August 1999
LMC2001
High Precision, 6MHz Rail-To-Rail Output Operational
Amplifier
LMC2001 High Precision, 6MHz Rail-To-Rail Output Operational Amplifier
General Description
The LMC2001 is a new precision amplifier that offers unprecedented accuracy and stability at an affordable price
and is offered in miniature (SOT23-5) package. This device
utilizes patented techniques to measure and continually correct the input offset error voltage. The result is an amplifier
which is ultra stableovertime,andtemperature.It has excellent CMRR and PSRR ratings, and does not exhibit the familiar 1/f voltage and current noise increase that plagues traditional amplifiers. The combination of the LMC2001
characteristics makes it a good choice for transducer amplifiers, high gain configurations, ADC buffer amplifiers, DAC
I-V conversion, and any other 5V application requiring precision and/or stability.
Other useful benefits of the LMC2001 are rail-to-rail output,
low supply current of 750µA, and wide gain-bandwidth
product of 6MHz. The LMC2001 comes in 5 pin SOT23 and
8 pin SOIC. These extremely versatile features found in the
LMC2001 provide high performance and ease of use.
Connection Diagrams
8-Pin SO
DS100058-1
Top View
Features
(Vs=5V,RL= 10K to V+/2, Typ. Unless Noted)
n Low Guaranteed V
n e
With No 1/f 85nV/
n
n High CMRR 120dB
n High PSRR 120dB
n High A
VOL
n Wide Gain-Bandwidth Product 6MHz
n High Slew Rate 5V/µs
n Low Supply Current 750µA
n Rail-To-Rail Output 30mV from either rail
n No External Capacitors Required
os
40µV
137dB
Applications
n Precision Instrumentation Amplifiers
n Thermocouple Amplifiers
n Strain Gauge Bridge Amplifier
5-Pin SOT23
DS100058-2
Top View
Ordering Information
Package Temperature Range Package
Commercial
0˚C to +70˚C
8-pin Small Outline LMC2001AIM LMC2001AIM Rails M08A
5-pin SOT23-5 LMC2001ACM5 A09A 1k Units Tape
LMC2001ACM5X 3k Units Tape
© 1999 National Semiconductor Corporation DS100058 www.national.com
Industrial
−40˚C to +85˚C
LMC2001AIMX 2.5k Units Tape
Marking
Transport
Media
and Reel
and Reel
and Reel
NSC
Drawing
MA05B
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 2500V
Machine Model 150V
Differential Input Voltage
Supply Voltage (V
+-V-
) 5.6V
Current At Input Pin 30mA
Current At Output Pin 30mA
Current At Power Supply Pin
(Note 3)
±
Supply Voltage
50mA
Storage Temperature Range -65˚C to 150˚C
Junction Temperature (T
(Note 4)
)
J
150˚C
Operating Ratings (Note 1)
Supply voltage 4.75V to 5.25V
Temperature Range
LMC2001AI -40˚C ≤ T
LMC2001AC 0˚C ≤ T
Thermal resistance ( θ
)
JA
M Package, 8-pin Surface Mount 180˚C /W
M5 Package, SOT23-5 274˚C /W
≤ 85˚C
J
≤ 70˚C
J
Lead Temperature (soldering, 10
260˚C
sec)
DC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ= 25˚C, V+= 5V, V-= 0V, VCM= 2.5V, VO= 2.5V and R
Boldface limits apply at the temperature extremes.
