LMC6482
LMC6482 CMOS Dual Rail-To-Rail Input and Output Operational Amplifier
Literature Number: SNOS674C
LMC6482
CMOS Dual Rail-To-Rail Input and Output Operational
Amplifier
General Description
The LMC6482 provides a common-mode range that extends
to both supply rails. This rail-to-rail performance combined
with excellent accuracy, due to a high CMRR, makes it
unique among rail-to-rail input amplifiers.
It is ideal for systems, such as data acquisition, that require
a large input signal range. The LMC6482 is also an excellent
upgrade for circuits using limited common-mode range am-
plifiers such as the TLC272 and TLC277.
Maximum dynamic signal range is assured in low voltage
and single supply systems by the LMC6482’s rail-to-rail out-
put swing. The LMC6482’s rail-to-rail output swing is guar-
anteed for loads down to 600Ω.
Guaranteed low voltage characteristics and low power dis-
sipation make the LMC6482 especially well-suited for
battery-operated systems.
LMC6482 is also available in MSOP package which is al-
most half the size of a SO-8 device.
See the LMC6484 data sheet for a Quad CMOS operational
amplifier with these same features.
Features
(Typical unless otherwise noted)
nRail-to-Rail Input Common-Mode Voltage Range
(Guaranteed Over Temperature)
nRail-to-Rail Output Swing (within 20mV of supply rail,
100kΩload)
nGuaranteed 3V, 5V and 15V Performance
nExcellent CMRR and PSRR: 82dB
nUltra Low Input Current: 20fA
nHigh Voltage Gain (R
L
= 500kΩ): 130dB
nSpecified for 2kΩand 600Ωloads
nAvailable in MSOP Package
Applications
nData Acquisition Systems
nTransducer Amplifiers
nHand-held Analytic Instruments
nMedical Instrumentation
nActive Filter, Peak Detector, Sample and Hold, pH
Meter, Current Source
nImproved Replacement for TLC272, TLC277
3V Single Supply Buffer Circuit
Rail-To-Rail Input Rail-To-Rail Output
01171301 01171302
01171303
Connection Diagram
01171304
September 2003
LMC6482 CMOS Dual Rail-To-Rail Input and Output Operational Amplifier
© 2004 National Semiconductor Corporation DS011713 www.national.com
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) 1.5kV
Differential Input Voltage ±Supply Voltage
Voltage at Input/Output Pin (V
+
) +0.3V, (V
−
) −0.3V
Supply Voltage (V
+
−V
−
) 16V
Current at Input Pin (Note 12) ±5mA
Current at Output Pin
(Notes 3, 8) ±30mA
Current at Power Supply Pin 40mA
Lead Temperature
(Soldering, 10 sec.) 260˚C
Storage Temperature Range −65˚C to +150˚C
Junction Temperature (Note 4) 150˚C
Operating Ratings (Note 1)
Supply Voltage 3.0V ≤V+ ≤15.5V
Junction Temperature Range
LMC6482AM −55˚C ≤T
J
≤
+125˚C
LMC6482AI, LMC6482I −40˚C ≤T
J
≤+85˚C
Thermal Resistance (θ
JA
)
N Package, 8-Pin Molded DIP 90˚C/W
M Package, 8-Pin Surface
Mount 155˚C/W
MSOP package, 8-Pin Mini SO 194˚C/W
DC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for T
J
= 25˚C, V
+
= 5V, V
−
= 0V, V
CM
=V
O
=V
+
/2 and R
L
>1M. Boldface
limits apply at the temperature extremes.
