LMP7731
www.ti.com
SNOSAT6E – JULY 2007 – REVISED MARCH 2013
2.9 nV/sqrt(Hz) Low Noise, Precision, RRIO Amplifier
Check for Samples: LMP7731
FEATURES
DESCRIPTION
1
(Typical Values, TA = 25°C, VS = 5V)
23
•
•
•
•
•
•
•
•
•
•
•
Input Voltage Noise
– f = 3 Hz 3.3 nV/√Hz
– f = 1 kHz 2.9 nV/√Hz
CMRR 130 dB
Open Loop Gain 130 dB
GBW 22 MHz
Slew Rate 2.4 V/µs
THD @ f = 10 kHz, AV = +1, RL = 2 kΩ 0.001%
Supply Current per Channel 2.2 mA
Supply Voltage Range 1.8V to 5.5V
Operating Temperature Range −40°C to 125°C
Input Bias Current ±1.5 nA
RRIO
This operational amplifier offers low voltage noise of
2.9 nV/√Hz with a 1/f corner of only 3 Hz. The
LMP7731 has bipolar input stages with a bias current
of only 1.5 nA. This low input bias current,
complemented by the very low level of voltage noise,
makes the LMP7731 an excellent choice for
photometry applications.
The LMP7731 provides a wide GBW of 22 MHz while
consuming only 2 mA of current. This high gain
bandwidth along with the high open loop gain of 130
dB enables accurate signal conditioning in
applications with high closed loop gain requirements.
The LMP7731 has a supply voltage range of 1.8V to
5.5V, making it an ideal choice for battery operated
portable applications.
APPLICATIONS
•
•
•
The LMP7731 is a single, low noise, rail-to-rail input
and output, low voltage amplifier. The LMP7731 is
part of the LMP™ precision amplifier family and is
ideal for precision and low noise applications with low
voltage requirements.
Gas Analysis Instruments
Photometric Instrumentation
Medical Instrumentation
The LMP7731 is offered in the space saving 5-Pin
SOT-23 and 8-Pin SOIC packages.
Typical Performance Characteristics
Input Voltage Noise
vs.
Frequency
Input Current Noise
vs.
Frequency
100
100
10
VS = 2.5V, 3.3V, 5V
CURRENT NOISE (pA/ Hz)
VOLTAGE NOISE (nV/ Hz)
VS = 2.5V, 3.3V, 5V
VCM = 0.5V
VCM = 2.5V
VCM = 0.5V
10
VCM = 2.5V
1
0.1
1
10
100
1k
10k
1
0.1
1
10
100
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 1.
Figure 2.
1k
10k
1
2
3
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
LMP is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2007–2013, Texas Instruments Incorporated
LMP7731
SNOSAT6E – JULY 2007 – REVISED MARCH 2013
www.ti.com
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
Absolute Maximum Ratings
ESD Tolerance
(3)
(1) (2)
Human Body Model
Inputs pins only
2000V
All other pins
2000V
Machine Model
200V
Charge Device Model
1000V
VIN Differential
±2V
Supply Voltage (VS = V+ – V−)
6.0V
−65°C to 150°C
Storage Temperature Range
Junction Temperature
(4)
+150°C max
Soldering Information
(1)
(2)
(3)
(4)
Infrared or Convection (20 sec)
235°C
Wave Soldering Lead Temp. (10 sec)
260°C
Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is intended to be functional, but specific performance is not ensured. For ensured specifications and the test
conditions, see the Electrical Characteristics Tables.
If Military/Aerospace specified devices are required, please contact the TI Sales Office/ Distributors for availability and specifications.
Human Body Model, applicable std. MIL-STD-883, Method 3015.7. Machine Model, applicable std. JESD22-A115-A (ESD MM std. of
JEDEC)Field-Induced Charge-Device Model, applicable std. JESD22-C101-C (ESD FICDM std. of JEDEC).
The maximum power dissipation is a function of TJ(MAX), θJA. The maximum allowable power dissipation at any ambient temperature is
PD = (TJ(MAX) – TA)/ θJA. All numbers apply for packages soldered directly onto a PC Board.
Operating Ratings
(1)
−40°C to 125°C
Temperature Range
+
–
Supply Voltage (VS = V – V )
Package Thermal Resistance (θJA)
(1)
1.8V to 5.5V
5-Pin SOT-23
265°C/W
8-Pin SOIC
190°C/W
Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is intended to be functional, but specific performance is not ensured. For ensured specifications and the test
conditions, see the Electrical Characteristics Tables.
2.5V Electrical Characteristics
(1)
Unless otherwise specified, all limits are ensured for TA = 25°C, V+ = 2.5V, V− = 0V, VCM = V+/2, RL >10 kΩ to V+/2. Boldface
limits apply at the temperature extremes.
