LT1991 Datasheet by Analog Devices Inc.

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L7L|nl Hp LT1991 TECHNOLOGY f | |+| a; .%V ? L7 LJUW 1
LT1991
1
1991fh
+
5V
∆VIN
VM(IN)
VP(IN)
+
VOUT = VREF + ∆VIN
SWING 40mV TO
EITHER RAIL
ROUT <0.1Ω
VREF = 2.5V
INPUT RANGE
–0.5V TO 5.1V
RIN = 900kΩ
LT1991
1991 TA01
50k
50k
150k
150k
450k
450k
4pF
450k
450k
4pF
FEATURES
APPLICATIONS
DESCRIPTION
Precision, 100µA
Gain Selectable Amplifier
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
external components. The device is particularly well suited
for use as a difference amplifier, where the excellent resis-
tor matching results in a common mode rejection ratio of
greater than 75dB.
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.
The resistors have excellent matching, 0.04% over tem-
perature for the 450k resistors. The matching temperature
coefficient is guaranteed less than 3ppm/°C. The resis-
tors are extremely linear with voltage, resulting in a gain
nonlinearity of less than 10ppm.
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.
Rail-to-Rail Gain = 1 Difference Amplifier
n Pin Configurable as a Difference Amplifier,
Inverting and Noninverting Amplifier
n Difference Amplifier
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
n Gain Error <0.04%
n Gain Drift < 3ppm/°C
n Wide Supply Range: Single 2.7V to Split ±18V
n Micropower: 100µA Supply Current
n Precision: 50µV Maximum Input Offset Voltage
n 560kHz Gain Bandwidth Product
n Rail-to-Rail Output
n Space Saving 10-Lead MSOP and DFN Packages
n Handheld Instrumentation
n Medical Instrumentation
n Strain Gauge Amplifiers
n Differential to Single-Ended Conversion
RESISTOR MATCHING (%)
PERCENTAGE OF UNITS (%)
0.04
1991 TA01b
–0.02 00.02
40
35
30
25
20
15
10
5
0
–0.04
450k RESISTORS
LT1991A
Distribution of Resistor Matching
L, LT, LTC and LT M are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
LT1991 jjjjj TDP vwEw CECE:
LT1991
2
1991fh
ABSOLUTE MAXIMUM RATINGS
Total Supply Voltage (V+ to V) ................................40V
Input Voltage (Pins P1/M1, Note 2) ........................±60V
Input Voltage
(Other Inputs Note 2) ..................V+ + 0.2V to V 0.2V
Output Short-Circuit Duration (Note 3) ........... Indefinite
Operating Temperature Range (Note 4)
LT1991C ...............................................40°C to 8C
LT1991I ................................................ 40°C to 85°C
LT1991H ............................................. 40°C to 125°C
(Note 1) Specified Temperature Range (Note 5)
LT1991C ...............................................40°C to 8C
LT1991I ................................................ 40°C to 85°C
LT1991H ............................................. 40°C to 125°C
Maximum Junction Temperature
DD Package ......................................................... 125°C
MS Package ......................................................... 150°C
Storage Temperature Range
DD Package ........................................... 65°C to 125°C
MS Package ........................................... 6C to 150°C
Lead Temperature (Soldering, 10 sec) ..................300°C
LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION SPECIFIED TEMPERATURE RANGE
LT1991CDD#PBF LTCT1991CDD#TRPBF LBMM 10-Lead (3mm × 3mm) Plastic DFN 0°C to 70°C
LT1991ACDD#PBF LT1991ACDD#TRPBF LBMM 10-Lead (3mm × 3mm) Plastic DFN 0°C to 70°C
LT1991IDD#PBF LT1991IDD#TRPBF LBMM 10-Lead (3mm × 3mm) Plastic DFN –40°C to 85°C
LT1991AIDD#PBF LT1991AIDD#TRPBF LBMM 10-Lead (3mm × 3mm) Plastic DFN –40°C to 85°C
LT1991HDD#PBF LT1991HDD#TRPBF LBMM 10-Lead (3mm × 3mm) Plastic DFN –40°C to 125°C
LT1991CMS#PBF LT1991CMS#TRPBF LTQD 10-Lead Plastic MSOP 0°C to 70°C
LT1991ACMS#PBF LT1991ACMS#TRPBF LTQD 10-Lead Plastic MSOP 0°C to 70°C
LT1991IMS#PBF LT1991IMS#TRPBF LTQD 10-Lead Plastic MSOP –40°C to 85°C
LT1991AIMS#PBF LT1991AIMS#TRPBF LTQD 10-Lead Plastic MSOP –40°C to 85°C
LT1991HMS#PBF LT1991HMS#TRPBF LTQD 10-Lead Plastic MSOP –40°C to 125°C
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/
TOP VIEW
DD PACKAGE
10-LEAD (3mm × 3mm) PLASTIC DFN
10
9
6
7
8
4
5
3
2
1M1
M3
M9
VCC
OUT
P1
P3
P9
VEE
REF
EXPOSED PAD CONNECTED TO VEE PCB
CONNECTION OPTIONAL
TJMAX = 125°C, qJA = 43°C/W
1
2
3
4
5
P1
P3
P9
VEE
REF
10
9
8
7
6
M1
M3
M9
VCC
OUT
TOP VIEW
MS PACKAGE
10-LEAD PLASTIC MSOP
TJMAX = 150°C, qJA = 230°C/W
PIN CONFIGURATION
ORDER INFORMATION
LT1991 L7 LJUW 3
LT1991
3
1991fh
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.
