LMP2231
LMP2231 Single Micropower, 1.6V, Precision Operational Amplifier with CMOS
Inputs
Literature Number: SNOSB01D
LMP2231 Single
June 25, 2010
Micropower, 1.6V, Precision Operational Amplifier with
CMOS Inputs
General Description
The LMP2231 is a single micropower precision amplifier de-
signed for battery powered applications. The 1.6V to 5.5V
operating supply voltage range and quiescent power con-
sumption of only 16 μW extend the battery life in portable
battery operated systems. The LMP2231 is part of the
LMP® precision amplifier family. The high impedance CMOS
input makes it ideal for instrumentation and other sensor in-
terface applications.
The LMP2231 has a maximum offset of 150 µV and maximum
offset voltage drift of only 0.4 µV/°C along with low bias cur-
rent of only ±20 fA. These precise specifications make the
LMP2231 a great choice for maintaining system accuracy and
long term stability.
The LMP2231 has a rail-to-rail output that swings 15 mV from
the supply voltage, which increases system dynamic range.
The common mode input voltage range extends 200 mV be-
low the negative supply, thus the LMP2231 is ideal for use in
single supply applications with ground sensing.
The LMP2231 is offered in 5-Pin SOT23 and 8-pin SOIC
packages.
The dual and quad versions of this product are also available.
The dual, LMP2232 is offered in 8-pin SOIC and MSOP. The
quad, LMP2234 is offered in 14-pin SOIC and TSSOP.
Features
(For VS = 5V, TA = 25°C, Typical unless otherwise noted)
Supply current 10 µA
Operating voltage range 1.6V to 5.5V
TCVOS (LMP2231A) ±0.4 µV/°C (max)
TCVOS (LMP2231B) ±2.5µV/°C (max)
VOS ±150 µV (max)
Input bias current 20 fA
PSRR 120 dB
CMRR 97 dB
Open loop gain 120 dB
Gain bandwidth product 130 kHz
Slew rate 58 V/ms
Input voltage noise, f = 1 kHz 60 nV/Hz
Temperature range –40°C to 125°C
Applications
Precision instrumentation amplifiers
Battery powered medical instrumentation
High Impedance Sensors
Strain gauge bridge amplifier
Thermocouple amplifiers
Typical Application
30033874
Strain Gauge Bridge Amplifier
LMP® is a registered trademark of National Semiconductor Corporation.
© 2010 National Semiconductor Corporation 300338 www.national.com
LMP2231 Single Micropower, 1.6V, Precision, Operational Amplifier with CMOS Inputs
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
ESD Tolerance (Note 2)
Human Body Model 2000V
Machine Model 100V
Differential Input Voltage ±300 mV
Supply Voltage (VS = V+ - V)6V
Voltage on Input/Output Pins V+ + 0.3V, V – 0.3V
Storage Temperature Range −65°C to 150°C
Junction Temperature (Note 3) 150°C
For soldering specifications:
see product folder at www.national.com and
www.national.com/ms/MS/MS-SOLDERING.pdf
Operating Ratings (Note 1)
Operating Temperature Range (Note 3) −40°C to 125°C
Supply Voltage (VS = V+ - V)1.6V to 5.5V
Package Thermal Resistance (θJA) (Note 3)
5-Pin SOT23 160.6 °C/W
8-Pin SOIC 116.2 °C/W
5V DC Electrical Characteristics (Note 4) Unless otherwise specified, all limits guaranteed for TA = 25°C,
V+ = 5V, V = 0V, VCM = VO = V+/2, and RL > 1 MΩ. Boldface limits apply at the temperature extremes.
Symbol Parameter Conditions Min
(Note 6)
Typ
(Note 5)
Max
(Note 6)
Units
VOS Input Offset Voltage ±10 ±150
±230 μV
TCVOS Input Offset Voltage Drift LMP2231A ±0.3 ±0.4 μV/°C
LMP2231B ±0.3 ±2.5
IBIAS Input Bias Current 0.02 ±1
±50 pA
IOS Input Offset Current 5 fA
CMRR Common Mode Rejection Ratio 0V VCM 4V 81
80
97 dB
PSRR Power Supply Rejection Ratio 1.6V V+ 5.5V
V = 0V, VCM = 0V
83
83
120 dB
CMVR Common Mode Voltage Range CMRR 80 dB
CMRR 79 dB
−0.2
−0.2
4.2
4.2 V
AVOL Large Signal Voltage Gain VO = 0.3V to 4.7V
RL = 10 k to V+/2
110
108
120 dB
VOOutput Swing High RL = 10 k to V+/2
VIN(diff) = 100 mV
17 50
50 mV
from either
rail
Output Swing Low RL = 10 k to V+/2
VIN(diff) = −100 mV
17 50
50
IOOutput Current (Note 7) Sourcing, VO to V
VIN(diff) = 100 mV
27
19
30
mA
Sinking, VO to V+
VIN(diff) = −100 mV
17
12
22
ISSupply Current 10 16
18 µA
5V AC Electrical Characteristics (Note 4) Unless otherwise specified, all limits guaranteed for TA = 25°C,
V+ = 5V, V = 0V, VCM = VO = V+/2, and RL > 1 MΩ. Boldface limits apply at the temperature extremes.