Parameter
Input Offset Voltage
VOS
(1)
(2)
(3)
(4)
2
Min
(2)
Typ
(3)
Input Offset Voltage Temperature
Drift
Max
(2)
VCM = 2.0V
±9
±500
±600
VCM = 0.5V
±9
±500
±600
VCM = 2.0V
±0.5
±5.5
VCM = 0.5V
±0.2
±5.5
VCM = 2.0V
±1
±30
±45
VCM = 0.5V
±12
±50
±75
(4)
TCVOS
IB
Test Conditions
Input Bias Current
Units
μV
μV/°C
nA
Electrical Table values apply only for factory testing conditions at the temperature indicated. Factory testing conditions result in very
limited self-heating of the device such that TJ = TA. No specification of parametric performance is indicated in the electrical tables under
conditions of internal self-heating where TJ > TA. Absolute maximum Ratings indicate junction temperature limits beyond which the
device maybe permanently degraded, either mechanically or electrically.
All limits are specified by testing, statistical analysis or design.
Typical values represent the most likely parametric norm as determined at the time of characterization. Actual typical values may vary
over time and will also depend on the application and configuration. The typical values are not tested and are not ensured on shipped
production material.
Ambient production test is performed at 25°C with a variance of ±3°C.
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2.5V Electrical Characteristics (1) (continued)
Unless otherwise specified, all limits are ensured for TA = 25°C, V+ = 2.5V, V− = 0V, VCM = V+/2, RL >10 kΩ to V+/2. Boldface
limits apply at the temperature extremes.
Parameter
IOS
TCIOS
CMRR
PSRR
Test Conditions
Min
(2)
AVOL
(3)
Common Mode Rejection Ratio
Power Supply Rejection Ratio
Common Mode Voltage Range
Open Loop Voltage Gain
±1
VCM = 0.5V
±11
±60
±80
VCM = 0.5V and VCM = 2.0V
0.0474
0.15V ≤ VCM ≤ 0.7V
0.23V ≤ VCM ≤ 0.7V
101
89
120
1.5V ≤ VCM ≤ 2.35V
1.5V ≤ VCM ≤ 2.27V
105
99
129
2.5V ≤ V+ ≤ 5V
111
105
129
Large Signal CMRR ≥ 80 dB
0
112
104
130
RL = 2 kΩ to V+/2
VOUT = 0.5V to 2.0V
109
90
119
dB
V
dB
RL = 10 kΩ to V+/2
4
50
75
RL = 2 kΩ to V+/2
13
50
75
RL = 10 kΩ to V /2
6
50
75
RL = 2 kΩ to V+/2
9
50
75
Output Voltage Swing Low
IS
nA/°C
2.5
RL = 10 kΩ to V+/2
VOUT = 0.5V to 2.0V
+
Supply Current
(Per Channel)
nA
117
VOUT
Output Current
Units
dB
Output Voltage Swing High
IOUT
(2)
VCM = 2.0V
Input Offset Current
Input Offset Current Drift
Max
±50
±75
1.8V ≤ V+ ≤ 5.5V
CMVR
Typ
Sourcing, VOUT = V+/2
VIN (diff) = 100 mV
22
12
31
Sinking, VOUT = V+/2
VIN (diff) = −100 mV
15
10
44
mV from
either rail
mA
VCM = 2.0V
2.0
2.7
3.4
VCM = 0.5V
2.3
3.1
3.9
mA
SR
Slew Rate
AV = +1, CL = 10 pF, RL = 10 kΩ to
V+/2,
VO = 2 VPP
2.4
V/μs
GBW
Gain Bandwidth
CL = 20 pF, RL = 10 kΩ to V+/2
21
MHz
+
GM
Gain Margin
CL = 20 pF, RL = 10 kΩ to V /2
14
dB
ΦM
Phase Margin
CL = 20 pF, RL = 10 kΩ to V+/2
60
deg
RIN
Input Resistance
THD+N
Total Harmonic Distortion + Noise
AV = 1, f = 1 kHz, Amplitude = 1V
Input Referred Voltage Noise
Density
f = 1 kHz, VCM = 2.0V
3
f = 1 kHz, VCM = 0.5V
3
Input Voltage Noise
0.1 Hz to 10 Hz
75
Input Referred Current Noise
Density
f = 1 kHz, VCM = 2.0V
1.1
f = 1 kHz, VCM = 0.5V
2.3
en
in
Differential Mode
38
kΩ
Common Mode
151
MΩ
0.002
%
nV/√Hz
nVPP
pA/√Hz
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3.3V Electrical Characteristics
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(1)
Unless otherwise specified, all limits are ensured for TA = 25°C, V+ = 3.3V, V− = 0V, VCM = V+/2, RL > 10 kΩ to V+/2. Boldface
limits apply at the temperature extremes.