Symbol Parameter Conditions Typ
(Note 5)
LMC6482AI LMC6482I LMC6482M Units
Limit Limit Limit
(Note 6) (Note 6) (Note 6)
V
OS
Input Offset Voltage 0.11 0.750 3.0 3.0 mV
1.35 3.7 3.8 max
TCV
OS
Input Offset Voltage 1.0 µV/˚C
Average Drift
I
B
Input Current (Note 13) 0.02 4.0 4.0 10.0 pA
max
I
OS
Input Offset Current (Note 13) 0.01 2.0 2.0 5.0 pA
max
C
IN
Common-Mode 3 pF
Input Capacitance
R
IN
Input Resistance >10 TeraΩ
CMRR Common Mode 0V ≤V
CM
≤15.0V 82 70 65 65 dB
min
Rejection Ratio V
+
= 15V 67 62 60
0V ≤V
CM
≤5.0V 82 70 65 65
V
+
=5V 67 62 60
+PSRR Positive Power Supply 5V ≤V
+
≤15V, V
−
=0V82706565dB
Rejection Ratio V
O
= 2.5V 67 62 60 min
−PSRR Negative Power Supply −5V ≤V
−
≤−15V, V
+
=0V82706565dB
Rejection Ratio V
O
= −2.5V 67 62 60 min
V
CM
Input Common-Mode V
+
= 5V and 15V V
−
− 0.3 − 0.25 − 0.25 − 0.25 V
Voltage Range For CMRR ≥50dB 000max
V
+
+ 0.3V V
+
+ 0.25 V
+
+ 0.25 V
+
+ 0.25 V
V
+
V
+
V
+
min
A
V
Large Signal R
L
=2kΩSourcing 666 140 120 120 V/mV
Voltage Gain (Notes 7, 13) 84 72 60 min
Sinking 75 35 35 35 V/mV
20 20 18 min
R
L
= 600ΩSourcing 300 80 50 50 V/mV
(Notes 7, 13) 48 30 25 min
Sinking 35 20 15 15 V/mV
LMC6482
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DC Electrical Characteristics (Continued)
Unless otherwise specified, all limits guaranteed for T
J
= 25˚C, V
+
= 5V, V
−
= 0V, V
CM
=V
O
=V
+
/2 and R
L
>1M. Boldface
limits apply at the temperature extremes.
Symbol Parameter Conditions Typ
(Note 5)
LMC6482AI LMC6482I LMC6482M Units
Limit Limit Limit
(Note 6) (Note 6) (Note 6)
13 10 8 min
V
O
Output Swing V
+
= 5V 4.9 4.8 4.8 4.8 V
R
L
=2kΩto V
+
/2 4.7 4.7 4.7 min
0.1 0.18 0.18 0.18 V
0.24 0.24 0.24 max
V
+
= 5V 4.7 4.5 4.5 4.5 V
R
L
= 600Ωto V
+
/2 4.24 4.24 4.24 min
0.3 0.5 0.5 0.5 V
0.65 0.65 0.65 max
V
+
= 15V 14.7 14.4 14.4 14.4 V
R
L
=2kΩto V
+
/2 14.2 14.2 14.2 min
0.16 0.32 0.32 0.32 V
0.45 0.45 0.45 max
V
+
= 15V 14.1 13.4 13.4 13.4 V
R
L
= 600Ωto V
+
/2 13.0 13.0 13.0 min
0.5 1.0 1.0 1.0 V
1.3 1.3 1.3 max
I
SC
Output Short Circuit Sourcing, V
O
=0V 20161616mA
Current 12 12 10 min
V
+
= 5V Sinking, V
O
=5V 15111111mA
9.5 9.5 8.0 min
I
SC
Output Short Circuit Sourcing, V
O
=0V 30282828mA
Current 22 22 20 min
V
+
= 15V Sinking, V
O
= 12V 30 30 30 30 mA
(Note 8) 24 24 22 min
I
S
Supply Current Both Amplifiers 1.0 1.4 1.4 1.4 mA
V
+
= +5V, V
O
=V
+
/2 1.8 1.8 1.9 max
Both Amplifiers 1.3 1.6 1.6 1.6 mA
V
+
= 15V, V
O
=V
+
/2 1.9 1.9 2.0 max
AC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for T
J
= 25˚C, V
+
= 5V, V
−
= 0V, V
CM
=V
O
=V
+
/2, and R
L
>1M. Boldface
limits apply at the temperature extremes.