Symbol Parameter Conditions
V
OS
Input Offset Voltage (Note 11) 0.5 40
Offset Calibration Time 5 30 ms
TCV
Input Offset Voltage (Note 12) 0.015 µV/˚C
OS
Long-Term Offset Drift (Note 8) 0.006 µV/month
Lifetime V
I
IN
I
OS
R
IND
Input Current (Note 9) -3 pA
Input Offset Current 6 pA
Input Differential Resistance 9 MΩ
CMRR Common Mode Rejection
Ratio
PSRR Power Supply
drift (Note 8) 2.5 5 µV Max
OS
0V ≤ V
CM
0.1V ≤ V
CM
4.75V ≤ V
Rejection Ratio
A
VOL
V
O
I
O
Large Signal Voltage Gain
(Note 7)
Output Swing R
Output Current Sourcing, VO=0V
RL= 10kΩ 137 105
=2kΩ 128 95
R
L
=
10kΩ to 2.5V
L
=
(diff)
V
IN
=
R
2kΩ to 2.5V
L
=
(diff)
V
IN
(diff) =±0.5V
V
IN
Sinking, V
(diff) =±0.5V
V
I
S
Supply Current 0.75 1.0
IN
Typ
(Note 5)
≤ 3.5V 120 100 dB
≤ 3.5V 110 90 dB
+
≤ 5.25V 120 95
4.975 4.955
±
0.5V
0.030 0.060
4.936 V
±
0.5V
0.075 V
5.9 4.1
O
=5V
14.5 4.5
Limit(Note 6)
60
90
100
90
4.955
0.060
1.5
1.5
1.2
>
1MΩ.
L
Units
µV
max
min
min
dB
min
dB
min
V
min
V
max
mA
min
mA
min
mA
max
www.national.com 2
AC Electrical Characteristics
TJ= 25˚C, V+= 5V, V-= 0V, VCM= 2.5V, VO= 2.5V, and R
Symbol Parameter Conditions
SR Slew Rate A
= +1, Vin=3.5Vpp 5 V/µs
V
GBW Gain-Bandwidth Product 6 MHz
θ
G
e
n
Phase Margin 75 Deg
m
Gain Margin 12 dB
m
Input-Referred Voltage Noise f = 0.1Hz 85 nV/
enp-p Input-Referred Voltage Noise RS= 100Ω, DC to 10Hz 1.6 µVpp
i
n
Input-Referred Current Noise f = 0.1Hz 180 fA/
>
1MΩ.
L
Typ
(Note 5)
Units
THD Total Harmonic Distortion f = 1kHz, Av = -2
= 10kΩ,VO= 4.5Vpp
R
L
0.02
trec Input Overload Recovery Time 50 ms
T
S
Output Settling time (Note 10) A
(Note 10)A
Note 1: 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 guaranteed. For guaranteed specifications and test conditions, see the Electrical Characteristics.
Note 2: Human body model, 1.5kΩ in series with 100pF. Machine model, 200Ω in series with 100pF.
Note 3: Output currents in excess of
Note 4: The maximum power dissipation is a function of T
-TA)/θJA. All numbers apply for packages soldered directly onto a PC board.
Note 5: Typical values represent the most likely parametric norm.
Note 6: All limits are guaranteed by testing or statistical analysis, unless otherwise noted.
+
Note 7: V
=5V,VCM= 2.5V, and RLconnected to 2.5V. For Sourcing tests, 2.5V ≤ VO≤ 4.8V. For Sinking tests, 0.2V ≤ VO≤ 2.5V.
Note 8: Guaranteed Vos Drift is based on 280 devices operated for 1000 hrs at 150˚C (equivalent to 30 years 55ºC).
Note 9: Guaranteed by design only.
Note 10: Settling times shown correspond to the worse case (positive or negative step) and does not include slew time. See the Application Note section for test
schematic.
Note 11: The limits are set by the accuracy of high speed automatic test equipment. For the typical V
Note 12: Precision bench measurement of more than 300 units. More than 65%of units had less than 15nV /˚C V
±
30mA over long term may adversely affect reliability.
=
+1, 1V step 1
V
=
−1, 1V step 1
V
, θJA, and TA. The maximum allowable power dissipation at any ambient temperature is PD=(T
J(max)
%
%
0.1
%
0.01
%
%
0.1
%
0.01
distribution, see the curve on page 4.
OS
OS
250 ns
400
3200
80
860
1400
J(max)
drift.