Parameter
Input Offset Voltage
VOS
Test Conditions
Min
(2)
Typ
(3)
IB
Input Offset Voltage Temperature
Drift
VCM = 2.5V
±6
VCM = 0.5V
±6
±500
±600
VCM = 2.5V
±0.5
±5.5
VCM = 0.5V
±0.2
±5.5
VCM = 2.5V
±1.5
±30
±45
VCM = 0.5V
±13
±50
±77
VCM = 2.5V
±1
±50
±70
VCM = 0.5V
±11
±60
±80
Input Bias Current
IOS
Input Offset Current
TCIOS
CMRR
PSRR
Input Offset Current Drift
Common Mode Rejection Ratio
Power Supply Rejection Ratio
VCM = 0.5V and VCM = 2.5V
0.048
0.15V ≤ VCM ≤ 0.7V
0.23V ≤ VCM ≤ 0.7V
101
89
120
1.5V ≤ VCM ≤ 3.15V
1.5V ≤ VCM ≤ 3.07V
105
99
130
2.5V ≤ V+ ≤ 5.0V
111
105
129
+
1.8V ≤ V ≤ 5.5V
CMVR
Common Mode Voltage Range
Large Signal CMRR ≥ 80 dB
+
AVOL
Open Loop Voltage Gain
RL = 10 kΩ to V /2
VOUT = 0.5V to 2.8V
+
RL = 2 kΩ to V /2
VOUT = 0.5V to 2.8V
0
130
110
92
119
SR
(1)
(2)
(3)
(4)
4
Slew Rate
nA
nA
dB
V
dB
RL = 10 kΩ to V+/2
5
50
75
RL = 2 kΩ to V+/2
14
50
75
RL = 10 kΩ to V /2
9
50
75
RL = 2 kΩ to V+/2
13
50
75
Output Voltage Swing Low
IS
μV/°C
nA/°C
3.3
112
104
+
Supply Current
(Per Channel)
μV
117
VOUT
Output Current
Units
dB
Output Voltage Swing High
IOUT
(2)
±500
±600
(4)
TCVOS
Max
Sourcing, VOUT = V+/2
VIN (diff) = 100 mV
28
22
45
Sinking, VOUT = V+/2
VIN (diff) = -100 mV
25
20
48
mV from
either rail
mA
VCM = 2.5V
2.1
2.8
3.5
VCM = 0.5V
2.4
3.2
4.0
AV = +1, CL = 10 pF, RL = 10 kΩ to
V+/2,
VOUT = 2 VPP
2.4
mA
V/μs
Electrical Table values apply only for factory testing conditions at the temperature indicated. Factory testing conditions result in very
limited self-heating of the device such that TJ = TA. No specification of parametric performance is indicated in the electrical tables under
conditions of internal self-heating where TJ > TA. Absolute maximum Ratings indicate junction temperature limits beyond which the
device maybe permanently degraded, either mechanically or electrically.
All limits are specified by testing, statistical analysis or design.
Typical values represent the most likely parametric norm as determined at the time of characterization. Actual typical values may vary
over time and will also depend on the application and configuration. The typical values are not tested and are not ensured on shipped
production material.
Ambient production test is performed at 25°C with a variance of ±3°C.
Submit Documentation Feedback
Copyright © 2007–2013, Texas Instruments Incorporated
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LMP7731
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SNOSAT6E – JULY 2007 – REVISED MARCH 2013
3.3V Electrical Characteristics (1) (continued)
Unless otherwise specified, all limits are ensured for TA = 25°C, V+ = 3.3V, V− = 0V, VCM = V+/2, RL > 10 kΩ to V+/2. Boldface
limits apply at the temperature extremes.
Parameter
GBW
Test Conditions
Gain Bandwidth
Min
(2)
Typ
+
22
+
CL = 20 pF, RL = 10 kΩ to V /2
(3)
Max
(2)
Units
MHz
GM
Gain Margin
CL = 20 pF, RL = 10 kΩ to V /2
14
dB
ΦM
Phase Margin
CL = 20 pF, RL = 10 kΩ to V+/2
62
deg
RIN
Input Resistance
THD+N
Total Harmonic Distortion + Noise
AV = 1, f = 1 kHz, Amplitude = 1V,
Input Referred Voltage Noise
Density
f = 1 kHz, VCM = 2.5V
2.9
f = 1 kHz, VCM = 0.5V
2.9
Input Voltage Noise
0.1 Hz to 10 Hz
65
Input Referred Current Noise
Density
f = 1 kHz, VCM = 2.5V
1.1
f = 1 kHz, VCM = 0.5V
2.1
en
in
5V Electrical Characteristics
Differential Mode
38
kΩ
Common Mode
151
MΩ
0.002
%
nV/√Hz
nVPP
pA/√Hz
(1)
Unless otherwise specified, all limits are ensured for TA = 25°C, V+ = 5V, V− = 0V, VCM = V+/2, RL > 10 kΩ to V+/2. Boldface
limits apply at the temperature extremes.