Symbol Parameter Conditions Typ
(Note 5)
LMC6482AI LMC6482I LMC6482M Units
Limit Limit Limit
(Note 6) (Note 6) (Note 6)
SR Slew Rate (Note 9) 1.3 1.0 0.9 0.9 V/µs
0.7 0.63 0.54 min
GBW Gain-Bandwidth Product V
+
= 15V 1.5 MHz
φ
m
Phase Margin 50 Deg
G
m
Gain Margin 15 dB
Amp-to-Amp Isolation (Note 10) 150 dB
e
n
Input-Referred F = 1kHz 37 nV/√Hz
Voltage Noise V
cm
=1V
i
n
Input-Referred F = 1kHz 0.03 pA/√Hz
Current Noise
LMC6482
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AC Electrical Characteristics (Continued)
Unless otherwise specified, all limits guaranteed for T
J
= 25˚C, V
+
= 5V, V
−
= 0V, V
CM
=V
O
=V
+
/2, and R
L
>1M. Boldface
limits apply at the temperature extremes.
Symbol Parameter Conditions Typ
(Note 5)
LMC6482AI LMC6482I LMC6482M Units
Limit Limit Limit
(Note 6) (Note 6) (Note 6)
T.H.D. Total Harmonic Distortion F = 10kHz, A
V
=−2 %
R
L
= 10kΩ,V
O
= 4.1 V
PP
0.01
F = 10kHz, A
V
=−2
R
L
= 10kΩ,V
O
= 8.5 V
PP
0.01 %
V
+
= 10V
DC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for T
J
= 25˚C, V
+
= 3V, V
−
= 0V, V
CM
=V
O
=V
+
/2 and R
L
>1M.
Symbol Parameter Conditions Typ
(Note 5)
LMC6482AI LMC6482I LMC6482M Units
Limit Limit Limit
(Note 6) (Note 6) (Note 6)
V
OS
Input Offset Voltage 0.9 2.0 3.0 3.0 mV
2.7 3.7 3.8 max
TCV
OS
Input Offset Voltage 2.0 µV/˚C
Average Drift
I
B
Input Bias Current 0.02 pA
I
OS
Input Offset Current 0.01 pA
CMRR Common Mode 0V ≤V
CM
≤3V 74 64 60 60 dB
Rejection Ratio min
PSRR Power Supply 3V ≤V
+
≤15V, V
−
=0V80686060dB
Rejection Ratio min
V
CM
Input Common-Mode For CMRR ≥50dB V
−
−0.25 0 0 0 V
Voltage Range max
V
+
+ 0.25 V
+
V
+
V
+
V
min
V
O
Output Swing R
L
=2kΩto V
+
/2 2.8 V
0.2 V
R
L
= 600Ωto V
+
/2 2.7 2.5 2.5 2.5 V
min
0.37 0.6 0.6 0.6 V
max
I
S
Supply Current Both Amplifiers 0.825 1.2 1.2 1.2 mA
1.5 1.5 1.6 max
AC Electrical Characteristics
Unless otherwise specified, V
+
= 3V, V
−
= 0V, V
CM
=V
O
=V
+
/2, and R
L
>1M.
Symbol Parameter Conditions Typ
(Note 5)
LMC6482AI LMC6482I LMC6482M Units
Limit Limit Limit
(Note 6) (Note 6) (Note 6)
SR Slew Rate (Note 11) 0.9 V/µs
GBW Gain-Bandwidth Product 1.0 MHz
T.H.D. Total Harmonic Distortion F = 10kHz, A
V
= −2 0.01 %
R
L
= 10kΩ,V
O
=2V
PP
Note 1: Absolute Maximum Ratings indicate limts 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 the test conditions, see the Electrical Characteristics.
Note 2: Human body model, 1.5kΩin series with 100pF. All pins rated per method 3015.6 of MIL-STD-883. This is a Class 1 device rating.
LMC6482
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AC Electrical Characteristics (Continued)
Note 3: Applies to both single-supply and split-supply operation. Continuous short circuit operation at elevated ambient temperature can result in exceeding the
maximum allowed junction temperature of 150˚C. Output currents in excess of ±30mA over long term may adversely affect reliability.