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
∆G Gain Error VS = ±15V, VOUT = ±10V; RL = 10k
G = 1; LT1991A
G = 1; LT1991
G = 3 or 9; LT1991A
G = 3 or 9; LT1991
l
l
l
l
±0.04
±0.08
±0.06
±0.12
%
%
%
%
GNL Gain Nonlinearity VS = ±15V; VOUT = ±10V; RL = 10k l1 10 ppm
∆G/∆T Gain Drift vs Temperature (Note 6) VS = ±15V; VOUT = ±10V; RL = 10k l0.3 3 ppm/°C
CMRR Common Mode Rejection Ratio,
Referred to Inputs (RTI)VS = ±15V; VCM = ±15.2V
G = 9; LT1991A
G = 3; LT1991A
G = 1; LT1991A
Any Gain; LT1991
l
l
l
l
80
75
75
60
100
93
90
70
dB
dB
dB
dB
VCM Input Voltage Range (Note 7) P1/M1 Inputs
VS = ±15V; VREF = 0V
VS = 5V, 0V; VREF = 2.5V
VS = 3V, 0V; VREF = 1.25V
l
l
l
–28
–0.5
0.75
27.6
5.1
2.35
V
V
V
P1/M1 Inputs, P9/M9 Connected to REF
VS = ±15V; VREF = 0V
VS = 5V, 0V; VREF = 2.5V
VS = 3V, 0V; VREF = 1.25V
l
l
l
60
–14
–1.5
60
16.8
7.3
V
V
V
P3/M3 Inputs
VS = ±15V; VREF = 0V
VS = 5V, 0V; VREF = 2.5V
VS = 3V, 0V; VREF = 1.25V
l
l
l
–15.2
0.5
0.95
15.2
4.2
1.95
V
V
V
P9/M9 Inputs
VS = ±15V; VREF = 0V
VS = 5V, 0V; VREF = 2.5V
VS = 3V, 0V; VREF = 1.25V
l
l
l
–15.2
0.85
1.0
15.2
3.9
1.9
V
V
V
VOS Op Amp Offset Voltage (Note 8) LT1991AMS, VS = 5V, 0V
l
15 50
135 µV
µV
LT1991AMS, VS = ±15V
l
15 80
160 µV
µV
LT1991MS
l
25 100
200 µV
µV
LT1991DD
l
25 150
250 µV
µV
∆VOS/∆T Op Amp Offset Voltage Drift (Note 6) l0.3 1 µV/°C
IB Op Amp Input Bias Current (Note 11)
l
2.5 5
7.5 nA
nA
IOS Op Amp Input Offset Current (Note 11) LT1991A
l
50 500
750 pA
pA
LT1991
l
50 1000
1500 pA
pA
Op Amp Input Noise Voltage 0.01Hz to 1Hz
0.01Hz to 1Hz
0.1Hz to 10Hz
0.1Hz to 10Hz
0.35
0.07
0.25
0.05
µVP-P
µVRMS
µVP-P
µVRMS
en Input Noise Voltage Density G = 1; f = 1kHz
G = 9; f = 1kHz 180
46 nV/√Hz
nV/√Hz
LT1991
LT1991
4
1991fh
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
RIN Input Impedance (Note 10) P1 (M1 = Ground)
P3 (M3 = Ground)
P9 (M9 = Ground)
l
l
l
630
420
350
900
600
500
1170
780
650
M1 (P1 = Ground)
M3 (P3 = Ground)
M9 (P9 = Ground)
l
l
l
315
105
35
450
150
50
585
195
65
∆R Resistor Matching (Note 9) 450k Resistors, LT1991A
Other Resistors, LT1991A
450k Resistors, LT1991
Other Resistors, LT1991
l
l
l
l
0.01
0.02
0.02
0.04
0.04
0.06
0.08
0.12
%
%
%
%
∆R/∆T Resistor Temperature Coefficient (Note 6) Resistor Matching
Absolute Value
l
l
0.3
–30 3 ppm/°C
ppm/°C
PSRR Power Supply Rejection Ratio VS = ±1.35V to ±18V (Note 8) l105 135 dB
Minimum Supply Voltage l2.4 2.7 V
VOUT Output Voltage Swing (to Either Rail) No Load
VS = 5V, 0V
VS = 5V, 0V
VS = ±15V
l
l
40
55
65
110
mV
mV
mV
1mA Load
VS = 5V, 0V
VS = 5V, 0V
VS = ±15V
l
l
150
225
275
300
mV
mV
mV
ISC Output Short-Circuit Current (Sourcing) Drive Output Positive;
Short Output to Ground
l
8
412 mA
mA
Output Short-Circuit Current (Sinking) Drive Output Negative;
Short Output to VS or Midsupply
l
8
421 mA
mA
BW –3dB Bandwidth G = 1
G = 3
G = 9
110
78
40
kHz
kHz
kHz
GBWP Op Amp Gain Bandwidth Product f = 10kHz 560 kHz
tr, tfRise Time, Fall Time G = 1; 0.1V Step; 10% to 90%
G = 9; 0.1V Step; 10% to 90% 3
8µs
µs
tsSettling Time to 0.01% G = 1; VS = 5V, 0V; 2V Step
G = 1; VS = 5V, 0V; –2V Step
G = 1; VS = ±15V, 10V Step
G = 1; VS = ±15V, –10V Step
42
48
114
74
µs
µs
µs
µs
SR Slew Rate VS = 5V, 0V; VOUT = 1V to 4V
VS = ±15V; VOUT = ±10V; VMEAS = ±5V
l
l
0.06
0.08 0.12
0.12 V/µs
V/µs
IsSupply Current VS = 5V, 0V
l
100 110
150 µA
µA
VS = ±15V
l
130 160
210 µA
µA
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.
LT1991 L7 LJUW 5
LT1991
5
1991fh
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
∆G Gain Error VS = ±15V, VOUT = ±10V; RL = 10k
G = 1
G = 3 or 9
l
l
±0.08
±0.12
%
%
GNL Gain Nonlinearity VS = ±15V; VOUT = ±10V; RL = 10k l1 10 ppm
∆G/∆T Gain Drift vs Temperature (Note 6) VS = ±15V; VOUT = ±10V; RL = 10k l0.3 3 ppm/°C
CMRR Common Mode Rejection Ratio,
Referred to Inputs (RTI)VS = ±15V; VCM = ±15.2V
G = 9
G = 3
G = 1
l
l
l
77
70
70
100
93
90
dB
dB
dB
VCM Input Voltage Range (Note 7) P1/M1 Inputs
VS = ±15V; VREF = 0V
VS = 5V, 0V; VREF = 2.5V
VS = 3V, 0V; VREF = 1.25V
l
l
l
–28
–0.5
0.75
27.6
5.1
2.35
V
V
V
P1/M1 Inputs, P9/M9 Connected to REF
VS = ±15V; VREF = 0V
VS = 5V, 0V; VREF = 2.5V
VS = 3V, 0V; VREF = 1.25V
l
l
l
60
–14
–1.5
60
16.8
7.3
V
V
V
P3/M3 Inputs
VS = ±15V; VREF = 0V
VS = 5V, 0V; VREF = 2.5V
VS = 3V, 0V; VREF = 1.25V
l
l
l
–15.2
0.5
0.95
15.2
4.2
1.95
V
V
V
P9/M9 Inputs
VS = ±15V; VREF = 0V
VS = 5V, 0V; VREF = 2.5V
VS = 3V, 0V; VREF = 1.25V
l
l
l
–15.2
0.85
1.0
15.2
3.9
1.9
V
V
V
VOS Op Amp Offset Voltage (Note 8) LT1991MS
l
25 100
285 µV
µV
LT1991DD
l
25 150
295 µV
µV
∆VOS/∆T Op Amp Offset Voltage Drift (Note 6) l0.3 1 µV/°C
IB Op Amp Input Bias Current (Note 11)
l
2.5 5
25 nA
nA
IOS Op Amp Input Offset Current (Note 11)
l
50 1000
4500 pA
pA
Op Amp Input Noise Voltage 0.01Hz to 1Hz
0.01Hz to 1Hz
0.1Hz to 10Hz
0.1Hz to 10Hz
0.35
0.07
0.25
0.05
µVP-P
µVRMS
µVP-P
µVRMS
en Input Noise Voltage Density G = 1; f = 1kHz
G = 9; f = 1kHz 180
46 nV/√Hz
nV/√Hz
RIN Input Impedance (Note 10) P1 (M1 = Ground)
P3 (M3 = Ground)
P9 (M9 = Ground)
l
l
l
630
420
350
900
600
500
1170
780
650
M1 (P1 = Ground)
M3 (P3 = Ground)
M9 (P9 = Ground)
l
l
l
315
105
35
450
150
50
585
195
65
∆R Resistor Matching (Note 9) 450k Resistors
Other Resistors
l
l
0.02
0.04 0.08
0.12 %
%
∆R/∆T Resistor Temperature Coefficient (Note 6) Resistor Matching
Absolute Value
l
l
0.3
–30 3 ppm/°C
ppm/°C
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.