Symbol Parameter Conditions Min
(Note 6)
Typ
(Note 5)
Max
(Note 6)
Units
GBW Gain-Bandwidth Product CL = 20 pF, RL = 10 k 130 kHz
SR Slew Rate AV = +1 Falling Edge 33
32
58
V/ms
Rising Edge 33
32
48
θ m Phase Margin CL = 20 pF, RL = 10 k 78 deg
GmGain Margin CL = 20 pF, RL = 10 k 27 dB
www.national.com 2
LMP2231 Single
Symbol Parameter Conditions Min
(Note 6)
Typ
(Note 5)
Max
(Note 6)
Units
enInput-Referred Voltage Noise Density f = 1 kHz 60 nV/
Input-Referred Voltage Noise 0.1 Hz to 10 Hz 2.3 μVPP
inInput-Referred Current Noise f = 1 kHz 10 fA/
THD+N Total Harmonic Distortion + Noise f = 100 Hz, RL = 10 k 0.002 %
3.3V DC Electrical Characteristics (Note 4) Unless otherwise specified, all limits guaranteed for
TA = 25°C, V+ = 3.3V, V = 0V, VCM = VO = V+/2, and RL > 1 MΩ. Boldface limits apply at the temperature extremes.
Symbol Parameter Conditions Min
(Note 6)
Typ
(Note 5)
Max
(Note 6)
Units
VOS Input Offset Voltage ±10 ±160
±250 μV
TCVOS Input Offset Voltage Drift LMP2231A ±0.3 ±0.4 μV/°C
LMP2231B ±0.3 ±2.5
IBIAS Input Bias Current 0.02 ±1
±50 pA
IOS Input Offset Current 5 fA
CMRR Common Mode Rejection Ratio 0V VCM 2.3V 79
77
92 dB
PSRR Power Supply Rejection Ratio 1.6V V+ 5.5V
V = 0V, VCM = 0V
83
83
120 dB
CMVR Common Mode Voltage Range CMRR 78 dB
CMRR 77 dB
−0.2
−0.2
2.5
2.5 V
AVOL Large Signal Voltage Gain VO = 0.3V to 3V
RL = 10 k to V+/2
108
107
120 dB
VOOutput Swing High RL = 10 k to V+/2
VIN(diff) = 100 mV
14 50
50 mV
from either
rail
Output Swing Low RL = 10 k to V+/2
VIN(diff) = −100 mV
14 50
50
IOOutput Current (Note 7) Sourcing, VO to V
VIN(diff) = 100 mV
11
8
14
mA
Sinking, VO to V+
VIN(diff) = −100 mV
8
5
11
ISSupply Current 10 15
16 µA
3.3V AC Electrical Characteristics (Note 4) Unless otherwise is specified, all limits guaranteed for
TA = 25°C, V+ = 3.3V, V = 0V, VCM = VO = V+/2, and RL > 1 MΩ. Boldface limits apply at the temperature extremes.
Symbol Parameter Conditions Min
(Note 6)
Typ
(Note 5)
Max
(Note 6)
Units
GBW Gain-Bandwidth Product CL = 20 pF, RL = 10 k 128 kHz
SR Slew Rate AV = +1, CL = 20 pF
RL = 10 k
Falling Edge 58 V/ms
Rising Edge 48
θ m Phase Margin CL = 20 pF, RL = 10 k 76 deg
GmGain Margin CL = 20 pF, RL = 10 k 26 dB
enInput-Referred Voltage Noise Density f = 1 kHz 60 nV/
Input-Referred Voltage Noise 0.1 Hz to 10 Hz 2.4 μVPP
inInput-Referred Current Noise f = 1 kHz 10 fA/
THD+N Total Harmonic Distortion + Noise f = 100 Hz, RL = 10 k 0.003 %
3 www.national.com
LMP2231 Single
2.5V DC Electrical Characteristics (Note 4) Unless otherwise specified, all limits guaranteed for
TA = 25°C, V+ = 2.5V, V = 0V, VCM = VO = V+/2, and RL > 1MΩ. Boldface limits apply at the temperature extremes.