Note 4: The maximum power dissipation is a function of TJ(max),θJA, and TA. The maximum allowable power dissipation at any ambient temperature is PD=(T
J(max)
−T
A)/θJA. All numbers apply for packages soldered directly into a PC board.
Note 5: Typical Values represent the most likely parametric norm.
Note 6: All limits are guaranteed by testing or statistical analysis.
Note 7: V+= 15V, VCM = 7.5V and RLconnected to 7.5V. For Sourcing tests, 7.5V ≤VO≤11.5V. For Sinking tests, 3.5V ≤VO≤7.5V.
Note 8: Do not short circuit output to V+, when V+is greater than 13V or reliability will be adversely affected.
Note 9: V+= 15V. Connected as Voltage Follower with 10V step input. Number specified is the slower of either the positive or negative slew rates.
Note 10: Input referred, V+= 15V and RL= 100 kΩconnected to 7.5V. Each amp excited in turn with 1 kHz to produce VO=12V
PP.
Note 11: Connected as voltage Follower with 2V step input. Number specified is the slower of either the positive or negative slew rates.
Note 12: Limiting input pin current is only necessary for input voltages that exceed absolute maximum input voltage ratings.
Note 13: Guaranteed limits are dictated by tester limitations and not device performance. Actual performance is reflected in the typical value.
Note 14: For guaranteed Military Temperature parameters see RETS6482X.
Typical Performance Characteristics
V
S
= +15V, Single Supply, T
A
= 25˚C unless otherwise
specified
Supply Current vs. Supply Voltage Input Current vs. Temperature
01171340 01171341
Sourcing Current vs. Output Voltage Sourcing Current vs. Output Voltage
01171342 01171343
LMC6482
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Typical Performance Characteristics V
S
= +15V, Single Supply, T
A
= 25˚C unless otherwise
specified (Continued)
Sourcing Current vs. Output Voltage Sinking Current vs. Output Voltage
01171344 01171345
Sinking Current vs. Output Voltage Sinking Current vs. Output Voltage
01171346 01171347
Output Voltage Swing vs. Supply Voltage Input Voltage Noise vs. Frequency
01171348
01171349
LMC6482
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Typical Performance Characteristics V
S
= +15V, Single Supply, T
A
= 25˚C unless otherwise
specified (Continued)
Input Voltage Noise vs. Input Voltage Input Voltage Noise vs. Input Voltage
01171350 01171351
Input Voltage Noise vs. Input Voltage Crosstalk Rejection vs. Frequency
01171352 01171353
Crosstalk Rejection vs. Frequency Positive PSRR vs. Frequency
01171354 01171355
LMC6482
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Typical Performance Characteristics V
S
= +15V, Single Supply, T
A
= 25˚C unless otherwise
specified (Continued)
Negative PSRR vs. Frequency CMRR vs. Frequency
01171356 01171357
CMRR vs. Input Voltage CMRR vs. Input Voltage
01171358 01171359
CMRR vs. Input Voltage ∆V
OS
vs. CMR
01171360 01171361
LMC6482
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Typical Performance Characteristics V
S
= +15V, Single Supply, T
A
= 25˚C unless otherwise
specified (Continued)
∆V
OS
vs. CMR Input Voltage vs. Output Voltage
01171362 01171363
Input Voltage vs. Output Voltage Open Loop Frequency Response
01171364 01171365
Open Loop Frequency Responce Open Loop Frequency Response vs. Temperature
01171366 01171367
LMC6482
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Typical Performance Characteristics V
S
= +15V, Single Supply, T
A
= 25˚C unless otherwise
specified (Continued)
Maximum Output Swing vs. Frequency Gain and Phase vs. Capacitive Load
01171368 01171369
Gain and Phase vs. Capacitive Load Open Loop Output Impedance vs. Frequency
01171370 01171371
Open Loop Output Impedance vs. Frequency Slew Rate vs. Supply Voltage
01171372 01171373
LMC6482
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Typical Performance Characteristics V
S
= +15V, Single Supply, T
A
= 25˚C unless otherwise
specified (Continued)
Non-Inverting Large Signal Pulse Response Non-Inverting Large Signal Pulse Response
01171374 01171375
Non-Inverting Large Signal Pulse Response Non-Inverting Small Signal Pulse Response
01171376 01171377
Non-Inverting Small Signal Pulse Response Non-Inverting Small Signal Pulse Response