Parameter
Input Offset Voltage
VOS
Test Conditions
Min
(2)
IB
Input Offset Voltage Temperature
Drift
CMRR
PSRR
Input Offset Current Drift
Common Mode Rejection Ratio
Power Supply Rejection Ratio
±6
VCM = 0.5V
±6
±500
±600
VCM = 4.5V
±0.5
±5.5
VCM = 0.5V
±0.2
±5.5
VCM = 4.5V
±1.5
±30
±50
VCM = 0.5V
±14
±50
±85
VCM = 4.5V
±1
±50
±70
VCM = 0.5V
±11
±65
±80
VCM = 0.5V and VCM = 4.5V
0.0482
0.15V ≤ VCM ≤ 0.7V
0.23V ≤ VCM ≤ 0.7V
101
89
120
1.5V ≤ VCM ≤ 4.85V
1.5V ≤ VCM ≤ 4.77V
105
99
130
2.5V ≤ V+ ≤ 5V
111
105
129
1.8V ≤ V+ ≤ 5.5V
CMVR
AVOL
(4)
Common Mode Voltage Range
Open Loop Voltage Gain
(2)
VCM = 4.5V
Input Offset Current
TCIOS
Max
±500
±600
Input Bias Current
IOS
(2)
(3)
(3)
(4)
TCVOS
(1)
Typ
Large Signal CMRR ≥ 80 dB
Units
μV
μV/°C
nA
nA
nA/°C
dB
dB
117
0
5
RL = 10 kΩ to V+/2
VOUT = 0.5V to 4.5V
112
104
130
RL = 2 kΩ to V+/2
VOUT = 0.5V to 4.5V
110
94
119
V
dB
Electrical Table values apply only for factory testing conditions at the temperature indicated. Factory testing conditions result in very
limited self-heating of the device such that TJ = TA. No specification of parametric performance is indicated in the electrical tables under
conditions of internal self-heating where TJ > TA. Absolute maximum Ratings indicate junction temperature limits beyond which the
device maybe permanently degraded, either mechanically or electrically.
All limits are specified by testing, statistical analysis or design.
Typical values represent the most likely parametric norm as determined at the time of characterization. Actual typical values may vary
over time and will also depend on the application and configuration. The typical values are not tested and are not ensured on shipped
production material.
Ambient production test is performed at 25°C with a variance of ±3°C.
Submit Documentation Feedback
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5V Electrical Characteristics (1) (continued)
Unless otherwise specified, all limits are ensured for TA = 25°C, V+ = 5V, V− = 0V, VCM = V+/2, RL > 10 kΩ to V+/2. Boldface
limits apply at the temperature extremes.
Parameter
Test Conditions
(2)
Min
Typ
(3)
Max
RL = 10 kΩ to V+/2
8
50
75
RL = 2 kΩ to V+/2
24
50
75
RL = 10 kΩ to V+/2
9
50
75
RL = 2 kΩ to V+/2
23
50
75
Output Voltage Swing High
VOUT
Output Voltage Swing Low
IOUT
IS
Output Current
Supply Current
(Per Channel)
Sourcing, VOUT = V+/2
VIN (diff) = 100 mV
33
27
47
Sinking, VOUT = V+/2
VIN (diff) = -100 mV
30
25
49
(2)
Units
mV from
either rail
mA
VCM = 4.5V
2.2
3.0
3.7
VCM = 0.5V
2.5
3.4
4.2
mA
SR
Slew Rate
AV = +1, CL = 10 pF, RL = 10 kΩ to
V+/2,
VOUT = 2 VPP
2.4
V/μs
GBW
Gain Bandwidth
CL = 20 pF, RL = 10 kΩ to V+/2
22
MHz
+
GM
Gain Margin
CL = 20 pF, RL = 10 kΩ to V /2
12
dB
ΦM
Phase Margin
CL = 20 pF, RL = 10 kΩ to V+/2
65
deg
RIN
Input Resistance
Differential Mode
38
kΩ
151
MΩ
THD+N
Total Harmonic Distortion + Noise
AV = 1, f = 1 kHz, Amplitude = 1V
0.001
%
Input Referred Voltage Noise
Density
f = 1 kHz, VCM = 4.5V
2.9
f = 1 kHz, VCM = 0.5V
2.9
Input Voltage Noise
0.1 Hz to 10 Hz
78
Input Referred Current Noise
Density
f = 1 kHz, VCM = 4.5V
1.1
f = 1 kHz, VCM = 0.5V
2.2
en
in
Common Mode
nV/√Hz
nVPP
pA/√Hz
Connection Diagrams
OUT
-
V
5
1
N/C
-IN
2
+
+IN
+
V
-
3
4
+IN
2
3
8
+
7
6
N/C
+
V
OUT
-IN
V
-
Figure 3. 5-Pin SOT-23
Top View
6
1
4
5
N/C
Figure 4. 8-Pin SOIC
Top View
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Typical Performance Characteristics
Unless otherwise noted: TA = 25°C, RL > 10 kΩ, VCM = VS/2.
