage range of the circuit is extended by the fact
Max, Min V
EXT
Noise
Gain
(Substitute V – 1.2,
CC
+
–
Gain
V
V
R
T
V
+ 1 for V
)
IN
IN
EE
LIM
thatresistorsR attenuatethecommonmodevoltageseen
1
1
1
1
P1
P1
P1
P1
M1
2
5
2 • V - V
LIM REF
T
by the op amp inputs. For the LT1991, the most useful
M1 P3, M3
M1 P9, M9
5 • V – V – 3 • V
LIM REF TERM
resistors for R are the M1 and P1 450kΩ resistors, be-
11
14
11 • V – V – 9 • V
LIM REF TERM
G
cause they do not have diode clamps to the supplies and
therefore can be taken outside the supplies. As before, the
input CM of the op amp is the limiting factor and is set by
M1
P3||P9
14 • V – V – 12 • V
LIM REF TERM
M3||M9
R
F
the voltage at the op amp +input, V . By superposition
INT
we can write:
V
CC
R
R
G
V
= V • (R ||R )/(R + R ||R ) + V • (R ||R )/
INT
EXT
F
T
G
F
T
REF
G
T
–
+
V
–
+
IN
V
(R + R ||R ) + V
• (R ||R )/(R + R ||R )
F G T F G
OUT
F
G
T
TERM
G
V
(= V
IN
–
)
EXT
V
= GAIN • (V + – V
IN
)
OUT
IN
Solving for V
:
EXT
GAIN = R /R
F
G
V
R
T
R
T
EE
R
F
V
EXT
= (1 + R /(R ||R )) • (V – V • (R ||R )/
G F T INT REF G T
V
REF
V
TERM
(R + R ||R ) – V
• (R ||R )/(R + R ||R ))
F G T F G
F
G
T
TERM
HIGH CM VOLTAGE DIFFERENCE AMPLIFIER
Given the values of the resistors in the LT1991, this equa-
tion has been simplified and evaluated, and the resulting
equations provided in Table 6. As before, substituting
INPUT CM TO OP AMP IS ATTENUATED BY
RESISTORS R CONNECTED TO V
T
TERM.
7
12V
V
– 1.2 and V + 1 for V
will give the valid upper
CC
EE
LIM
50k
450k
4pF
8 M9
andlowercommonmodeextremesrespectively.Following
are sample calculations for the case shown in Figure 14,
right-hand side. Note that P9 and M9 are terminated so
row 3 of Table 6 provides the equation:
150k
450k
M3
9
10 M1
–
6
5
V
MAX V = 11 • (V – 1.2V) – V – 9 • V
TERM
OUT
EXT
CC
REF
450k
150k
50k
1
2
3
P1
P3
P9
+
= 11 • (10.8V) – 2.5 – 9 • 12 = 8.3V
–
+
V
V
IN
IN
4pF
INPUT CM RANGE
= –60V TO 8.3V
and:
MIN V = 11 • (V + 1V) – V – 9 • V
TERM
450k
REF
2.5V
EXT
EE
REF
LT1991
4
= 11 • (1V) – 2.5 – 9 • 12 = –99.5V
HIGH NEGATIVE CM VOLTAGE DIFFERENCE AMPLIFIER
IMPLEMENTED WITH LT1991.
but this exceeds the 60V absolute maximum rating of
the P1, M1 pins, so –60V becomes the de facto negative
common mode limit. Several more examples of high CM
circuitsareshowninFigures15,16,17forvarioussupplies.
R = 450k, R = 450k, R 50k, GAIN = 1
F
G
T
1991 F14
V
= V = 12V, V
CC
= 2.5V, V = GROUND.