LT1991
LT1991
6
1991fh
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
PSRR Power Supply Rejection Ratio VS = ±1.35V to ±18V (Note 8) l105 135 dB
Minimum Supply Voltage l2.4 2.7 V
VOUT Output Voltage Swing (to Either Rail) No Load
VS = 5V, 0V
VS = 5V, 0V
VS = ±15V
l
l
40
55
75
120
mV
mV
mV
1mA Load
VS = 5V, 0V
VS = 5V, 0V
VS = ±15V
l
l
150
225
300
340
mV
mV
mV
ISC Output Short-Circuit Current (Sourcing) Drive Output Positive;
Short Output to Ground
l
8
412 mA
mA
Output Short-Circuit Current (Sinking) Drive Output Negative;
Short Output to VS or Midsupply
l
8
421 mA
mA
BW –3dB Bandwidth G = 1
G = 3
G = 9
110
78
40
kHz
kHz
kHz
GBWP Op Amp Gain Bandwidth Product f = 10kHz 560 kHz
tr, tfRise Time, Fall Time G = 1; 0.1V Step; 10% to 90%
G = 9; 0.1V Step; 10% to 90% 3
8µs
µs
tsSettling Time to 0.01% G = 1; VS = 5V, 0V; 2V Step
G = 1; VS = 5V, 0V; –2V Step
G = 1; VS = ±15V, 10V Step
G = 1; VS = ±15V, –10V Step
42
48
114
74
µs
µs
µs
µs
SR Slew Rate VS = 5V, 0V; VOUT = 1V to 4V
VS = ±15V; VOUT = ±10V; VMEAS = ±5V
l
l
0.06
0.08 0.12
0.12 V/µs
V/µs
IsSupply Current VS = 5V, 0V
l
100 110
180 µA
µA
VS = ±15V
l
130 160
250 µA
µA
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.
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 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
are grounded and VS = ±15V (see Applications Information section about
“High Voltage CM Difference Amplifiers”).
Note 3: A heat sink may be required to keep the junction temperature
below absolute maximum ratings.
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 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 6: This parameter is not 100% tested.
Note 7: Input voltage range is guaranteed by the CMRR test at VS = ±15V.
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 8: Offset voltage, offset voltage drift and PSRR are defined as
referred to the internal op amp. You can calculate output offset as follows.
In the case of balanced source resistance, VOS,OUT = VOSNOISEGAIN
+ IOS • 450k + IB • 450k • (1– RP/RN) where RP and RN are the total
resistance at the op amp positive and negative terminal respectively.
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 10: Input impedance is tested by a combination of direct
measurements and correlation to the CMRR and gain error tests.
Note 11: IB and IOS are tested at VS = 5V, 0V only.
LT1991 TA = 35°C ; 25°C / \J \ /\ S‘NKI‘NG mm A vs: :ISV vow: :mv \ / 44* (mum; EDGE) / // sa' (mswe EDGE) L7 LJUW 7
LT1991
7
1991fh
SUPPLY VOLTAGE (±V)
0
SUPPLY CURRENT (µA)
200
175
150
125
100
75
50
25
016
1991 G01
42 6 10 14 18
812 20
TA = 85°C
TA = –40°C
TA = 25°C
TEMPERATURE (°C)
–50
OUTPUT VOLTAGE SWING (mV)
100
1991 G02
0 50
60
40
20
VEE –25 25 75 125
VS = 5V, 0V
NO LOAD
OUTPUT HIGH
(RIGHT AXIS)
OUTPUT LOW
(LEFT AXIS)
VCC
–20
–40
–60
LOAD CURRENT (mA)
0
OUTPUT VOLTAGE (mV)
1400
1200
1000
800
600
400
200
VEE
1991 G03
21098765
13 4
VS = 5V, 0V
TA = 85°C
TA = –40°C
TA = 25°C
LOAD CURRENT (mA)
VCC
–100
–200
–300
–400
–500
–600
–700
–800
–900
–1000
OUTPUT VOLTAGE SWING (mV)
1991 G04
0123456 7 8 9 10
VS = 5V, 0V
TA = 85°C
TA = –40°C
TA = 25°C
TEMPERATURE (°C)
–50
OUTPUT SHORT-CIRCUIT CURRENT (mA)
25
20
15
10
5
0050 75
1991 G05
–25 25 100 125
VS = 5V, 0V
SINKING
SOURCING
GAIN (V/V)
1
INPUT OFFSET VOLTAGE (µV)
150
100
50
0
–50
–100
–150 129 10 11 135
1991 G06
2 3 8764
VS = 5V, 0V
REPRESENTATIVE PARTS
GAIN (V/V)
1
OUTPUT OFFSET VOLTAGE (µV)
1000
750
500
250
0
–250
–500
–750
–1000 129 10 11 135
1991 G07
2 3 8764
VS = 5V, 0V
REPRESENTATIVE PARTS
LOAD CURRENT (mA)
0
GAIN ERROR (%)
35
1991 G08
1 2 4
0.04
0.03
0.02
0.01
0
–0.01
–0.02
–0.03
–0.04
GAIN = 1
VS = ±15V
VOUT = ±10V
TA = 25°C
REPRESENTATIVE UNITS
TEMPERATURE (°C)
–50
SLEW RATE (V/µs)
0.30
0.25
0.20
0.15
0.10
0.05
025 75
1991 G09
–25 0 50 100 125
GAIN = 1
VS = ±15V
VOUT = ±10V
SR (FALLING EDGE)
SR+ (RISING EDGE)
TYPICAL PERFORMANCE CHARACTERISTICS
Supply Current vs Supply Voltage
Output Voltage Swing
vs Temperature
Output Voltage Swing
vs Load Current (Output Low)
Output Voltage Swing
vs Load Current (Output High)
Output Short-Circuit Current
vs Temperature
Input Offset Voltage
vs Difference Gain
Output Offset Voltage
vs Difference Gain
Gain Error vs Load Current
Slew Rate vs Temperature
(Difference Amplifier Configuration)
LT1991
LT1991
8
1991fh
GAIN SETTING (V/V)
1
–3dB BANDWIDTH (kHz)
120
100
80
60
40
20
03 5 7 9
1991 G10
11 132 4 6 8 10 12
VS = 5V, 0V
TA = 25°C
Bandwidth vs Gain
CMRR vs Frequency
PSRR vs Frequency
Output Impedance vs Frequency
CMRR vs Temperature
Gain Error vs Temperature
Gain vs Frequency
Gain and Phase vs Frequency
0.01Hz to 1Hz Voltage Noise
(Difference Amplifier Configuration)
FREQUENCY (Hz)
CMRR (dB)
120
110
100
90
80
70
60
50
40
30
20
10
010 1k 10k 1M
1991 G11
100 100k
VS = 5V, 0V
TA = 25°C
GAIN = 9
GAIN = 1 GAIN = 3
PSRR (dB)
120
110
100
90
80
70
60
50
40
30
20
10
0
VS = 5V, 0V
TA = 25°C
GAIN = 9
GAIN = 1 GAIN = 3
FREQUENCY (Hz)
10 1k 10k
1991 G12
100 100k
FREQUENCY (Hz)
OUTPUT IMPEDANCE (Ω)
1 100 1k 100k10k
1991 G13
10
1000
100
10
1
0.1
0.01
VS = 5V, 0V
TA = 25°C
GAIN = 9
GAIN = 1
GAIN = 3
TEMPERATURE (°C)
–50
CMRR (dB)
120
100
80
60
40
20
025 75
1991 G14
–25 0 50 100 125
GAIN = 1
VS = ±15V
REPRESENTATIVE UNITS
TEMPERATURE (°C)
–50
GAIN ERROR (%)
0.030
0.025
0.020
0.015
0.010
0.005
025 75
1991 G15
–25 0 50 100 125
GAIN = 1
VS = ±15V
REPRESENTATIVE UNITS
FREQUENCY (kHz)
1
GAIN (dB)
30
20
10
0
–10
–20 10 100
600
1991 G16
GAIN = 9
GAIN = 3
GAIN = 1
VS = 5V, 0V