01171378 01171379
LMC6482
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Typical Performance Characteristics V
S
= +15V, Single Supply, T
A
= 25˚C unless otherwise
specified (Continued)
Inverting Large Signal Pulse Response Inverting Large Signal Pulse Response
01171380 01171381
Inverting Large Signal Pulse Response Inverting Small Signal Pulse Response
01171382 01171383
Inverting Small Signal Pulse Response Inverting Small Signal Pulse Response
01171384 01171385
LMC6482
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Typical Performance Characteristics V
S
= +15V, Single Supply, T
A
= 25˚C unless otherwise
specified (Continued)
Stability vs. Capacitive Load Stability vs. Capacitive Load
01171386 01171387
Stability vs. Capacitive Load Stability vs. Capacitive Load
01171388 01171389
Stability vs. Capacitive Load Stability vs. Capacitive Load
01171390 01171391
LMC6482
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Application Information
1.0 AMPLIFIER TOPOLOGY
The LMC6482 incorporates specially designed wide-
compliance range current mirrors and the body effect to
extend input common mode range to each supply rail.
Complementary paralleled differential input stages, like the
type used in other CMOS and bipolar rail-to-rail input ampli-
fiers, were not used because of their inherent accuracy
problems due to CMRR, cross-over distortion, and open-
loop gain variation.
The LMC6482’s input stage design is complemented by an
output stage capable of rail-to-rail output swing even when
driving a large load. Rail-to-rail output swing is obtained by
taking the output directly from the internal integrator instead
of an output buffer stage.
2.0 INPUT COMMON-MODE VOLTAGE RANGE
Unlike Bi-FET amplifier designs, the LMC6482 does not
exhibit phase inversion when an input voltage exceeds the
negative supply voltage. Figure 1 shows an input voltage
exceeding both supplies with no resulting phase inversion on
the output.
The absolute maximum input voltage is 300mV beyond ei-
ther supply rail at room temperature. Voltages greatly ex-
ceeding this absolute maximum rating, as in Figure 2, can
cause excessive current to flow in or out of the input pins
possibly affecting reliability.
Applications that exceed this rating must externally limit the
maximum input current to ±5mA with an input resistor (R
I
)as
shown in Figure 3.
3.0 RAIL-TO-RAIL OUTPUT
The approximated output resistance of the LMC6482 is
180Ωsourcing and 130Ωsinking at V
S
= 3V and 110Ω
sourcing and 80Ωsinking at Vs = 5V. Using the calculated
output resistance, maximum output voltage swing can be
estimated as a function of load.
4.0 CAPACITIVE LOAD TOLERANCE
The LMC6482 can typically directly drive a 100pF load with
V
S
= 15V at unity gain without oscillating. The unity gain
follower is the most sensitive configuration. Direct capacitive
loading reduces the phase margin of op-amps. The combi-
nation of the op-amp’s output impedance and the capacitive
load induces phase lag. This results in either an under-
damped pulse response or oscillation.
Capacitive load compensation can be accomplished using
resistive isolation as shown in Figure 4. This simple tech-
nique is useful for isolating the capacitive inputs of multiplex-
ers and A/D converters.
01171310
FIGURE 1. An Input Voltage Signal Exceeds the
LMC6482 Power Supply Voltages with
No Output Phase Inversion
01171339
FIGURE 2. A ±7.5V Input Signal Greatly
Exceeds the 3V Supply in Figure 3 Causing
No Phase Inversion Due to R
I
01171311
FIGURE 3. R
I
Input Current Protection for
Voltages Exceeding the Supply Voltages
LMC6482
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Application Information (Continued)
Improved frequency response is achieved by indirectly driv-
ing capacitive loads, as shown in Figure 6.
R1 and C1 serve to counteract the loss of phase margin by
feeding forward the high frequency component of the output
signal back to the amplifiers inverting input, thereby preserv-
ing phase margin in the overall feedback loop. The values of
R1 and C1 are experimentally determined for the desired
pulse response. The resulting pulse response can be seen in
Figure 7.
