LMC6462,LMC6464
LMC6462 Dual/LMC6464 Quad Micropower, Rail-to-Rail Input and Output CMOS
Operational Amplifier
Literature Number: SNOS725C
LMC6462 Dual/LMC6464 Quad
Micropower, Rail-to-Rail Input and Output CMOS
Operational Amplifier
General Description
The LMC6462/4 is a micropower version of the popular
LMC6482/4, combining Rail-to-Rail Input and Output Range
with very low power consumption.
The LMC6462/4 provides an input common-mode voltage
range that exceeds both rails. The rail-to-rail output swing of
the amplifier, guaranteed for loads down to 25 kΩ, assures
maximum dynamic sigal range. This rail-to-rail performance
of the amplifier, combined with its high voltage gain makes it
unique among rail-to-rail amplifiers. The LMC6462/4 is an
excellent upgrade for circuits using limited common-mode
range amplifiers.
The LMC6462/4, with guaranteed specifications at 3V and
5V, is especially well-suited for low voltage applications. A
quiescent power consumption of 60 µW per amplifier (at V
S
= 3V) can extend the useful life of battery operated systems.
The amplifier’s 150 fA input current, low offset voltage of
0.25 mV, and 85 dB CMRR maintain accuracy in battery-
powered systems.
Features
(Typical unless otherwise noted)
nUltra Low Supply Current 20 µA/Amplifier
nGuaranteed Characteristics at 3V and 5V
nRail-to-Rail Input Common-Mode Voltage Range
nRail-to-Rail Output Swing
(within 10 mV of rail, V
S
= 5V and R
L
=25kΩ)
nLow Input Current 150 fA
nLow Input Offset Voltage 0.25 mV
Applications
nBattery Operated Circuits
nTransducer Interface Circuits
nPortable Communication Devices
nMedical Applications
nBattery Monitoring
8-Pin DIP/SO 14-Pin DIP/SO
01205101
Top View
01205102
Top View
Low-Power Two-Op-Amp Instrumentation Amplifier
01205121
February 2004
LMC6462 Dual/LMC6464 Quad Micropower, Rail-to-Rail Input and Output CMOS Operational
Amplifier
© 2004 National Semiconductor Corporation DS012051 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) 2.0 kV
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) ±30 mA
Current at Power Supply Pin 40 mA
Lead Temp. (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
LMC6462AM, LMC6464AM −55˚C ≤T
J
≤
+125˚C
LMC6462AI, LMC6464AI −40˚C ≤T
J
≤+85˚C
LMC6462BI, LMC6464BI −40˚C ≤T
J
≤+85˚C
Thermal Resistance (θ
JA
)
N Package, 8-Pin Molded DIP 115˚C/W
M Package, 8-Pin Surface
Mount 193˚C/W
N Package, 14-Pin Molded DIP 81˚C/W
M Package, 14-Pin
Surface Mount 126˚C/W
5V 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.
LMC6462AI LMC6462BI LMC6462AM
Symbol Parameter Conditions Typ LMC6464AI LMC6464BI LMC6464AM Units
(Note 5) Limit Limit Limit
(Note 6) (Note 6) (Note 6)
V
OS
Input Offset Voltage 0.25 0.5 3.0 0.5 mV
1.2 3.7 1.5 max
TCV
OS
Input Offset Voltage 1.5 µV/˚C
Average Drift
I
B
Input Current (Note 13) 0.15 10 10 200 pA max
I
OS
Input Offset Current (Note 13) 0.075 5 5 100 pA max
C
IN
Common-Mode 3 pF
Input Capacitance
R
IN
Input Resistance >10 Tera Ω
CMRR Common Mode 0V ≤V
CM
≤15.0V, 85 70 65 70 dB
min
Rejection Ratio V
+
= 15V 67 62 65
0V ≤V
CM
≤5.0V 85 70 65 70
V
+
=5V 67 62 65
+PSRR Positive Power Supply 5V ≤V
+
≤15V, 85 70 65 70 dB
Rejection Ratio V
−
= 0V, V
O
= 2.5V 67 62 65 min
−PSRR Negative Power Supply −5V ≤V
−
≤−15V, 85 70 65 70 dB
Rejection Ratio V
+
= 0V, V
O
= −2.5V 67 62 65 min
V
CM
Input Common-Mode V
+
= 5V −0.2 −0.10 −0.10 −0.10 V
Voltage Range For CMRR ≥50 dB 0.00 0.00 0.00 max
5.30 5.25 5.25 5.25 V
5.00 5.00 5.00 min
V
+
= 15V −0.2 −0.15 −0.15 −0.15 V
For CMRR ≥50 dB 0.00 0.00 0.00 max
15.30 15.25 15.25 15.25 V
15.00 15.00 15.00 min
LMC6462 Dual/LMC6464 Quad
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5V 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.