TA = 25°C
FREQUENCY (kHz)
1
GAIN (dB)
PHASE (deg)
2
1
0
–1
–2
–3
–4
–5
–6
–7
–8
0
–45
–90
–135
–180
10 100 400
1991 G17
0.5
VS = 5V, 0V
TA = 25°C
GAIN = 1
PHASE
GAIN
VS = ±15V
TA = 25°C
MEASURED IN G =13
REFERRED TO OP AMP INPUTS
0 10 20 30 40 50 60 70 80 90 100
TIME (s)
OP AMP VOLTAGE NOISE (100nV/DIV)
1991 G21
TYPICAL PERFORMANCE CHARACTERISTICS
LT1991 L7 LJUW 9
LT1991
9
1991fh
TYPICAL PERFORMANCE CHARACTERISTICS
P1 (Pin 1): Noninverting Gain-of-1 input. Connects a 450k
internal resistor to the op amp’s noninverting input.
P3 (Pin 2): Noninverting Gain-of-3 input. Connects a 150k
internal resistor to the op amp’s noninverting input.
P9 (Pin 3): Noninverting Gain-of-9 input. Connects a 50k
internal resistor to the op amp’s noninverting input.
VEE (Pin 4): Negative Power Supply. Can be either ground
(in single supply applications), or a negative voltage (in
split supply applications).
REF (Pin 5): Reference Input. Sets the output level when
difference between inputs is zero. Connects a 450k internal
resistor to the op amp’s noninverting input.
OUT (Pin 6): Output. VOUT = VREF + 1 • (VP1VM1) + 3 •
(VP3 – VM3) + 9 • (VP9 – VM9).
VCC (Pin 7): Positive Power Supply. Can be anything from
2.7V to 36V above the VEE voltage.
M9 (Pin 8): Inverting Gain-of-9 input. Connects a 50k
internal resistor to the op amp’s inverting input.
M3 (Pin 9): Inverting Gain-of-3 input. Connects a 150k
internal resistor to the op amp’s inverting input.
M1 (Pin 10): Inverting Gain-of-1 input. Connects a 450k
internal resistor to the op amp’s inverting input.
Exposed Pad: Must be soldered to PCB.
(Difference Amplifier Configuration)
50mV/DIV
5µs/DIV
GAIN = 1
1991 G18
50mV/DIV
5µs/DIV 1991 G19
GAIN = 3
50mV/DIV
5µs/DIV
GAIN = 9
1991 G20
Small Signal Transient Response
Small Signal Transient Response
Small Signal Transient Response
LT1991
1991 BD
9 8
2 3 4 5
7 610
1
M1 M3 M9
P1 P3 P9
VCC
VEE
OUT
REF
50k
50k
150k
150k
450k
450k
450k
450k
INM
INP
OUT
4pF
4pF
PIN FUNCTIONS
BLOCK DIAGRAM
LT1991
LT1991
10
1991fh
Introduction
The LT1991 may be the last op amp you ever have to stock.
Because it provides you with several precision matched
resistors, you can easily configure it into several different
classical gain circuits without adding external components.
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.
The Op Amp
The op amp internal to the LT1991 is a precision device
with 15µV typical offset voltage and 3nA input bias current.
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 VCC and 1V of
VEE. For many configurations though, the chip inputs will
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,
it is stable into capacitive loads up to 500pF. In noise gains
below 2, it is stable into capacitive loads up to 100pF.
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
therefore be taken beyond the supply voltages. The naming
of the pins “P1,” “P3,” “P9,” etc., is based on their relative
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.
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 LT1991 input noise is dominated by the Johnson
noise of the internal resistors (√4kTR). Paralleling all
four resistors to the +input gives a 32.1resistance,
for 23nV/√Hz of voltage noise. The equivalent network
on theinput gives another 23nV/√Hz , and taking their
RMS sum gives a total 33nV/√Hz input referred noise floor.
Output noise depends on configuration and noise gain.
Input Resistance
The LT1991 input resistances vary with configuration,
but once configured are apparent on inspection. Note that
resistors connected to the op amp’sinput are looking
into a virtual ground, so they simply parallel. Any feedback
resistance around the op amp 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 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.
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
APPLICATIONS INFORMATION
LT1991 H01 %%H3% 4:]:‘3 | L7 LJUW 1 1
LT1991
11
1991fh
The maximum voltage allowed on the P3, M3, P9, and
M9 inputs includes the positive and negative supply plus
a diode drop. These pins should not be driven more than
0.2V outside of the supply rails. This is because they are
connected through diodes to internal manufacturing post-
package trim circuitry, and through a substrate diode to
VEE. If more than 10mA is allowed to flow through these
pins, there is a risk that the LT1991 will be detrimmed or
damaged. The P1 and M1 inputs do not have clamp diodes
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.
The input voltage range of the internal op amp extends
to within 1.2V of VCC and 1V of VEE. The voltage at which
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.
For valid circuit function, the op amp output must not be
clipped. The output will clip if the input signals are attempt-
ing to force it to within 40mV of its supply voltages. This
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
as a gain of 13 difference amplifier on a single supply
with the output REF connected to ground. This is a great
circuit, but it does not support VDM = 0V at any common
mode because the output clips into ground while trying
to produce 0VOUT. It can be fixed simply by declaring the
valid input differential range not to extend below +4mV,
or by elevating the REF pin above 40mV, or by providing
a negative supply.
Calculating Input Voltage Range
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 RF and RG are
dictated by how the P inputs and REF pin are connected.