%
www.national.com3
Typical Performance Characteristics
=
T
A
25C, V
=
5V unless otherwise specified.
S
Distribution
V
OS
VOSvs V
S
VOSvs V
CM
+IINvs V
CMR vs V
+
V
vs V
OUT
CM
CM
S
DS100058-63
DS100058-68
DS100058-92
DS100058-91
−IINvs V
CM
DS100058-A4
CMR vs Frequency
DS100058-65
+
V
vs V
OUT
S
DS100058-97
eNvs Frequency
PSR vs Frequency
DS100058-66
−
V
vs V
OUT
S
DS100058-A0
DS100058-89
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DS100058-88
DS100058-99
Typical Performance Characteristics (Continued)
−
vs V
V
OUT
S
Gain-Phase vs V
S
Gain-Phase vs Temp
Gain-Phase vs R
THD+N vs V
OUT
DS100058-98
L
DS100058-50
DS100058-76
Gain-Phase vs C
Isource vs V
LOAD
OUT
DS100058-49
DS100058-47
DS100058-A7
THD+N vs Frequency
DS100058-A5
Isink vs V
OUT
DS100058-A8
DS100058-48
Isupply vs V
S
DS100058-96
www.national.com5
Application Notes
The Benefits of LMC2001
No 1/f Noise
Using patented methods, the LMC2001 eliminates the 1/f
noise present in other amplifiers. This noise which increases
as frequency decreases is a major source of measurement
error in all DC coupled measurements. Low frequency noise
appears as a constantly changing signal in series with any
measurement being made. As a result, even when the measurement is made rapidly, this constantly changing noise signal will corrupt the result. The value of this noise signal can
be surprisingly large. For example: If a conventional amplifier has a high frequency noise level of 10nV/
noise corner of 10 Hz, the RMS noise at 0.001 Hz is 1µV/
This is equivalent to a 6µV peak-to-peak error. In a circuit
with a gain of 1000, this produces a 6mV peak-to-peak output error. This number of 0.001 Hz might appear unreasonably low but when a data acquisition system is operating for
17 minutes it has been on long enough to include this error.
In this same time, the LMC2001 will only have a 0.51mV output error. This is more than 13.3 times less error.
Keep in mind that this 1/f error gets even larger at lower frequencies.
At the extreme, many people try to reduce this error by integrating or taking several samples of the same signal. This is
also doomed to failure because the 1/f nature of this noise
means that taking longer samples just moves the measurement into lower frequencies where the noise level is even
higher.
The LMC2001 eliminates this source of error.The noise level
is constant with frequency so that reducing the bandwidth reduces the errors caused by noise.
Another source of error that is rarely mentioned is the error
voltages caused by the inadvertent thermocouples created
when the common “Kovar type” package lead materials are
soldered to a copper printed circuit board. These steel based
leadframe materials can produce over 35uV/˚C when soldered onto a copper trace. This can result in thermocouple
noise that is equal to the LMC2001 noise when there is a
temperature difference of only 0.0014˚C between the lead
and the board!
For this reason, the leadframe of the LMC2001 is made of
copper. This results in equal and opposite junctions which
cancel this effect. The extremely small size of the SOT-23
package results in the leads being very close together. This
further reduces the probability of temperature differences
and hence decreases thermal noise.
Overload Recovery
The LMC2001 recovers from input overload much faster
than most chopper stabilized opamps. Recovery, from driving the amplifier to 2X the full scale output, only requires
about 50ms. Most chopper stabilized amplifiers will take
from 250ms to several seconds to recover from this same
overload. This is because large capacitors are used to store
the unadjusted offset voltage.
The wide bandwidth of the LMC2001 enhances performance
when it is used as an amplifier to drive loads that inject transients back into the output. A to Ds and multiplexers are examples of this type of load. To simulate this type of load, a
pulse generator producing a 1V peak square wave was connected to the output through a 10pF capacitor. (
The typical time for the output to recover to 1%of the applied
and a
Figure 1
pulse is 80ns. To recover to 0.1%requires 860ns. This rapid
recovery is due to the wide bandwidth of the output stage
and large total GBW.