5.0 COMPENSATING FOR INPUT CAPACITANCE
It is quite common to use large values of feedback resis-
tance with amplifiers that have ultra-low input current, like
the LMC6482. Large feedback resistors can react with small
values of input capacitance due to transducers, photo-
diodes, and circuits board parasitics to reduce phase mar-
gins.
The effect of input capacitance can be compensated for by
adding a feedback capacitor. The feedback capacitor (as in
Figure 8), C
f
, is first estimated by:
or
R
1
C
IN
≤R
2
C
f
which typically provides significant overcompensation.
Printed circuit board stray capacitance may be larger or
smaller than that of a bread-board, so the actual optimum
value for C
f
may be different. The values of C
f
should be
checked on the actual circuit. (Refer to the LMC660 quad
CMOS amplifier data sheet for a more detailed discussion.)
01171317
FIGURE 4. Resistive Isolation
of a 330pF Capacitive Load
01171318
FIGURE 5. Pulse Response of
the LMC6482 Circuit in Figure 4
01171315
FIGURE 6. LMC6482 Noninverting Amplifier,
Compensated to Handle a 330pF Capacitive Load
01171316
FIGURE 7. Pulse Response of
LMC6482 Circuit in Figure 6
01171319
FIGURE 8. Canceling the Effect of Input Capacitance
LMC6482
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Application Information (Continued)
6.0 PRINTED-CIRCUIT-BOARD LAYOUT FOR
HIGH-IMPEDANCE WORK
It is generally recognized that any circuit which must oper-
rate with less than 1000pA of leakage current requires spe-
cial layout of the PC board. When one wishes to take ad-
vantage of the ultra-low input current of the LMC6482,
typically less than 20fA, it is essential to have an excellent
layout. Fortunately, the techniques of obtaining low leakages
are quite simple. First, the user must not ignore the surface
leakage of the PC board, even through it may sometimes
appear acceptably low, because under conditions of high
humidity or dust or contamination, the surface leakage will
be appreciable.
To minimize the effect of any surface leakage, lay out a ring
of foil completely surrounding the LM6482’s inputs and the
terminals of capacitors, diodes, conductors, resistors, relay
terminals, etc. connected to the op-amp’s inputs, as in Fig-
ure 9. To have a significant effect, guard rings should be
placed on both the top and bottom of the PC board. This PC
foil must then be connected to a voltage which is at the same
voltage as the amplifier inputs, since no leakage current can
flow between two points at the same potential. For example,
a PC board trace-to-pad resistance of 10
12
Ω, which is nor-
mally considered a very large resistance, could leak 5pA if
the trace were a 5V bus adjacent to the pad of the input. This
would cause a 250 times degradation from the LMC6482’s
actual performance. However, if a guard ring is held within 5
mV of the inputs, then even a resistance of 10
11
Ωwould
cause only 0.05pA of leakage current. See Figure 10 for
typical connections of guard rings for standard op-amp con-
figurations.
The designer should be aware that when it is inappropriate
to lay out a PC board for the sake of just a few circuits, there
is another technique which is even better than a guard ring
on a PC board: Don’t insert the amplifier’s input pin into the
board at all, but bend it up in the air and use only air as an
insulator. Air is an excellent insulator. In this case you may
have to forego some of the advantages of PC board con-
struction, but the advantages are sometimes well worth the
effort of using point-to-point up-in-the-air wiring.
See Figure 11.
01171320
FIGURE 9. Example of Guard Ring in P.C. Board
Layout
01171321
Inverting Amplifier
01171322
Non-Inverting Amplifier
01171323
Follower
FIGURE 10. Typical Connections of Guard Rings
01171324
(Input pins are lifted out of PC board and soldered directly to components.
All other pins connected to PC board.)
FIGURE 11. Air Wiring
LMC6482
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Application Information (Continued)
7.0 OFFSET VOLTAGE ADJUSTMENT
Offset voltage adjustment circuits are illustrated in Figure 12
Figure 13. Large value resistances and potentiometers are
used to reduce power consumption while providing typically
±2.5mV of adjustment range, referred to the input, for both
configurations with V
S
=±5V.