By superposition we can write:
VINT = VEXT • (RF/(RF + RG)) + VREF • (RG/(RF + RG))
Or, solving for VEXT:
VEXT = VINT • (1 + RG/RF) – VREFRG/RF
But valid VINT voltages are limited to VCC – 1.2V and VEE
+ 1V, so:
MAX VEXT = (VCC – 1.2) • (1 + RG/RF) – VREFRG/RF
and:
MIN VEXT = (VEE + 1) • (1 + RG/RF) – VREFRG/RF
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
the limit on this additional range, see Figure 3. Note that,
+
1991 F01
50k
150k
450k
50k
150k
450k
450k
450k REF
5V
VCM
2.5V
VDM
0V
+
8
7
6
5
4
9
10
1
2
3
LT1991
VOUT = 13 • VDM
4pF
4pF
+
VREF
RF
RF
RG
RG
1991 F02
VEXT VINT
VCC
VEE
Figure 1. Difference Amplifier Cannot Produce
0V on a Single Supply. Provide a Negative
Supply, or Raise Pin 5, or Provide 4mV of VDM
Figure 2. Calculating CM Input Voltage Range
APPLICATIONS INFORMATION
LT1991 N :D \ _ 2?,— Apr AH .—|r M— _W_.
LT1991
12
1991fh
with VMORE = 0, the op amp output is at VREF. From the
max VEXT (the high cm limit), as VMORE goes positive, the
op amp output will go more negative from VREF by the
amount VMORERF/RG, so:
VOUT = VREF – VMORERF/RG
Or:
VMORE = (VREF – VOUT) • RG/RF
The most negative that VOUT can go is VEE + 0.04V, so:
Max VMORE = (VREF – VEE – 0.04V) • RG/RF
(should be positive)
The situation where this function is negative, and there-
fore problematic, when VREF = 0 and VEE = 0, has already
been dealt with in Figure 1. The strength of the equation
is demonstrated in that it provides the three solutions
suggested in Figure 1: raise VREF, lower VEE, or provide
some negative VMORE.
Likewise, from the lower common mode extreme, mak-
ing the negative input more negative will raise the output
voltage, limited by VCC – 0.04V.
MIN VMORE = (VREF – VCC + 0.04V) • RG/RF
(should be negative)
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.
The Classical Noninverting Amplifier: High Input Z
Perhaps the most common op amp configuration is the
noninverting amplifier. Figure 4 shows the textbook
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
that gain and noise gain are identical, for optimal precision.
+
VREF
R
F
RF
RG
RG
1991 F03
VEXT
MAX OR MIN
VINT
VMORE
VCC
VEE
+
RF
RG
VIN
VIN
VOUT
VOUT
VOUT = GAIN • VIN
GAIN = 1 + RF/RG
+
1991 F04
50k
150k
450k
50k
150k
450k
450k
450k
8
6
5
9
10
1
2
3
LT1991
CLASSICAL NONINVERTING OP AMP CONFIGURATION.
YOU PROVIDE THE RESISTORS.
CLASSICAL NONINVERTING OP AMP CONFIGURATION
IMPLEMENTED WITH LT1991. RF = 225k, RG = 50k, GAIN = 5.5.
GAIN IS ACHIEVED BY GROUNDING, FLOATING OR FEEDING BACK
THE AVAILABLE RESISTORS TO ARRIVE AT DESIRED RF AND RG.
WE PROVIDE YOU WITH <0.1% RESISTORS.
4pF
4pF
Figure 3. Calculating Additional
Voltage Range of Inverting Inputs
Figure 4. The LT1991 as a Classical Noninverting Op Amp
APPLICATIONS INFORMATION
L7 LJUW LT1991 13
LT1991
13
1991fh
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 M9 M3 M1
1 Output Output Output
1.077 Output Output Ground
1.1 Output Float Ground
1.25 Float Output Ground
1.273 Output Ground Output
1.3 Output Ground Float
1.4 Output Ground Ground
2 Float Float Ground
2.5 Float Ground Output
2.8 Ground Output Output
3.25 Ground Output Float
3.5 Ground Output Ground
4 Float Ground Float
5 Float Ground Ground
5.5 Ground Float Output
7 Ground Ground Output
10 Ground Float Float
11 Ground Float Ground
13 Ground Ground Float
14 Ground Ground Ground
APPLICATIONS INFORMATION
LT1991 vs+ VS‘
LT1991
14
1991fh
VSVS
VS+
1991 F05
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VIN
VEE
VS+
VS
VS+
VS
VS+
VS
VS+
VS
VS+
VS
VS+
VS
VS+
VS
VS+
VS
VS+
VS
VS+
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VIN
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VIN
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VIN
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
VIN
VIN
VIN
OUT
VCC
VOUT
VIN
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VIN
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VIN
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VIN
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
GAIN = 1 GAIN = 2 GAIN = 3.25
GAIN = 4 GAIN = 5 GAIN = 5.5
GAIN = 7 GAIN = 10
GAIN = 13 GAIN = 14
GAIN = 11
Figure 5. Some Implementations of Classical Noninverting
Gains Using the LT1991. High Input Z Is Maintained
APPLICATIONS INFORMATION
L7 LJUW LT1991 15
LT1991
15
1991fh
VIN
OKAY UP
TO ±60V +
50k
150k
450k
450k
5
1
2
3
LT1991 ATTENUATING TO THE +INPUT BY
DRIVING AND GROUNDING AND FLOATING
INPUTS RA = 450k, RG = 50k, SO A = 0.1.
VINT
VINT
VINT = A • VIN
A = RG/(RA + RG)
VIN
LT1991
RA
RG
1991 F06
CLASSICAL ATTENUATOR
4pF
Attenuation Using the P Input Resistors
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.
Because the attenuations and the noninverting gains are set
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%.
Figure 6. LT1991 Provides for Easy Attenuation to the Op Amp’s
+Input. The P1 Input Can Be Taken Well Outside of the Supplies
Figure 7. Over 346 Unique Gain Settings Achievable with the
LT1991 by Combining Attenuation with Noninverting Gain
COUNT
0
100
10
1
0.1
0.01 150
1991 F07
50 100 200 250 350
300
GAIN
Table 2. Configuring the P Pins for Various Attenuations.
Those Shown in Bold Are Functional Even When the Input Drive
Exceeds the Supplies.
P9, P3, P1, REF Connection
A P9 P3 P1 REF
0.0714 Ground Ground Drive Ground
0.0769 Ground Ground Drive Float
0.0909 Ground Float Drive Ground
0.1 Ground Float Drive Float
0.143 Ground Ground Drive Drive
0.182 Ground Float Drive Drive
0.2 Float Ground Drive Ground
0.214 Ground Drive Ground Ground
0.231 Ground Drive Float Ground
0.25 Float Ground Drive Float
0.286 Ground Drive Drive Ground
0.308 Ground Drive Drive Float
0.357 Ground Drive Drive Drive
0.4 Float Ground Drive Drive
0.5 Float Float Drive Ground
0.6 Float Drive Ground Ground
0.643 Drive Ground Ground Ground
0.692 Drive Ground Float Ground
0.714 Drive Ground Drive Ground
0.75 Float Drive Float Ground
0.769 Drive Ground Drive Float
0.786 Drive Ground Drive Drive
0.8 Float Drive Drive Ground
0.818 Drive Float Ground Ground
0.857 Drive Drive Ground Ground
0.9 Drive Float Float Ground
0.909 Drive Float Drive Ground
0.923 Drive Drive Float Ground
0.929 Drive Drive Drive Ground
1 Drive Drive Drive Drive
APPLICATIONS INFORMATION
LT1991 4w
LT1991
16
1991fh
Inverting Configuration
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 VIN
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.