Offset Voltage Distribution
TCVOS Distribution
10
16
VS = 2.5V
VS = 2.5V
VCM = 2V
14
VCM = 2V
12
-40°C d TA d 25°C
PERCENTAGE (%)
PERCENTAGE (%)
8
6
4
10
8
6
4
2
2
0
-50 -40 -30 -20 -10 0
0
-0.5
10 20 30 40 50
0
VOS (PV)
0.5
Figure 5.
1.5
Figure 6.
Offset Voltage Distribution
TCVOS Distribution
10
16
VS = 3.3V, 5V
VS = 3.3V, 5V
VCM = VS -0.5V
14
VCM = VS -0.5V
12
-40°C d TA d 25°C
PERCENTAGE (%)
8
PERCENTAGE (%)
1
TCVOS (PV/°C)
6
4
10
8
6
4
2
2
0
-50 -40 -30 -20 -10 0
0
-0.5
10 20 30 40 50
0
VOS (PV)
Figure 7.
1
1.5
Figure 8.
Offset Voltage Distribution
TCVOS Distribution
10
25
VS = 2.5V, 3.3V
VS = 2.5V
VCM = 0.5V
VCM = 0.5V
8
20
PERCENTAGE (%)
PERCENTAGE (%)
0.5
TCVOS (PV/°C)
6
4
2
-40°C d TA d 25°C
15
10
5
0
-50 -40 -30 -20 -10 0
10 20 30 40 50
VOS (PV)
0
-1.5
-1
-0.5
0
0.5
TCVOS (PV/°C)
Figure 9.
Figure 10.
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Typical Performance Characteristics (continued)
Unless otherwise noted: TA = 25°C, RL > 10 kΩ, VCM = VS/2.
Offset Voltage Distribution
TCVOS Distribution
14
25
VS = 5V
VS = 3.3V, 5V
12 VCM = 0.5V
20
PERCENTAGE (%)
PERCENTAGE (%)
10
8
6
4
VCM = 0.5V
-40°C d TA d 125°C
15
10
5
2
0
-40 -30 -20 -10
0
10
20
30
0
-1.5
40
-1
-0.5
TCVOS (PV/°C)
Figure 11.
Figure 12.
Offset Voltage
vs.
Temperature
0.5
Offset Voltage vs. Temperature
60
20
VS = 2.5V, 3.3V, 5V
VS = 2.5V, 3.3V, 5V
VCM = 0.5V
VCM = VS - 0.5V
40 5 TYPICAL PARTS
15
20
10
VOS (PV)
VOS (PV)
0
VOS (PV)
0
-20
5 TYPICAL PARTS
5
0
-40
-40 -20
0
20
40
60
-5
-40 -20
80 100 120
0
20
40
60
80 100 120
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 13.
Figure 14.
PSRR vs. Frequency
CMRR
vs.
Frequency
160
0
VS = 2.5V, 3.3V, 5V
140
-20
-PSRR
120
-60
CMRR (dB)
PSRR (dB)
-40
VS = 5V
-80 V = 2.5V
S
+PSRR
-100
60
20
VS = 5V
100
1k
10k
100k
1M
10M
0
100
1k
10k
100k
1M
10M
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 15.
8
80
40
VS = 3.3V
-120
-140
10
100
Figure 16.
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Typical Performance Characteristics (continued)
Unless otherwise noted: TA = 25°C, RL > 10 kΩ, VCM = VS/2.
Offset Voltage
vs.
Supply Voltage
Offset Voltage
vs.
VCM
5
100
VS = 2.5V
50
-5
VOS (PV)
OFFSET VOLTAGE (PV)
75
25°C
0
-40°C
-10
125°C
25
85°C
25°C
0
-15
-40°C
-25
85°C
-20
-50
-25
1.5
125°C
2
2.5
3
3.5
4
4.5
5
-75
5.5
0
0.5
1
SUPPLY VOLTAGE (V)
Figure 18.
Offset Voltage
vs.
VCM
Offset Voltage
vs.
VCM
2.5
100
VS = 5V
VS = 3.3V
75
75
50
50
VOS (PV)
125°C
VOS (PV)
2
Figure 17.
100
85°C
25
25°C
0
-40°C
-25
125°C
25
85°C
25°C
0
-40°C
-25
-50
-50
-75
-75
0
0.5
1
1.5
2
2.5
3 3.3
0
1
2
3
4
5
VCM (V)
VCM (V)
Figure 19.
Figure 20.
Input Offset Voltage Time Drift
Slew Rate
vs.