DS100058-B0
FIGURE 1.
No External Capacitors Required
The LMC2001 does not need external capacitors. This eliminates the problems caused by capacitor leakage and dielectric absorption, which can cause delays of several seconds
from turn-on until the amplifier is settled.
More Benefits
The LMC2001 offers the benefits mentioned above and
more. It is rail-to-rail output and consumes only 750µA of
supply current while providing excellent DC andAC electrical
performance. In DC performance, the LMC2001 achieves
120dB of CMRR, 120dB of PSRR and 137dB of open loop
gain. In AC performance, the LMC2001 provides 6MHz of
gain-bandwidth product and 5V/µs of slew rate.
How the LMC2001 Works
The LMC2001 uses new, patented techniques to achieve the
high DC accuracy traditionally associated with chopper stabilized amplifiers without the major drawbacks produced by
chopping. The LMC2001 continuously monitors the input offset and corrects this error. The conventional chopping process produces many mixing products, both sums and differences, between the chopping frequency and the incoming
signal frequency. This mixing causes large amounts of distortion, particularly when the signal frequency approaches
the chopping frequency. Even without an incoming signal,
the chopper harmonics mix with each other to produce even
more trash. If this sounds unlikely or difficult to understand,
look at the plot (
Figure 2
), of the output of a typical (MAX432)
chopper stabilized opamp. This is the output when there is
no incoming signal, just the amplifier in a gain of -10 with the
input grounded. The chopper is operating at about 150Hz,
the rest is mixing products. Add an input signal and the mess
gets much worse. Compare this plot with
LMC2001. This data was taken under the exact same conditions. The auto zero action is visible at about 11kHz but note
the absence of mixing products at other frequencies.As a result, the LMC2001 has very low distortion of 0.02%and very
low mixing products.
Input Currents
The LMC2001 input current is different than standard bipolar
or CMOS input currents in that it appears as a current flowing in one input and out the other. Under most operating conditions, these currents are in the picoamp level and will have
little or no effect in most circuits. These currents increase to
the nA level when the common-mode voltage is near the minus supply. (see the typical curves) At high temperatures
such as 85˚C, the input currents become larger, 0.5nA typical, and are both positive except when the Vcm is near V
operation is expected at low common-mode voltages and
high temperature, do not add resistance in series with the inputs to balance the impedances. Doing this can cause an in-
)
crease in offset voltage.
Figure 3
of the
−
.If
www.national.com 6
Application Notes (Continued)
FIGURE 2.
eration). Higher closed loop gains are also possible with a
corresponding reduction in realizable bandwidth. Table 1
shows some other closed loop gain possibilities along with
the measured performance in each case
Application Circuits
DS100058-A1
DS100058-21
FIGURE 4. Single Supply Strain- Gauge Amplifier
DS100058-A0
FIGURE 3.
Figure 4
This Strain-Gauge (
) amplifier provides high gain
(1006 or 60 dB) with very low offset and drift. Using the resistors tolerance as shown, the worst case CMRR will be
greater than 90 dB. The common-mode gain is directly related to the resistor mismatch and is independent of the differential gain that is set by R3. The worst case commonmode gain is −54 dB. This gain becomes even lower,
improving CMRR, if the resistor ratio matching is improved.