+
RF
RG
VIN
VIN
(DRIVE)
VOUT
VOUT
VOUT = GAIN • VIN
GAIN = – RF/RG
+
1991 F08
50k
150k
450k
50k
150k
450k
450k
450k
8
6
5
9
10
1
2
3
LT1991
CLASSICAL INVERTING OP AMP CONFIGURATION.
YOU PROVIDE THE RESISTORS.
CLASSICAL INVERTING OP AMP CONFIGURATION IMPLEMENTED
WITH LT1991. RF = 225k, RG = 50k, GAIN = –4.5.
GAIN IS ACHIEVED BY GROUNDING, FLOATING OR FEEDING BACK
THE AVAILABLE RESISTORS TO ARRIVE AT DESIRED RF AND RG.
WE PROVIDE YOU WITH <0.1% RESISTORS.
4pF
4pF
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
Table 3. Configuring the M Pins for Simple Inverting Gains
M9, M3, M1 Connection
Gain M9 M3 M1
–0.077 Output Output Drive
–0.1 Output Float Drive
–0.25 Float Output Drive
–0.273 Output Drive Output
–0.3 Output Drive Float
–0.4 Output Drive Drive
–1 Float Float Drive
–1.5 Float Drive Output
–1.8 Drive Output Output
–2.25 Drive Output Float
–2.5 Drive Output Drive
–3 Float Drive Float
–4 Float Drive Drive
–4.5 Drive Float Output
–6 Drive Drive Output
–9 Drive Float Float
–10 Drive Float Drive
–12 Drive Drive Float
–13 Drive Drive Drive
APPLICATIONS INFORMATION
LT1991 L7 LJUW 17
LT1991
17
1991fh
4
VS
4
VS
VS+
1991 F09
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VIN
VEE
VS
VS+
VS
VS+
VS+
VS
VS+
VS
VS+
VS
VS+
VS
VS+
VS
VS+
VS
VS+
VS
VS+
REF
LT1991
8
9
10
1
2
3
7
6
5
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VIN
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VIN
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VIN
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
VIN
VIN
VIN
OUT
VCC
VOUT
VIN
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VIN
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VIN
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VIN
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
GAIN = –0.25 GAIN = –1 GAIN = –2.25
GAIN = –3 GAIN = –4 GAIN = –4.5
GAIN = –6 GAIN = –9
GAIN = –12 GAIN = –13
GAIN = –10
Figure 9. It Is Simple to Get Precision Inverting Gains with the LT1991.
Input Impedance Varies from 45kΩ (Gain = –13) to 450kΩ (Gain = –1)
APPLICATIONS INFORMATION
LT1991
LT1991
18
1991fh
Difference Amplifiers
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.
+
RF
RG
RG
VIN+
VIN+
VIN
VIN
VOUT
VOUT
VOUT = GAIN • (VIN+ – VIN)
GAIN = RF/RG
+
50k
150k
450k
50k
150k
450k
450k
450k
8
6
5
9
10
1
2
3
LT1991
CLASSICAL DIFFERENCE AMPLIFIER USING THE LT1991
CLASSICAL DIFFERENCE AMPLIFIER IMPLEMENTED
WITH LT1991. RF = 450k, RG = 150k, GAIN = 3.
ADDING THE DASHED CONNECTIONS CONNECTS THE
TWO 450k RESISTORS IN PARALLEL, SO RF IS REDUCED
TO 225k. GAIN BECOMES 225k/150k = 1.5.
RF
PARALLEL
TO CHANGE
RF, RG
M9
M3
M1
P1
P3
P9
4pF
4pF
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
Table 4. Connections Giving Difference Gains for the LT1991
Gain VIN+VINOutput GND (REF)
0.077 P1 M1 M3, M9 P3, P9
0.1 P1 M1 M9 P9
0.25 P1 M1 M3 P3
0.273 P3 M3 M1, M9 P1, P9
0.3 P3 M3 M9 P9
0.4 P1, P3 M1, M3 M9 P9
1P1 M1
1.5 P3 M3 M1 P1
1.8 P9 M9 M1, M3 P1, P3
2.25 P9 M9 M3 P3
2.5 P1, P9 M1, M9 M3 P3
3 P3 M3
4 P1, P3 M1, M3
4.5 P9 M9 M1 P1
6 P3, P9 M3, M9 M1 P1
9 P9 M9
10 P1, P9 M1, M9
12 P3, P9 M3, M9
13 P1, P3, P9 M1, M3, M9
APPLICATIONS INFORMATION
L7 LJUW |+‘| |'+| LT1991 Vs‘ v5+ 19
LT1991
19
1991fh
Figure 11. Many Difference Gains Are Achievable Just by Strapping the Pins
VS
VS+
1991 F11
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
VS
VS+
VS
VS+
VS
VS+
VS
VS+
VS
VS+
VS
VS+
VS
VS+
VS
VS+
VS
VS+
VS
VS+
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
GAIN = 0.25 GAIN = 1 GAIN = 2.25
GAIN = 3 GAIN = 4 GAIN = 4.5
GAIN = 6 GAIN = 9
GAIN = 12 GAIN = 13
GAIN = 10
VIN+
VIN
VIN+
VIN+
VIN+
VIN
VIN+
VIN
VIN+
VIN
VIN+
VIN
VIN+
VIN
VIN+
VIN
VIN+
VIN
VIN+
VIN
VIN
VIN
APPLICATIONS INFORMATION
LT1991 V»— N M I I K I I M ‘ ‘. I N u u n —w I I v —— ,' Apr ¢ _,w\,_—L M— N J_ V5 V5 V5 Vs Vs Vs vs vs vs, Vs 20 L7ELUEN2
LT1991
20
1991fh
1991 F13
VS
VS+
VS
VS+
VS
VS+
VS
VS+
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
GAIN = 2 GAIN = 5
GAIN = 7 GAIN = 8
GAIN = 11
VIN+
VIN
VIN+
VIN
VIN+
VIN
VIN+
VIN
VS
VS+
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VIN+
VIN
+
RF
RG
RG
VIN+VIN+
VIN
VIN
VOUT
VOUT
VOUT = GAIN • (VIN+ – VIN)
GAIN = RF/RG
+
1991 F12
50k
150k
450k
50k
150k
450k
450k
450k
8
6
5
9
10
1
2
3
LT1991
CLASSICAL DIFFERENCE AMPLIFIER
CLASSICAL DIFFERENCE AMPLIFIER IMPLEMENTED
WITH LT1991. RF = 450k, RG = 150k, GAIN = 3.