Symbol Parameter Conditions Min
(Note 6)
Typ
(Note 5)
Max
(Note 6)
Units
VOS Input Offset Voltage ±10 ±190
±275 μV
TCVOS Input Offset Voltage Drift LMP2231A ±0.3 ±0.4 μV/°C
LMP2231B ±0.3 ±2.5
IBIAS Input Bias Current 0.02 ±1.0
±50 pA
IOS Input Offset Current 5 fA
CMRR Common Mode Rejection Ratio 0V VCM 1.5V 77
76
91 dB
PSRR Power Supply Rejection Ratio 1.6V V+ 5.5V
V = 0V, VCM = 0V
83
83
120 dB
CMVR Common Mode Voltage Range CMRR 77 dB
CMRR 76 dB
−0.2
−0.2
1.7
1.7 V
AVOL Large Signal Voltage Gain VO = 0.3V to 2.2V
RL = 10 k to V+/2
104
104
120 dB
VOOutput Swing High RL = 10 k to V+/2
VIN(diff) = 100 mV
12 50
50 mV
from either
rail
Output Swing Low RL = 10 k to V+/2
VIN (diff) = −100 mV
13 50
50
IOOutput Current (Note 7) Sourcing, VO to V
VIN(diff) = 100 mV
5
4
8
mA
Sinking, VO to V+
VIN(diff) = −100 mV
3.5
2.5
7
ISSupply Current 10 14
15 µA
2.5V AC Electrical Characteristics (Note 4) Unless otherwise specified, all limits guaranteed for
TA = 25°C, V+ = 2.5V, V = 0V, VCM = VO = V+/2, and RL > 1MΩ. Boldface limits apply at the temperature extremes.
Symbol Parameter Conditions Min
(Note 6)
Typ
(Note 5)
Max
(Note 6)
Units
GBW Gain-Bandwidth Product CL = 20 pF, RL = 10 k 128 kHz
SR Slew Rate AV = +1, CL = 20 pF
RL = 10 k
Falling Edge 58 V/ms
Rising Edge 48
θ m Phase Margin CL = 20 pF, RL = 10 k 74 deg
GmGain Margin CL = 20 pF, RL = 10 k 26 dB
enInput-Referred Voltage Noise Density f = 1 kHz 60 nV/
Input-Referred Voltage Noise 0.1 Hz to 10 Hz 2.5 μVPP
inInput-Referred Current Noise f = 1 kHz 10 fA/
THD+N Total Harmonic Distortion + Noise f = 100 Hz, RL = 10 k 0.005 %
www.national.com 4
LMP2231 Single
1.8V DC Electrical Characteristics (Note 4) Unless otherwise specified, all limits guaranteed for
TA = 25°C, V+ = 1.8V, V = 0V, VCM = VO = V+/2, and RL > 1 MΩ. Boldface limits apply at the temperature extremes.
Symbol Parameter Conditions Min
(Note 6)
Typ
(Note 5)
Max
(Note 6)
Units
VOS Input Offset Voltage ±10 ±230
±325 μV
TCVOS Input Offset Voltage Drift LMP2231A ±0.3 ±0.4 μV/°C
LMP2231B ±0.3 ±2.5
IBIAS Input Bias Current 0.02 ±1.0
±50 pA
IOS Input Offset Current 5 fA
CMRR Common Mode Rejection Ratio 0V VCM 0.8V 76
75
92 dB
PSRR Power Supply Rejection Ratio 1.6V V+ 5.5V
V = 0V, VCM = 0V
83
83
120 dB
CMVR Common Mode Voltage Rang CMRR 76 dB
CMRR 75 dB
−0.2
0
1.0
1.0 V
AVOL Large Signal Voltage Gain VO = 0.3V to 1.5V
RL = 10 k to V+/2
103
103
120 dB
VOOutput Swing High RL = 10 k to V+/2
VIN(diff) = 100 mV
12 50
50 mV
from either
rail
Output Swing Low RL = 10 k to V+/2
VIN(diff) = −100 mV
13 50
50
IOOutput Current (Note 7) Sourcing, VO to V
VIN(diff) = 100 mV
2.5
2
5
mA
Sinking, VO to V+
VIN(diff) = −100 mV
2
1.5
5
ISSupply Current 10 14
15 µA
1.8V AC Electrical Characteristics (Note 4) Unless otherwise is specified, all limits guaranteed for
TA = 25°C, V+ = 1.8V, V = 0V, VCM = VO = V+/2, and RL > 1 MΩ. Boldface limits apply at the temperature extremes.