REF EE
TERM
Figure 14. Extending CM Input Range
1991fh
21
LT1991
APPLICATIONS INFORMATION
3V
3V
3V
8
9
10
8
9
10
8
9
10
M9
M3
M1
M9
M3
M1
M9
M3
M1
7
7
7
V
V
V
CC
CC
CC
–
+
–
+
–
+
V
V
V
V
V
V
IN
IN
IN
IN
IN
IN
6
6
6
LT1991
V
LT1991
V
LT1991
V
OUT
OUT
REF
OUT
REF
OUT
REF
OUT
OUT
1
2
3
1
2
3
1
2
3
P1
P3
P9
P1
P3
P9
P1
P3
P9
5
5
5
V
V
V
EE
EE
EE
1.25V
4
4
4
3V
V
= 0.8V TO 2.35V
V
CM
V
= 2V TO 3.6V
DM
V
= –1V TO 0.6V
DM
CM
CM
V
> 40mV
<–40mV
3V
3V
7
3V
7
3V
7
8
9
8
9
10
8
9
10
M9
M3
M1
M9
M3
M1
M9
M3
M1
V
CC
V
CC
V
CC
10
–
–
–
V
V
V
V
V
V
IN
IN
IN
IN
IN
IN
6
6
6
LT1991
V
LT1991
V
OUT
V
OUT
V
OUT
LT1991
V
OUT
OUT
REF
OUT
REF
OUT
REF
OUT
OUT
OUT
1
2
3
1
2
3
1
2
3
+
+
+
P1
P3
P9
P1
P3
P9
P1
P3
P9
5
5
5
V
V
V
EE
EE
EE
1.25V
1.25V
1.25V
4
4
4
1.25V
V
= 0V TO 4V
V
= 3.8V TO 7.75V
V = –5V TO –1.25V
CM
CM
CM
3V
3V
7
3V
7
3V
7
8
9
8
9
10
8
9
10
M9
M3
M1
M9
M3
M1
M9
M3
M1
V
CC
V
CC
V
CC
10
–
+
–
+
–
+
V
V
V
V
V
V
IN
IN
IN
IN
IN
IN
6
6
6
LT1991
V
LT1991
LT1991
V
OUT
OUT
REF
OUT
REF
OUT
REF
1
2
3
1
2
3
1
2
3
P1
P3
P9
P1
P3
P9
P1
P3
P9
5
5
5
V
V
V
EE
EE
EE
1.25V
1.25V
1.25V
4
4
4
1.25V
V
= –1.5V TO 7.2V
V
= 9.8V TO 18.55V
V = –17.2V TO –8.45V
CM
CM
CM
3V
3V
7
3V
7
3V
7
8
9
8
9
10
8
9
10
M9
M3
M1
M9
M3
M1
M9
M3
M1
V
CC
V
CC
V
CC
10
–
–
+
–
V
V
V
IN
IN
IN
IN
IN
6
6
6
LT1991
V
LT1991
LT1991
V
OUT
OUT
REF
OUT
REF
OUT
REF
1
2
3
1
2
3
1
2
3
+
+
V
V
V
IN
P1
P3
P9
P1
P3
P9
P1
P3
P9
5
5
5
V
V
V
EE
EE
EE
1.25V
1.25V
1.25V
4
4
4
1.25V
V
= –2.25V TO 8.95V
V
= 12.75V TO 23.95V
V
= –23.2V TO –12V
CM
CM
CM
1991 F15
Figure 15. Common Mode Ranges for Various LT1991 Configurations on VS = 3V, 0V; with Gain = 1
1991fh
22
LT1991
APPLICATIONS INFORMATION
5V
5V
5V
8
9
10
8
9
10
8
9
10
M9
M3
M1
M9
M3
M1
M9
M3
M1
7
7
7
V
V
V
CC
CC
CC
–
+
–
+
–
+
V
V
V
V
V
V
IN
IN
IN
IN
IN
IN
6
6
6
6
6
6
LT1991
V
LT1991
V
LT1991
V
OUT
OUT
REF
OUT
REF
OUT
REF
OUT
OUT
1
2
3
1
2
3
1
2
3
P1
P3
P9
P1
P3
P9
P1
P3
P9
5
5
5
V
V
V
EE
EE
EE
2.5V
4
4
4
3V
V
= –0.5V TO 5.1V
V
= 2V TO 7.6V
> 40mV
V
= –3V TO 2.6V
<–40mV
CM
CM
V
CM
V
DM
DM
5V
5V
7
5V
7
5V
7
8
9
10
8
9
10
8
9
10
M9
M3
M1
M9
M3
M1
M9
M3
M1
V
V
V
CC
CC
CC
–
–
–
V
V
V
V
V
V
IN
IN
IN
IN
IN
IN
6
6
6
6
LT1991
V
LT1991
V
OUT
V
OUT
V
OUT
LT1991
V
OUT
OUT
REF
OUT
REF
OUT
REF