Supply Voltage
1
3.4
RISING EDGE
3.2
VS = 5V
0.8
RL = 2 k:
SLEW RATE (V/Ps)
OFFSET VOLTAGE DRIFT (PV)
1.5
VCM (V)
0.6
0.4
3
2.8
FALLING EDGE
2.6
AV = +1
2.4
VIN = 1 VPP
0.2
2.2
0
0
50
100
150
200
250
300
2
1.5
RL = 10 k:
CL = 10 pF
2
2.5
3
3.5
4
4.5
5
5.5
SUPPLY VOLTAGE (V)
TIME (s)
Figure 21.
Figure 22.
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Typical Performance Characteristics (continued)
Unless otherwise noted: TA = 25°C, RL > 10 kΩ, VCM = VS/2.
Time Domain Voltage Noise
Time Domain Voltage Noise
Figure 23.
Figure 24.
Time Domain Voltage Noise
Output Voltage
vs.
Output Current
1000
VS = 2.5V, 3.3V, 5V
VOUT FROM RAIL (mV)
800
VS = 2.5V
600
400
SINK
200
0
-200
-400
SOURCE
-600
-800
0
5
10
15
20
25
30
OUTPUT CURRENT (mA)
Figure 25.
Figure 26.
Input Bias Current
vs.
VCM
Input Bias Current
vs.
VCM
100
100
VS = 2.5V
125°C
60
85°C
40
25°C
20
0
-20
-40
-40°C
-60
0
-20
1.5
2
2.5
-40°C
-40
-60
-80
1
25°C
20
-100
0.5
85°C
40
-80
0
0.5
1
1.5
2
2.5
3
3.5
VCM (V)
VCM (V)
Figure 27.
10
60
-100
0
VS = 3.3V
125°C
80
INPUT BIAS CURRENT (nA)
INPUT BIAS CURRENT (nA)
80
Figure 28.
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Typical Performance Characteristics (continued)
Unless otherwise noted: TA = 25°C, RL > 10 kΩ, VCM = VS/2.
Input Bias Current
vs.
VCM
Open Loop Frequency Response Over Temperature
100
100
INPUT BIAS CURRENT (nA)
225
VS = 5V
125°C
80
GAIN
80
180
60
40
60
20
GAIN (dB)
25°C
0
-20
-40
PHASE
20
45
VS = 2.5V, TA = 25°C
-40°C
0
0
VS = 2.5V, 3.3V, 5V
-20 RL = 10 k:
TA = -40°C, 25°C, 85°C, 125°C
-40
1M
10M
100k
1k
10k
-80
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
VCM (V)
Open Loop Frequency Response
Open Loop Frequency Response
100
225
VS = 5V
GAIN
GAIN
180
80
135
60
RL = 10 k: 180
CL = 20 pF
135
-40°C
90
25°C
90
40
PHASE
20 V = 2.5V, C = 100 pF,
S
L
45
RL = 10 k:
GAIN (dB)
GAIN (dB)
RL = 2 k:
PHASE (°)
VS = 5V, CL = 20 pF,
40
PHASE
20
45
85°C
0
0
VS = 2.5V, 3.3V, 5V
-20
-40
RL = 2 k:, 10 k:
1k
10k
100k
1M
10M
-90
100M
-40
1k
10k
10M
Figure 32.
THD+N
vs.
Frequency
THD+N
vs.
Output Voltage
-90
100M
1
RL = 100 k:
RL = 100 k:
CL = 10 pF
CL = 10 pF
f = 1 kHz
VO = VS -1V
0.1
VS = 2.5V
THD+N (%)
THD+N (%)
1M
Figure 31.
1
0.01
100k
-45
FREQUENCY (Hz)
FREQUENCY (Hz)
0.1
0
125°C
-20
-45
CL = 20 pF, 50 pF, 100 pF
PHASE (°)
225
60
-90
100M
Figure 30.
100
80
-45
FREQUENCY (Hz)
Figure 29.
0
135
90
40
-60
-100
VS = 5V, TA = -40°C
PHASE (°)
85°C
VS = 3.3V
0.01
0.001
VS = 2.5V
0.001
VS = 3.3V
VS = 5V
VS = 5V
0.0001
10
100
1k
10k
100k
0.0001
FREQUENCY (Hz)
0.1
1
10
VOUT (VPP)
Figure 33.
Figure 34.
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Typical Performance Characteristics (continued)
Unless otherwise noted: TA = 25°C, RL > 10 kΩ, VCM = VS/2.
Small Signal Step Response
20 mV/DIV
500 mV/DIV
Large Signal Step Response
VS = 5V
VIN = 2 VPP
f = 10 kHz
VS = 5V
VIN = 100 mVPP
f = 10 kHz
AV = +1
AV = +1
RL = 10 k:
RL = 10 k:
CL = 10 pF
CL = 10 pF
Figure 35.
Figure 36.