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
VIN+ VOLTAGE. CONNECTING P3 AND M1 GIVES +3 –1 = 2.
CONNECTIONS TO VIN ARE SYMMETRIC: M3 AND P1.
RF
CROSS-
COUPLING
M9
M3
M1
P1
P3
P9
4pF
4pF
Difference Amplifier: Additional Integer Gains Using
Cross-Coupling
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
ascross-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. Note that the equations can be written by inspection
from the VIN+ connections, and that the VIN connections
are simply the opposite (swap P for M and M for P). Noise
gain, bandwidth, and input impedance specifications for the
various cases are also tabulated, as these are not obvious.
Schematics are provided in Figure 13.
Figure 13. Integer Gain Difference
Amplifiers Using Cross-Coupling
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
Table 5. Connections Using Cross-Coupling. Note That Equations Can
Be Written by Inspection of the VIN+ Column
Gain
VIN+
VIN
Equation
Noise
Gain
–3dB BW
kHz
RIN+
Typ
RIN
Typ
2 P3, M1 M3, P1 3 – 1 5 70 281 141
5 P9, M3, M1 M9, P3, P1 9 – 3 – 1 14 32 97 49
6* P9, M3 M9, P3 9 – 3 13 35 122 49
7 P9, P1, M3 M9, M1, P3 9 + 1 – 3 14 32 121 44
8 P9, M1 M9, P1 9 – 1 11 38 248 50
11 P9, P3, M1 M9, M3, P1 9 + 3 – 1 14 32 242 37
*Gain of 6 is better implemented as shown previously, but is included here for completeness.
APPLICATIONS INFORMATION
LT1991 21 L7 LJUW
LT1991
21
1991fh
High Voltage CM Difference Amplifiers
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
that resistors RT attenuate the common mode voltage seen
by the op amp inputs. For the LT1991, the most useful
resistors for RG are the M1 and P1 450resistors, be-
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
the voltage at the op amp +input, VINT. By superposition
we can write:
VINT = VEXT • (RF||RT)/(RG + RF||RT) + VREF • (RG||RT)/
(RF + RG||RT) + VTERM • (RF||RG)/(RT + RF||RG)
Solving for VEXT:
VEXT = (1 + RG/(RF||RT)) • (VINT – VREF • (RG||RT)/
(RF + RG||RT) – VTERM • (RF||RG)/(RT + RF||RG))
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
VCC – 1.2 and VEE + 1 for VLIM will give the valid upper
and lower common mode extremes respectively. 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:
MAX VEXT = 11 • (VCC – 1.2V) – VREF – 9 • VTERM
= 11 • (10.8V) – 2.5 – 9 • 12 = 8.3V
and:
MIN VEXT = 11 • (VEE + 1V) – VREF – 9 • VTERM
= 11 • (1V) – 2.5 – 9 • 12 = –99.5V
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
circuits are shown in Figures 15, 16, 17 for various supplies.
+
RF
RG
RG
VIN+
(= VEXT)
VIN+
VIN
VIN
VOUT
VOUT
VOUT = GAIN • (VIN+ – VIN)
GAIN = RF/RG
+
1991 F14
50k
150k
450k
50k
150k
450k
450k
450k
8
7
4
6
5
9
10
1
2
3
LT1991
REF
HIGH CM VOLTAGE DIFFERENCE AMPLIFIER
INPUT CM TO OP AMP IS ATTENUATED BY
RESISTORS RT CONNECTED TO VTERM.
HIGH NEGATIVE CM VOLTAGE DIFFERENCE AMPLIFIER
IMPLEMENTED WITH LT1991.
RF = 450k, RG = 450k, RT 50k, GAIN = 1
VTERM = VCC = 12V, VREF = 2.5V, VEE = GROUND.
RF
M9
M3
M1
P1
P3
P9
VCC
VEE
RT
RT
VTERM
VREF
INPUT CM RANGE
= –60V TO 8.3V
12V
2.5V
4pF
4pF
Table 6. HighV CM Connections Giving Difference Gains for
the LT1991
Gain
VIN+
VIN
RT
Noise
Gain
Max, Min VEXT
(Substitute VCC – 1.2,
VEE + 1 for VLIM)
1 P1 M1 2 2 • VLIM - VREF
1 P1 M1 P3, M3 5 5 • VLIM – VREF – 3 • VTERM
1 P1 M1 P9, M9 11 11 • VLIM – VREF – 9 • VTERM
1 P1 M1 P3||P9
M3||M9
14 14 • VLIM – VREF – 12 • VTERM
Figure 14. Extending CM Input Range
APPLICATIONS INFORMATION
>>>> >>>> >>>> LT1991 :I L7LJCUEN2 22
LT1991
22
1991fh
Figure 15. Common Mode Ranges for Various LT1991 Configurations on VS = 3V, 0V; with Gain = 1
3V
1991 F15
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VIN
VIN+
VIN
VIN+
VIN
VIN+
VIN
VIN+
VEE
3V
3V
3V 3V
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = 0.8V TO 2.35V
VCM = 0V TO 4V
VCM = 2V TO 3.6V
VDM > 40mV
VCM = –1V TO 0.6V
VDM <–40mV
1.25V
1.25V
1.25V
1.25V
VIN
VIN+
3V
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = 3.8V TO 7.75V
1.25V
VIN
VIN+
3V
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = –1.5V TO 7.2V
1.25V
VIN
VIN+
3V
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = 9.8V TO 18.55V
1.25V
VIN
VIN+
3V 3V
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = –17.2V TO –8.45V
1.25V
1.25V
VIN
VIN+
3V
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = –2.25V TO 8.95V
1.25V
VIN
VIN+
3V
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = 12.75V TO 23.95V
1.25V
VIN
VIN+
3V 3V
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = –23.2V TO –12V
1.25V
VIN
VIN+
3V
3V
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = –5V TO –1.25V
1.25V
APPLICATIONS INFORMATION
LT1991 H II "II II IT IT L7HEJWEGR 23
LT1991
23
1991fh
Figure 16. Common Mode Ranges for Various LT1991 Configurations on VS = 5V, 0V; with Gain = 1
43V
1991 F16
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VIN
VIN+
VIN
VIN+
VIN
VIN+
VIN
VIN+
VEE
5V
5V
5V 5V
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = –0.5V TO 5.1V
VCM = –5V TO 9V
VCM = 2V TO 7.6V
VDM > 40mV
VCM = –3V TO 2.6V
VDM <–40mV
2.5V
2.5V
2.5V
2.5V
VIN
VIN+
5V
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = 2.5V TO 16.5V
2.5V
VIN
VIN+
5V
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = –14V TO 16.8V
2.5V
VIN
VIN+
5V
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = 8.5V TO 39.3V
2.5V
VIN
VIN+
5V 5V