OUT
OUT
OUT
1
2
3
1
2
3
1
2
3
+
+
+
P1
P3
P9
P1
P3
P9
P1
P3
P9
5
5
5
V
V
V
EE
EE
EE
2.5V
2.5V
2.5V
4
4
4
2.5V
V
= –5V TO 9V
V
= 2.5V TO 16.5V
V = –12.5V TO 1.5V
CM
CM
CM
5V
5V
7
5V
7
5V
7
8
9
10
8
9
10
8
9
10
M9
M3
M1
M9
M3
M1
M9
M3
M1
V
V
V
CC
CC
CC
–
+
–
+
–
+
V
V
V
V
V
V
IN
IN
IN
IN
IN
IN
6
LT1991
V
LT1991
LT1991
V
OUT
OUT
REF
OUT
REF
OUT
REF
1
2
3
1
2
3
1
2
3
P1
P3
P9
P1
P3
P9
P1
P3
P9
5
5
5
V
V
V
EE
EE
EE
2.5V
2.5V
2.5V
4
4
4
2.5V
V
= –14V TO 16.8V
V
= 8.5V TO 39.3V
V = –36.5V TO –5.7V
CM
CM
CM
5V
5V
7
5V
7
5V
7
8
9
10
8
9
10
8
9
10
M9
M3
M1
M9
M3
M1
M9
M3
M1
V
V
V
CC
CC
CC
–
+
–
+
–
V
V
V
IN
IN
IN
IN
IN
IN
6
LT1991
V
LT1991
LT1991
V
OUT
OUT
REF
OUT
REF
OUT
REF
1
2
3
1
2
3
1
2
3
+
V
V
V
P1
P3
P9
P1
P3
P9
P1
P3
P9
5
5
5
V
V
V
EE
EE
EE
2.5V
2.5V
2.5V
4
4
4
2.5V
V
= –18.5V TO 20.7V
V
= 11.5V TO 50.7V
V
= –48.5V TO –9.3V
CM
CM
CM
1991 F16
Figure 16. Common Mode Ranges for Various LT1991 Configurations on VS = 5V, 0V; with Gain = 1
1991fh
23
LT1991
APPLICATIONS INFORMATION
5V
5V
5V
8
9
10
8
9
10
8
9
10
M9
M3
M1
M9
M3
M1
M9
M3
M1
7
7
7
V
V
V
CC
CC
CC
–
+
–
+
–
+
V
V
V
V
V
V
IN
IN
IN
IN
IN
IN
6
6
6
6
6
6
6
6
6
6
6
6
LT1991
V
LT1991
V
LT1991
V
OUT
OUT
REF
OUT
REF
OUT
REF
OUT
OUT
1
2
3
1
2
3
1
2
3
P1
P3
P9
P1
P3
P9
P1
P3
P9
5
5
5
V
V
V
EE
EE
EE
4
4
4
–5V
–5V
–5V
–5V
–5V
V
= –8V TO 7.6V
V
= –3V TO 12.6V
V
= –13V TO 2.6V
<–40mV
DM
CM
CM
V
CM
V
> 40mV
DM
5V
5V
7
5V
7
5V
7
8
9
10
8
9
10
8
9
10
M9
M3
M1
M9
M3
M1
M9
M3
M1
V
V
V
CC
CC
CC
–
+
–
–
+
V
V
V
V
V
V
IN
IN
IN
IN
IN
IN
LT1991
V
LT1991
V
OUT
V
OUT
V
OUT
LT1991
V
OUT
OUT
REF
OUT
REF
OUT
REF
OUT
OUT
OUT
1
2
3
1
2
3
1
2
3
+
P1
P3
P9
P1
P3
P9
P1
P3
P9
5
5
5
V
V
V
EE
EE
EE
4
4
4
–5V
–5V
–5V
–5V
V
= –20V TO 19V
V
= –5V TO 34V
V = –35V TO 4V
CM
CM
CM
5V
5V
7
5V
7
5V
7
8
9
10
8
9
10
8
9
10
M9
M3
M1
M9
M3
M1
M9
M3
M1
V
V
V
CC
CC
CC
–
+
–
+
–
+
V
V
V
V
V
V
IN
IN
IN
IN
IN
IN
LT1991
V
LT1991
LT1991
V
OUT
OUT
REF
OUT
REF
OUT
REF
1
2
3
1
2
3
1
2
3
P1
P3
P9
P1
P3
P9
P1
P3
P9
5
5
5
V
V
V
EE
EE
EE
4
4
4
–5V
–5V
–5V
–5V
V
= –44V TO 41.8V
V
= 1V TO 60V
V = –60V TO –3.2V
CM
CM
CM
5V
5V
7
5V
7
5V
7
8
9
10
8
9
10
8
9
10
M9
M3
M1
M9
M3
M1
M9
M3
M1
V
V
V
CC
CC
CC
–
+
–
+
–
V
V
V
IN
IN
IN
IN
IN
IN
LT1991
V
LT1991
LT1991
V
OUT
OUT
REF
OUT