8.0 UPGRADING APPLICATIONS
The LMC6484 quads and LMC6482 duals have industry
standard pin outs to retrofit existing applications. System
performance can be greatly increased by the LMC6482’s
features. The key benefit of designing in the LMC6482 is
increased linear signal range. Most op-amps have limited
input common mode ranges. Signals that exceed this range
generate a non-linear output response that persists long
after the input signal returns to the common mode range.
Linear signal range is vital in applications such as filters
where signal peaking can exceed input common mode
ranges resulting in output phase inverison or severe distor-
tion.
9.0 DATA ACQUISITION SYSTEMS
Low power, single supply data acquisition system solutions
are provided by buffering the ADC12038 with the LMC6482
(Figure 14). Capable of using the full supply range, the
LMC6482 does not require input signals to be scaled down
to meet limited common mode voltage ranges. The
LMC4282 CMRR of 82dB maintains integral linearity of a
12-bit data acquisition system to ±0.325 LSB. Other rail-to-
rail input amplifiers with only 50dB of CMRR will degrade the
accuracy of the data acquisition system to only 8 bits.
01171325
FIGURE 12. Inverting Configuration
Offset Voltage Adjustment
01171326
FIGURE 13. Non-Inverting Configuration
Offset Voltage Adjustment
LMC6482
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Application Information (Continued)
10.0 INSTRUMENTATION CIRCUITS
The LMC6482 has the high input impedance, large common-
mode range and high CMRR needed for designing instru-
mentation circuits. Instrumentation circuits designed with the
LMC6482 can reject a larger range of common-mode signals
than most in-amps. This makes instrumentation circuits de-
signed with the LMC6482 an excellent choice of noisy or
industrial environments. Other applications that benefit from
these features include analytic medical instruments, mag-
netic field detectors, gas detectors, and silicon-based
tranducers.
A small valued potentiometer is used in series with R
g
to set
the differential gain of the 3 op-amp instrumentation circuit in
Figure 15. This combination is used instead of one large
valued potentiometer to increase gain trim accuracy and
reduce error due to vibration.
01171328
FIGURE 14. Operating from the same
Supply Voltage, the LMC6482 buffers the
ADC12038 maintaining excellent accuracy
LMC6482
www.national.com 18
Application Information (Continued)
A 2 op-amp instrumentation amplifier designed for a gain of
100 is shown in Figure 16. Low sensitivity trimming is made
for offset voltage, CMRR and gain. Low cost and low power
consumption are the main advantages of this two op-amp
circuit.
Higher frequency and larger common-mode range applica-
tions are best facilitated by a three op-amp instrumentation
amplifier.
11.0 SPICE MACROMODEL
A spice macromodel is available for the LMC6482. This
model includes accurate simulation of:
•Input common-mode voltage range
•Frequency and transient response
•GBW dependence on loading conditions
•Quiescent and dynamic supply current
•Output swing dependence on loading conditions
and many more characteristics as listed on the macromodel
disk.
Contact your local National Semiconductor sales office to
obtain an operational amplifier spice model library disk.
01171329
FIGURE 15. Low Power 3 Op-Amp Instrumentation Amplifier
01171330
FIGURE 16. Low-Power Two-Op-Amp Instrumentation Amplifier
LMC6482
www.national.com19
Typical Single-Supply Applications The circuit in Figure 17 uses a single supply to half wave
rectify a sinusoid centered about ground. R
I
limits current
into the amplifier caused by the input voltage exceeding the
supply voltage. Full wave rectification is provided by the
circuit in Figure 19.
01171331
FIGURE 17. Half-Wave Rectifier
with Input Current Protection (RI)
01171332
FIGURE 18. Half-Wave Rectifier Waveform
01171333
FIGURE 19. Full Wave Rectifier
with Input Current Protection (R
I
)
01171334
FIGURE 20. Full Wave Rectifier Waveform
LMC6482
www.national.com 20
Typical Single-Supply Applications
(Continued)
In Figure 23 dielectric absorption and leakage is minimized
by using a polystyrene or polyethylene hold capacitor. The
droop rate is primarily determined by the value of C
H
and
diode leakage current. The ultra-low input current of the
LMC6482 has a negligible effect on droop.