Large Signal Step Response
Small Signal Step Response
200 mV/DIV
10 Ps/DIV
1 V/DIV
10 Ps/DIV
VS = 5V
VIN = 400 mVPP
f = 10 kHz
VS = 5V
VIN = 100 mVPP
f = 10 kHz
AV = +10
AV = +10
RL = 10 k:
RL = 10 k:
CL = 10 pF
CL = 10 pF
10 Ps/DIV
10 Ps/DIV
Figure 37.
Figure 38.
Supply Current
vs.
Supply Voltage
Output Swing High
vs.
Supply Voltage
3.5
40
RL = 2 k:
3
125°C
VOUT FROM RAIL (mV)
SUPPLY CURRENT (mA)
35
85°C
2.5
25°C
-40°C
2
30
125°C
25
85°C
20
-40°C
15
25°C
10
5
1.5
1.5
12
2
2.5
3
3.5
4
4.5
5
5.5
0
1.5
2
2.5
3
3.5
4
4.5
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
Figure 39.
Figure 40.
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5.5
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Typical Performance Characteristics (continued)
Unless otherwise noted: TA = 25°C, RL > 10 kΩ, VCM = VS/2.
Output Swing Low
vs.
Supply Voltage
Sinking Current vs, Supply Voltage
60
40
-40°C
RL = 2 k:
25°C
50
125°C
30
25
ISINK (mA)
VOUT FROM RAIL (mV)
35
85°C
20
15
85°C
40
125°C
30
-40°C
25°C
10
20
5
0
1.5
2
2.5
3
3.5
4
4.5
5
10
1.5
5.5
2
2.5
3
3.5
4
4.5
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
Figure 41.
Figure 42.
5
5.5
Sourcing Current
vs.
Supply Voltage
60
-40°C
ISOURCE (mA)
50
25°C
40
125°C
30
85°C
20
10
1.5
2
2.5
3
3.5
4
4.5
5
5.5
SUPPLY VOLTAGE (V)
Figure 43.
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APPLICATION INFORMATION
LMP7731
The LMP7731 is a single, low noise, rail-to-rail input and output, and low voltage amplifier.
The low input voltage noise of only 2.9 nV/√Hz with a 1/f corner at 3 Hz makes the LMP7731 ideal for sensor
applications where DC accuracy is of importance.
The LMP7731 has a high gain bandwidth of 22 MHz. This wide bandwidth enables use of the amplifier at higher
gain settings while retaining usable bandwidth for the application. This is particularly beneficial when system
designers need to use sensors with very limited output voltage range as it allows larger gains in one stage which
in turn increases the signal to noise ratio.
The LMP7731 has proprietary input bias cancellation circuitry on the input stages. This allows the LMP7731 to
have only about 1.5 nA bias current with a bipolar input stage. This low input bias current, paired with the
inherent lower input voltage noise of bipolar input stages makes the LMP7731 an excellent choice for precision
applications. The combination of low input bias current, and low input voltage noise enables the user to achieve
unprecedented accuracy and higher signal integrity.
Texas Instruments is heavily committed to precision amplifiers and the market segment they serve. Technical
support and extensive characterization data are available for sensitive applications or applications with a
constrained error budget.
The LMP7731 is offered in the space saving 5-Pin SOT-23 and 8-Pin SOIC packages. These small packages are
ideal solutions for area constrained PC boards and portable electronics.
INPUT BIAS CURRENT CANCELLATION
The LMP7731 has proprietary input bias current cancellation circuitry on their input stages.
The LMP7731 has rail-to-rail input. This is achieved by having two input stages in parallel. Figure 44 shows only
one of the input stages as the circuitry is symmetrical for both stages.
Figure 44 shows that as the common mode voltage gets closer to one of the extreme ends, current I1
significantly increases. This increased current shows as an increase in voltage drop across resistor R1 equal to
I1*R1 on IN+ of the amplifier. This voltage contributes to the offset voltage of the amplifier. When common mode
voltage is in the mid-range, the transistors are operating in the linear region and I1 is significantly small. The
voltage drop due to I1 across R1 can be ignored as it is orders of magnitude smaller than the amplifier's input
offset voltage.
As the common mode voltage gets closer to one of the rails, the offset voltage generated due to I1 increases and
becomes comparable to the amplifiers offset voltage.
IBIAS CANCELLATION CIRCUIT
V
+
INPUT STAGE
+
V
R
R
C1 C2
R1
IN
+
I1
Q1
Q2
R2
IN
-
Figure 44. Input Bias Current Cancellation
14
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INPUT VOLTAGE NOISE MEASUREMENT
The LMP7731 has very low input voltage noise. The peak-to-peak input voltage noise of the LMP7731 can be
measured using the test circuit shown in Figure 45
0.1 PF
100 k:
10:
2 k:
LMP7731
+
+
LMP7731
VOLTAGE GAIN = 50,000
4.7 PF
-
4.3 k:
22 PF
2.2 PF
110 k:
100 k:
SCOPE
x1
RIN = 1M
24.3 k:
0.1 PF
Figure 45. 0.1 Hz to 10 Hz Noise Test Circuit
The frequency response of this noise test circuit at the 0.1 Hz corner is defined by only one zero. The test time
for the 0.1 Hz to 10 Hz noise measurement using this configuration should not exceed 10 seconds, as this time
limit acts as an additional zero to reduce or eliminate the noise contributions of noise from frequencies below 0.1
Hz.