REF
OUT
REF
1
2
3
1
2
3
1
2
3
+
V
V
V
P1
P3
P9
P1
P3
P9
P1
P3
P9
5
5
5
V
V
V
EE
EE
EE
4
4
4
–5V
–5V
= 4V TO 60V
–5V
= –56V TO 53.2V
–5V
= –60V TO –6.8V
V
V
V
CM
CM
CM
1991 F17
Figure 17. Common Mode Ranges for Various LT1991 Configurations on VS = 5V, with Gain = 1
1991fh
24
LT1991
TYPICAL APPLICATIONS
Micropower AV = 10 Instrumentation Amplifier
V
OUT
10
9
8
7
6
+
V
M
1/2 LT6011
–
4pF
–
+
+
LT1991
V
P
1/2 LT6011
–
4pF
1
2
3
4
5
1991 TA02
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
DD Package
10-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1699 Rev C)
R = 0.125
0.40 ± 0.10
TYP
6
10
0.70 ±0.05
3.55 ±0.05
2.15 ±0.05 (2 SIDES)
1.65 ±0.05
3.00 ±0.10 1.65 ± 0.10
(4 SIDES) (2 SIDES)
PACKAGE
OUTLINE
PIN 1 NOTCH
R = 0.20 OR
0.35 × 45°
PIN 1
TOP MARK
(SEE NOTE 6)
CHAMFER
(DD) DFN REV C 0310
5
1
0.25 ± 0.05
0.50 BSC
0.75 ±0.05
0.200 REF
0.25 ± 0.05
0.50
BSC
2.38 ±0.10
(2 SIDES)
2.38 ±0.05
(2 SIDES)
0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
NOTE:
1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2).
CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE
1991fh
25
LT1991
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
MS Package
10-Lead Plastic MSOP
(Reference LTC DWG # 05-08-ꢀꢂꢂꢀ Rev E)
0.889 0.ꢀꢁ7
(.035 .005)
5.ꢁ3
3.ꢁ0 – 3.45
(.ꢁ0ꢂ)
(.ꢀꢁꢂ – .ꢀ3ꢂ)
MIN
3.00 0.ꢀ0ꢁ
(.ꢀꢀ8 .004)
(NOTE 3)
0.497 0.07ꢂ
(.0ꢀ9ꢂ .003)
REF
0.50
(.0ꢀ97)
BSC
0.305 0.038
(.0ꢀꢁ0 .00ꢀ5)
TYP
ꢀ0 9
8
7 ꢂ
RECOMMENDED SOLDER PAD LAYOUT
3.00 0.ꢀ0ꢁ
(.ꢀꢀ8 .004)
(NOTE 4)
4.90 0.ꢀ5ꢁ
(.ꢀ93 .00ꢂ)
DETAIL “A”
0.ꢁ54
(.0ꢀ0)
0° – ꢂ° TYP
GAUGE PLANE
ꢀ
ꢁ
3
4 5
0.53 0.ꢀ5ꢁ
(.0ꢁꢀ .00ꢂ)
0.8ꢂ
(.034)
REF
ꢀ.ꢀ0
(.043)
MAX
DETAIL “A”
0.ꢀ8
(.007)
SEATING
PLANE
0.ꢀ7 – 0.ꢁ7
(.007 – .0ꢀꢀ)
TYP
0.ꢀ0ꢀꢂ 0.0508
(.004 .00ꢁ)
0.50
(.0ꢀ97)
BSC
MSOP (MS) 0307 REV E
NOTE:
ꢀ. DIMENSIONS IN MILLIMETER/(INCH)
ꢁ. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.ꢀ5ꢁmm (.00ꢂ") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.ꢀ5ꢁmm (.00ꢂ") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.ꢀ0ꢁmm (.004") MAX
1991fh
26
LT1991
REVISION HISTORY (Revision history begins at Rev H)
REV
DATE
DESCRIPTION
PAGE NUMBER
H
5/12
Corrected specified temperature range for C-grade parts in the Order Information table.