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = –36.5V TO –5.7V
2.5V
2.5V
VIN
VIN+
5V
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = –18.5V TO 20.7V
2.5V
VIN
VIN+
5V
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = 11.5V TO 50.7V
2.5V
VIN
VIN+
5V 5V
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = –48.5V TO –9.3V
2.5V
VIN
VIN+
5V
5V
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = –12.5V TO 1.5V
2.5V
APPLICATIONS INFORMATION
LT1991 5v 5v 75v 5v 75v 5v 75v 5v 5v 75v 5v 75v : 5v 75v 5v 5v 75v _ _ : 5v 75v _ _ : "__ L7LJCUEN2 24
LT1991
24
1991fh
Figure 17. Common Mode Ranges for Various LT1991 Configurations on VS = ±5V, with Gain = 1
1991 F17
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VIN
VIN+
VIN
VIN+
VIN
VIN+
VIN
VIN+
VEE
5V
5V
5V 5V
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = –8V TO 7.6V
VCM = –20V TO 19V
VCM = –3V TO 12.6V
VDM > 40mV
VCM = –13V TO 2.6V
VDM <–40mV
–5V
–5V –5V
–5V –5V
–5V
–5V
–5V
–5V –5V
–5V
–5V
VIN
VIN+
5V
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = –5V TO 34V
VIN
VIN+
5V
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = –44V TO 41.8V
VIN
VIN+
5V
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = 1V TO 60V
–5V –5V
5V –5V
–5V
VIN
VIN+
5V 5V
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = –60V TO –3.2V
VIN
VIN+
5V
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = –56V TO 53.2V
VIN
VIN+
5V
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = 4V TO 60V
VIN
VIN+
5V 5V
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = –60V TO –6.8V
VIN
VIN+
5V
5V
M9
M3
M1
P1
P3
P9
OUT
VCC
VOUT
VEE
REF
LT1991
8
9
10
1
2
3
7
6
5
4
VCM = –35V TO 4V
APPLICATIONS INFORMATION
LT1991 %\/=% L7HEJWEGR 25
LT1991
25
1991fh
TYPICAL APPLICATIONS
+
+
VM
VP
VOUT
LT1991
1991 TA02
9 8
2 3 4 5
7610
1
+
1/2 LT6011
1/2 LT6011
4pF
4pF
Micropower AV = 10 Instrumentation Amplifier
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
3.00 ±0.10
(4 SIDES)
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
0.40 ± 0.10
BOTTOM VIEW—EXPOSED PAD
1.65 ± 0.10
(2 SIDES)
0.75 ±0.05
R = 0.125
TYP
2.38 ±0.10
(2 SIDES)
15
106
PIN 1
TOP MARK
(SEE NOTE 6)
0.200 REF
0.00 – 0.05
(DD) DFN REV C 0310
0.25 ± 0.05
2.38 ±0.05
(2 SIDES)
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
1.65 ±0.05
(2 SIDES)2.15 ±0.05
0.50
BSC
0.70 ±0.05
3.55 ±0.05 PACKAGE
OUTLINE
0.25 ± 0.05
0.50 BSC
DD Package
10-Lead Plastic DFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1699 Rev C)
PIN 1 NOTCH
R = 0.20 OR
0.35 × 45°
CHAMFER
LT1991 was 0‘27 (:uas nuts) [I I] D I] I]; (5252] 320 345 (‘25; ‘35 macPPDW (mm mm) (m?) ¢ ¢ Em Em 3:13“ L7LJCUEN2
LT1991
26
1991fh
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
MSOP (MS) 0307 REV E
0.53 ±0.152
(.021 ±.006)
SEATING
PLANE
0.18
(.007)
1.10
(.043)
MAX
0.17 –0.27
(.007 – .011)
TYP
0.86
(.034)
REF
0.50
(.0197)
BSC
1234 5
4.90 ±0.152
(.193 ±.006)
0.497 ±0.076
(.0196 ±.003)
REF
8910 76
3.00 ±0.102
(.118 ±.004)
(NOTE 3)
3.00 ±0.102
(.118 ±.004)
(NOTE 4)
NOTE:
1. DIMENSIONS IN MILLIMETER/(INCH)
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
0.254
(.010) 0° – 6° TYP
DETAIL “A”
DETAIL “A”
GAUGE PLANE
5.23
(.206)
MIN
3.20 – 3.45
(.126 – .136)
0.889 ±0.127
(.035 ±.005)
RECOMMENDED SOLDER PAD LAYOUT
0.305 ±0.038
(.0120 ±.0015)
TYP
0.50
(.0197)
BSC
0.1016 ±0.0508
(.004 ±.002)
MS Package
10-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1661 Rev E)
LT1991 L7 LJUW 27
LT1991
27
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.
REVISION HISTORY
REV DATE DESCRIPTION PAGE NUMBER
H 5/12 Corrected specified temperature range for C-grade parts in the Order Information table.
Corrected VCM = –20V to 19V and VCM = –5V to 34V configurations in Figure 17.
Updated Related Parts Table
2
24
28
(Revision history begins at Rev H)
LT1991 Vs=27vmzsv M. if fl'fifl 5v _:q ‘3
LT1991
28
1991fh
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 l FAX: (408) 434-0507 l www.linear.com
LINEAR TECHNOLOGY CORPORATION 2006
LT 0512 REV H • PRINTED IN USA
TYPICAL APPLICATION
PART NUMBER DESCRIPTION COMMENTS
LT1990 High Voltage, Gain Selectable Difference Amplifier ±250V Common Mode, Micropower, Pin Selectable Gain = 1, 10
LT1996 Precision Gain Selectable Difference Amplifier Micropower, Pin Selectable Up to Gain = 118
LT1995 High Speed, Gain Selectable Difference Amplifier 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 AV ≥ 5 Version of LT1991 Type Op Amp
LTC6910-X Programmable Gain Amplifiers 3 Gain Configurations, Rail-to-Rail Input and Output
LT1999 High Voltage Bidirectional Current Sense Amplifier CMRR > 80dB at 100kHz
LT5400 Quad Matched Resistor Network 0.01% Matching, CMRR > 86dB
VIN
VIN+
VIN
VCC
VS = 2.7V TO 36V
VS+
VS
M9
M3
M1
P1
P3
P9
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
V
OUT
LT1991
8
9
10
1
2
3
7
6
5
4
GAIN = 12
BW = 7Hz TO 32kHz
R2*
10k
R1
10k
VIN+ – VIN
10kΩ
ILOAD =
*SHORT R2 FOR LOWEST OUTPUT
OFFSET CURRENT. INCLUDE R2 FOR
HIGHEST OUTPUT IMPEDANCE.
0.1µF
F
1991 TA03
Bidirectional Current Source Single Supply AC Coupled Amplifier
VIN
= 14V to 53V
± 10VIN
5V
5V
M9
M3
M1
P1
P3
P9
VOUT =
LT1991
8
9
10
1
2
3
7
6
5
4
M9
M3
M1
P1
P3
P9
0-4VOUT
LT1991
REF
REF
8
9
10
1
2
3
7
6
5
–5V
5V
4
1
4
LT1790 –2.5
VIN
13
F
1991 TA04
2
6
Ultra-Stable Precision Attenuator Analog Level Adaptor
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