Extending Supply Voltages and Output Swing by Using
a Composite Amplifier Configuration:
In cases where substantially higher output swing is required
with higher supply voltages, arrangements like the ones
shown in
Figure 5
, and
Figure 6
could be used (pin numbers
shown are for SO-8 package). These configurations utilize
the excellent DC performance of the LMC2001 while at the
same time allow the superior voltage and frequency capabilities of the LM6171 to set the dynamic performance of the
overall amplifier. For example, it is possible to achieve
±
12V
output swing with 300MHz of overall GBW (Av=100) while
keeping the worst case output shift due to Vos less than
4mV.The LMC2001 output voltage is kept at about mid-point
of it’s overall supply voltage and it’s input common mode
voltage range allows the V
case (
Figure 5
, inverting operation) and tied to a small non-
critical negative bias in another (
-
terminal to be grounded in one
Figure 6
, non-inverting op-
DS100058-30
FIGURE 5. Inverting Composite Amplifier
www.national.com7
Application Notes (Continued)
DS100058-31
FIGURE 6. Non-Inverting Composite Amplifier
TABLE 1. Composite Amplifier Measured Performance
Av R1 R2 C2 BW SR e
(ohm) (ohm) (pF) (MHz) (V/us) (mVpp)
50 200 10K 8 3.3 178 37
100 100 10K 10 2.5 174 70
100 1K 100K 0.67 3.1 170 70
500 200 100K 1.75 1.4 96 250
1000 100 100K 2.2 0.98 64 400
In terms of the measured output peak-to-peak noise, the following relationship holds between output noise voltage, e
for different closed loop gain, A
width is BW:
, settings, where -3dB Band-
v
It should be kept in mind that in order to minimize the output
noise voltage for a given closed loop gain setting, one could
npp
npp
(1)
minimize the overall bandwidth. As can be seen from Equation 1 above, the improvement in output noise has a square
law relationship to the reduction in BW.
In the case of the inverting configuration, it is also possible to
increase the input impedance of the overall amplifier, by raising the value of R1, without having to increase the feedback
resistor, R2, to impractical values, by utilizing a “T” network
as feedback. See the LMC6442 data sheet (Application
Notes section) for more details on this.
LMC2001 as ADC Input Amplifier
The LMC2001 is a great choice for an amplifier stage immediately before the input of an A/D converter (AC or DC
coupled) see
Figure 7
and
Figure 8
because of the following
important characteristics:
a) Very low offset voltage and offset voltage drift over time
and temperature allow a high closed loop gain setting without introducing any short term or long term errors. For example, when set to a closed loop gain of 100 as the analog
input amplifier of a 12 bit A/D converter, the overall conversion error over full operation temperature and 30 years life of
the part (operating at 50˚C) would be less than 5LSB.
b) Fast large signal settling time to 0.01%of final value (1.4
us) allows 12 bit accuracy at 100KHz or more sampling rate.
c) No flicker (1/f) noise means unsurpassed data accuracy
over any measurement period of time, no matter how long.
Consider the following opamp performance, based on a typical commercially available device, for comparison:
Opamp flatband noise 8nV/
0.94
1/f
corner frequency 100Hz
f(max) 100Hz
Av 100
Measurement time 100 sec
The example above, will result in about 3mVpp (2.5LSB) of
output noise contribution due to the opamp alone, compared
to about 420 uVpp (less than 1LSB) when that opamp is re-
,
placed with the LMC2001 which has no 1/f contribution. If the
measurement time is increased from 100 sec. to 1 hr., the
improvement realized by using the LMC2001 would be a factor of about 44 times (18.5mVpp compared to 420uV when
LMC2001 is used) mainly because the LMC2001 accuracy is
not compromised by increasing the observation time.
d) Copper lead frame construction minimizes any thermocouple effects which would degrade low level/high gain data
conversion application accuracy (see discussion under “The
Benefits of the LMC2001” section above).
e) Rail-to-Rail output swing maximized the ADC dynamic
range in 5V single supply converter applications. Below are
some typical block diagrams showing the LMC2001 used as
an ADC amplifier (
Figure 7
and
Figure 8
).
www.national.com 8
Application Notes (Continued)
DS100058-52
FIGURE 7.
DS100058-53
FIGURE 8.
www.national.com9
Physical Dimensions inches (millimeters) unless otherwise noted
M08A
www.national.com 10
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
LMC2001 High Precision, 6MHz Rail-To-Rail Output Operational Amplifier
MA05B
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www.national.com
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