2
Corrected V = –20V to 19V and V = –5V to 34V configurations in Figure 17.
24
28
CM
CM
Updated Related Parts Table
1991fh
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
27
LT1991
TYPICAL APPLICATION
Bidirectional Current Source
Single Supply AC Coupled Amplifier
+
V
V
= 2.7V TO 36V
7
S
S
8
9
10
8
9
10
M9
M3
M1
M9
M3
M1
7
1µF
–
V
V
IN
IN
6
6
LT1991
4
LT1991
V
OUT
1
2
3
1
2
3
+
R1
P1
P3
P9
V
CC
P1
P3
P9
0.1µF
R2*
10k
5
10k
5
V
IN
4
+ –
–
V
IN
V
IN
I
=
LOAD
–
V
10kΩ
S
GAIN = 12
*SHORT R2 FOR LOWEST OUTPUT
OFFSET CURRENT. INCLUDE R2 FOR
HIGHEST OUTPUT IMPEDANCE.
BW = 7Hz TO 32kHz
1991 TA03
Ultra-Stable Precision Attenuator
Analog Level Adaptor
5V
8
9
1ꢀ
5V
M9
M3
M1
7
8
9
1ꢀ
M9
M3
M1
7
6
LT1991
ꢀ-4V
OUT
6
1
2
3
V
13
REF
5
IN
1ꢀV
P1
P3
P9
LT1991
V
=
IN
OUT
1
2
3
V
REF
5
IN
P1
P3
P9
= 14V to 53V
4
4
–5V
LT179ꢀ –2.5
1µF
5V
6
4
2
1991 TAꢀ4
1
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LT1990
High Voltage, Gain Selectable Difference Amplifier
Precision Gain Selectable Difference Amplifier
High Speed, Gain Selectable Difference Amplifier
250V Common Mode, Micropower, Pin Selectable Gain = 1, 10
Micropower, Pin Selectable Up to Gain = 118
LT1996
LT1995
30MHz, 1000V/µs, Pin Selectable Gain = –7 to 8
LT6010/LT6011/
LT6012
Single/Dual/Quad 135µA 14nV/√Hz Rail-to-Rail Out
Precision Op Amp
Similar Op Amp Performance as Used in LT1991 Difference Amplifier
LT6013/LT6014
Single/Dual 145µA 8nV/√Hz Rail-to-Rail Out
Precision Op Amp
Lower Noise A ≥ 5 Version of LT1991 Type Op Amp
V
LTC6910-X
LT1999
Programmable Gain Amplifiers
3 Gain Configurations, Rail-to-Rail Input and Output
CMRR > 80dB at 100kHz
High Voltage Bidirectional Current Sense Amplifier
Quad Matched Resistor Network
LT5400
0.01% Matching, CMRR > 86dB
1991fh
LT 0512 REV H • PRINTED IN USA
28 LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
l
l
LINEAR TECHNOLOGY CORPORATION 2006
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
相关型号：
LTC6911HMS-1#TR
LTC6911 - Dual Matched Amplifiers with Digitally Programmable Gain in MSOP; Package: MSOP; Pins: 10; Temperature Range: -40°C to 125°C
Linear
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