Figure 46 shows typical peak-to-peak noise for the LMP7731 measured with the circuit in Figure 45 for the
LMP7731.
Figure 46. 0.1 Hz to 10 Hz Input Voltage Noise
Measuring the very low peak-to-peak noise performance of the LMP7731, requires special testing attention. In
order to achieve accurate results, the device should be warmed up for at least five minutes. This is so that the
input offset voltage of the op amp settles to a value. During this warm up period, the offset can typically change
by a few µV because the chip temperature increases by about 30°C. If the 10 seconds of the measurement is
selected to include this warm up time, some of this temperature change might show up as the measured noise.
Figure 47 shows the start-up drift of five typical LMP7731 units.
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OFFSET VOLTAGE DRIFT (PV)
1
VS = 5V
0.8
RL = 2 k:
0.6
0.4
0.2
0
50
0
100
150
200
250
300
TIME (s)
Figure 47. Start-Up Input Offset Voltage Drift
During the peak-to-peak noise measurement, the LMP7731 must be shielded. This prevents offset variations due
to airflow. Offset can vary by a few nV due to this airflow and that can invalidate measurements of input voltage
noise with a magnitude which is in the same range. For similar reasons, sudden motions must also be restricted
in the vicinity of the test area. The feed-through which results from this motion could increase the observed noise
value which in turn would invalidate the measurement.
DIODES BETWEEN THE INPUTS
The LMP7731 has a set of anti-parallel diodes between the input pins as shown in Figure 48. These diodes are
present to protect the input stage of the amplifier. At the same time, they limit the amount of differential input
voltage that is allowed on the input pins. A differential signal larger than the voltage needed to turn on the diodes
might cause damage to the diodes. The differential voltage between the input pins should be limited to ±3 diode
drops or the input current needs to be limited to ±20 mA.
V
ESD
IN
+
+
V
R1
ESD
R2
+
IN
-
ESD
ESD
-
-
V
V
Figure 48. Anti-Parallel Diodes between Inputs
DRIVING AN ADC
Analog to Digital Converters, ADCs, usually have a sampling capacitor on their input. When the ADC's input is
directly connected to the output of the amplifier a charging current flows from the amplifier to the ADC. This
charging current causes a momentary glitch that can take some time to settle. There are different ways to
minimize this effect. One way is to slow down the sampling rate. This method gives the amplifier sufficient time to
stabilize its output. Another way to minimize the glitch caused by the switch capacitor is to have an external
capacitor connected to the input of the ADC. This capacitor is chosen so that its value is much larger than the
internal switching capacitor and it will hence provide the voltage needed to quickly and smoothly charge the
16
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ADC's sampling capacitor. Since this large capacitor will be loading the output of the amplifier as well, an
isolation resistor is needed between the output of the amplifier and this capacitor. The isolation resistor, RISO,
separates the additional load capacitance from the output of the amplifier and will also form a low-pass filter and
can be designed to provide noise reduction as well as anti-aliasing. The drawback to having RISO is that it
reduces signal swing since there is some voltage drop across it.
Figure 49 (a) shows the ADC directly connected to the amplifier. To minimize the glitch in this setting, a slower
sample rate needs to be used. Figure 49 (b) shows RISO and an external capacitor used to minimize the glitch.
FEEDBACK
NETWORK
(a)
ADC
V+
SENSOR
INPUT
NETWORK
V-
(b)
FEEDBACK
NETWORK
V+
ADC
RISO
SENSOR
INPUT
NETWORK
V-
C
Figure 49. Driving an ADC
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REVISION HISTORY
Changes from Revision D (March 2013) to Revision E
•
18
Page
Changed layout of National Data Sheet to TI format .......................................................................................................... 17
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PACKAGE OPTION ADDENDUM
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10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
LMP7731MA/NOPB
ACTIVE
SOIC
D
8
95
RoHS & Green
SN
Level-1-260C-UNLIM
LMP77
31MA
LMP7731MAX/NOPB
ACTIVE
SOIC
D
8
2500
RoHS & Green
SN
Level-1-260C-UNLIM
LMP77
31MA
LMP7731MF/NOPB
ACTIVE
SOT-23
DBV
5
1000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
AY3A
LMP7731MFE/NOPB
ACTIVE
SOT-23
DBV
5
250
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
AY3A
LMP7731MFX/NOPB
ACTIVE
SOT-23
DBV
5
3000
RoHS & Green
SN
Level-1-260C-UNLIM
-40 to 125
AY3A
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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