Symbol Parameter Conditions Min
(Note 6)
Typ
(Note 5)
Max
(Note 6)
Units
GBW Gain-Bandwidth Product CL = 20 pF, RL = 10 k 127 kHz
SR Slew Rate AV = +1, CL = 20 pF
RL = 10 k
Falling Edge 58 V/ms
Rising Edge 48
θ m Phase Margin CL = 20 pF, RL = 10 k 70 deg
GmGain Margin CL = 20 pF, RL = 10 k 25 dB
enInput-Referred Voltage Noise Density f = 1 kHz 60 nV/
Input-Referred Voltage Noise 0.1 Hz to 10 Hz 2.4 μVPP
inInput-Referred Current Noise f = 1 kHz 10 fA/
THD+N Total Harmonic Distortion + Noise f = 100 Hz, RL = 10 k 0.005 %
5 www.national.com
LMP2231 Single
Note 1: Absolute Maximum Ratings indicate limits beyond which damage may occur. Operating Ratings indicate conditions for which the device is intended to
be functional, but specific performance is not guaranteed. For guaranteed specifications and test conditions, see the Electrical Characteristics.
Note 2: 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).
Note 3: 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.
Note 4: 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 guarantee 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 may be permanently degraded, either mechanically or electrically.
Note 5: Typical values represent the most likely parametric norm 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 guaranteed on shipped production material.
Note 6: All limits are guaranteed by testing, statistical analysis or design.
Note 7: The short circuit test is a momentary open loop test.
Connection Diagrams
5-Pin SOT23
30033802
Top View
8-Pin SOIC
30033842
Top View
Ordering Information
Package Part Number Temperature
Range
Package Marking Transport Media NSC Drawing
5-Pin SOT23
LMP2231AMF
−40°C to 125°C
AL5A
1k Units Tape and Reel
MF05A
LMP2231AMFE 250 Units Tape and Reel
LMP2231AMFX 3k Units Tape and Reel
LMP2231BMF
AL5B
1k Units Tape and Reel
LMP2231BMFE 250 Units Tape and Reel
LMP2231BMFX 3k Units Tape and Reel
8-Pin SOIC
LMP2231AMA
LMP2231AMA
95 Units/Rail
M08A
LMP2231AMAE 250 Units Tape and Reel
LMP2231AMAX 2.5k Units Tape and Reel
LMP2231BMA
LMP2231BMA
95 Units/Rail
LMP2231BMAE 250 Units Tape and Reel
LMP2231BMAX 2.5k Units Tape and Reel
www.national.com 6
LMP2231 Single
Typical Performance Characteristics Unless otherwise Specified: TA = 25°C, VS = 5V, VCM = VS/2, where
VS = V+ - V
Offset Voltage Distribution
30033807
TCVOS Distribution
30033811
Offset Voltage Distribution
30033806
TCVOS Distribution
30033810
Offset Voltage Distribution
30033805
TCVOS Distribution
30033809
7 www.national.com
LMP2231 Single
Offset Voltage Distribution
30033873
TCVOS Distribution
30033869
Offset Voltage vs. VCM
30033818
Offset Voltage vs. VCM
30033865
Offset Voltage vs. VCM
30033864
Offset Voltage vs. VCM
30033872
www.national.com 8
LMP2231 Single
Offset Voltage vs. Temperature
30033871
Offset Voltage vs. Supply Voltage
30033870
Time Domain Voltage Noise
30033833
Time Domain Voltage Noise
30033834
Time Domain Voltage Noise
30033832
Time Domain Voltage Noise
30033831
9 www.national.com
LMP2231 Single
Input Bias Current vs. VCM
30033855
Input Bias Current vs. VCM
30033856
Input Bias Current vs. VCM
30033857
Input Bias Current vs. VCM
30033858
Input Bias Current vs. VCM
30033859
Input Bias Current vs. VCM
30033860
www.national.com 10
LMP2231 Single
Input Bias Current vs. VCM
30033861
Input Bias Current vs. VCM
30033862
PSRR vs. Frequency
30033866
Supply Current vs. Supply Voltage
30033812
Sinking Current vs. Supply Voltage
30033813
Sourcing Current vs. Supply Voltage
30033814
11 www.national.com
LMP2231 Single
Output Swing High vs. Supply Voltage
30033815
Output Swing Low vs. Supply Voltage
30033816
Open Loop Frequency Response
30033821
Open Loop Frequency Response
30033822
Phase Margin vs. Capacitive Load
30033863
Slew Rate vs. Supply Voltage
30033830
www.national.com 12
LMP2231 Single
THD+N vs. Amplitude
30033828
THD+N vs. Frequency
30033829
Large Signal Step Response
30033824
Small Signal Step Response
30033823
Large Signal Step Response
30033826
Small Signal Step Response
30033825
13 www.national.com
LMP2231 Single
CMRR vs. Frequency
30033867
Input Voltage Noise vs. Frequency
30033819
www.national.com 14
LMP2231 Single
Application Information
LMP2231
The LMP2231 is a single CMOS precision amplifier that offer
low offset voltage and low offset voltage drift, and high gain
while only consuming 10 μA of current per channel.