The LMC6482’s high CMRR (82dB) allows excellent accu-
racy throughout the circuit’s rail-to-rail dynamic capture
range.
01171335
FIGURE 21. Large Compliance Range Current Source
01171336
FIGURE 22. Positive Supply Current Sense
01171337
FIGURE 23. Low Voltage Peak Detector with Rail-to-Rail Peak Capture Range
01171338
FIGURE 24. Rail-to-Rail Sample and Hold
LMC6482
www.national.com21
Typical Single-Supply Applications (Continued)
The low pass filter circuit in Figure 25 can be used as an
anti-aliasing filter with the same voltage supply as the A/D
converter.
Filter designs can also take advantage of the LMC6482
ultra-low input current. The ultra-low input current yields
negligible offset error even when large value resistors are
used. This in turn allows the use of smaller valued capacitors
which take less board space and cost less.
Ordering Information
Package Temperature Range NSC
Drawing
Transport
Media
Package Marking
Military Industrial
−55˚C to +125˚C −40˚C to +85˚C
8-Pin LMC6482AIN, N08E Rail LMC6482MN,
Molded DIP LMC6482IN LMC6482AIN, LMC6482IN
8-pin LMC6482AIM,
LMC6482AIMX M08A Rail LMC6482AIM, LMC6482IM
Small Outline LMC6482IM,
LMC6482IMX
Tape and Reel
8-pin LMC6482AMJ/883 J08A Rail LMC6482AMJ/883Q5962-9453401MPA
Ceramic DIP
8-pin LMC6482IMM MUA08A Rail A10
Mini SO LMC6482IMMX Tape and Reel
01171327
FIGURE 25. Rail-to-Rail Single Supply Low Pass Filter
LMC6482
www.national.com 22
Physical Dimensions inches (millimeters) unless otherwise noted
8-Pin Ceramic Dual-In-Line Package
Order Number LMC6482AMJ/883
NS Package Number J08A
8-Pin Small Outline Package
Order Package Number LMC6482AIM, LMC6482AIMX, LMC6482IM or LMC6482IMX
NS Package Number M08A
LMC6482
www.national.com23
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
8-Pin Molded Dual-In-Line Package
Order Package Number LMC6482AIN, LMC6482IN
NS Package Number N08E
8-Lead Mini Small Outline Molded Package, JEDEC
Order Number LMC6482IMM, or LMC6482IMMX
NS Package Number MUA08A
LMC6482
www.national.com 24
Notes
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves
the right at any time without notice to change said circuitry and specifications.
For the most current product information visit us at www.national.com.
LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS
WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR
CORPORATION. As used herein:
1. Life support devices or systems are devices or systems
which, (a) are intended for surgical implant into the body, or
(b) support or sustain life, and whose failure to perform when
properly used in accordance with instructions for use
provided in the labeling, can be reasonably expected to result
in a significant injury to the user.
2. A critical component is any component of a life support
device or system whose failure to perform can be reasonably
expected to cause the failure of the life support device or
system, or to affect its safety or effectiveness.
BANNED SUBSTANCE COMPLIANCE
National Semiconductor certifies that the products and packing materials meet the provisions of the Customer Products Stewardship
Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification (CSP-9-111S2) and contain no ‘‘Banned
Substances’’ as defined in CSP-9-111S2.
National Semiconductor
Americas Customer
Support Center
Email: new.feedback@nsc.com
Tel: 1-800-272-9959
National Semiconductor
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Fax: +49 (0) 180-530 85 86
Email: europe.support@nsc.com
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Email: ap.support@nsc.com
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Fax: 81-3-5639-7507
Email: jpn.feedback@nsc.com
Tel: 81-3-5639-7560
www.national.com
LMC6482 CMOS Dual Rail-To-Rail Input and Output Operational Amplifier
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