The LMP2231 is a micropower op amp, consuming only
10 μA of current. Micropower op amps extend the run time of
battery powered systems and reduce energy consumption in
energy limited systems. The guaranteed supply voltage range
of 1.8V to 5.0V along with the ultra-low supply current extend
the battery run time in two ways. The extended guaranteed
power supply voltage range of 1.8V to 5.0V enables the op
amp to function when the battery voltage has depleted from
its nominal value down to 1.8V. In addition, the lower power
consumption increases the life of the battery.
The LMP2231 has an input referred offset voltage of only
±150 μV maximum at room temperature. This offset is guar-
anteed to be less than ±230 μV over temperature. This mini-
mal offset voltage along with very low TCVOS of only
0.3 µV/°C typical allows more accurate signal detection and
amplification in precision applications.
The low input bias current of only ±20 fA gives the LMP2231
superiority for use in high impedance sensor applications.
Bias Current of an amplifier flows through source resistance
of the sensor and the voltage resulting from this current flow
appears as a noise voltage on the input of the amplifier. The
low input bias current enables the LMP2231 to interface with
high impedance sensors while generating negligible voltage
noise. Thus the LMP2231 provides better signal fidelity and
a higher signal-to-noise ration when interfacing with high
impedance sensors.
National Semiconductor is heavily committed to precision
amplifiers and the market segment they serve. Technical sup-
port and extensive characterization data is available for sen-
sitive applications or applications with a constrained error
budget.
The operating supply voltage range of 1.8V to 5.5V over the
extensive temperature range of −40°C to 125°C makes the
LMP2231 an excellent choice for low voltage precision appli-
cations with extensive temperature requirements.
The LMP2231 is offered in the space saving 5-Pin SOT23 and
8-pin SOIC package. These small packages are ideal solu-
tions for area constrained PC boards and portable electron-
ics.
TOTAL NOISE CONTRIBUTION
The LMP2231 has a very low input bias current, very low input
current noise, and low input voltage noise for micropower
amplifier. As a result, this amplifier makes a great choice for
circuits with high impedance sensor applications.
Figure 1 shows the typical input noise of the LMP2231 as a
function of source resistance where:
en denotes the input referred voltage noise
ei is the voltage drop across source resistance due to input
referred current noise or ei = RS * in
et shows the thermal noise of the source resistance
eni shows the total noise on the input.
Where:
The input current noise of the LMP2231 is so low that it will
not become the dominant factor in the total noise unless
source resistance exceeds 300 M, which is an unrealisti-
cally high value. As is evident in Figure 1, at lower RS values,
total noise is dominated by the amplifier’s input voltage noise.
Once RS is larger than a 100 k, then the dominant noise
factor becomes the thermal noise of RS. As mentioned before,
the current noise will not be the dominant noise factor for any
practical application.
30033848
FIGURE 1. Total Input Noise
VOLTAGE NOISE REDUCTION
The LMP2231 has an input voltage noise of 60 nV/ . While
this value is very low for micropower amplifiers, this input
voltage noise can be further reduced by placing N amplifiers
in parallel as shown in Figure 2. The total voltage noise on the
output of this circuit is divided by the square root of the num-
ber of amplifiers used in this parallel combination. This is
because each individual amplifier acts as an independent
noise source, and the average noise of independent sources
is the quadrature sum of the independent sources divided by
the number of sources. For N identical amplifiers, this means:
15 www.national.com
LMP2231 Single