LMC6462AI LMC6462BI LMC6462AM
Symbol Parameter Conditions Typ LMC6464AI LMC6464BI LMC6464AM Units
(Note 5) Limit Limit Limit
(Note 6) (Note 6) (Note 6)
A
V
Large Signal R
L
= 100 kΩSourcing 3000 V/mV
Voltage Gain (Note 7) min
Sinking 400 V/mV
min
R
L
=25kΩSourcing 2500 V/mV
(Note 7) min
Sinking 200 V/mV
min
V
O
Output Swing V
+
= 5V 4.995 4.990 4.950 4.990 V
R
L
= 100 kΩto V
+
/2 4.980 4.925 4.970 min
0.005 0.010 0.050 0.010 V
0.020 0.075 0.030 max
V
+
= 5V 4.990 4.975 4.950 4.975 V
R
L
=25kΩto V
+
/2 4.965 4.850 4.955 min
0.010 0.020 0.050 0.020 V
0.035 0.150 0.045 max
V
+
= 15V 14.990 14.975 14.950 14.975 V
R
L
= 100 kΩto V
+
/2 14.965 14.925 14.955 min
0.010 0.025 0.050 0.025 V
0.035 0.075 0.050 max
V
+
= 15V 14.965 14.900 14.850 14.900 V
R
L
=25kΩto V
+
/2 14.850 14.800 14.800 min
0.025 0.050 0.100 0.050 V
0.150 0.200 0.200 max
I
SC
Output Short Circuit Sourcing, V
O
=0V 27 19 19 19 mA
Current 15 15 15 min
V+ = 5V Sinking, V
O
=5V 27 22 22 22 mA
17 17 17 min
I
SC
Output Short Circuit Sourcing, V
O
=0V 38 24 24 24 mA
Current 17 17 17 min
V
+
= 15V Sinking, V
O
= 12V 75 55 55 55 mA
(Note 8) 45 45 45 min
I
S
Supply Current Dual, LMC6462 40 55 55 55 µA
V
+
= +5V, V
O
=V
+
/2 70 70 75 max
Quad, LMC6464 80 110 110 110 µA
V
+
= +5V, V
O
=V
+
/2 140 140 150 max
Dual, LMC6462 50 60 60 60 µA
V
+
= +15V, V
O
=V
+
/2 70 70 75 max
Quad, LMC6464 90 120 120 120 µA
V
+
= +15V, V
O
=V
+
/2 140 140 150 max
LMC6462 Dual/LMC6464 Quad
www.national.com3
5V 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.
LMC6462AI LMC6462BI LMC6462AM
Symbol Parameter Conditions Typ LMC6464AI LMC6464BI LMC6464AM Units
(Note 5) Limit Limit Limit
(Note 6) (Note 6) (Note 6)
SR Slew Rate (Note 9) 28 15 15 15 V/ms
888min
GBW Gain-Bandwidth Product V
+
= 15V 50 kHz
φ
m
Phase Margin 50 Deg
G
m
Gain Margin 15 dB
Amp-to-Amp Isolation (Note 10) 130 dB
e
n
Input-Referred f = 1 kHz 80
Voltage Noise V
CM
=1V
i
n
Input-Referred f = 1 kHz 0.03
Current Noise
3V 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. Boldface
limits apply at the temperature extremes.
LMC6462AI LMC6462BI LMC6462AM
Symbol Parameter Conditions Typ LMC6464AI LMC6464BI LMC6464AM Units
(Note 5) Limit Limit Limit
(Note 6) (Note 6) (Note 6)
V
OS
Input Offset Voltage 0.9 2.0 3.0 2.0 mV
2.7 3.7 3.0 max
TCV
OS
Input Offset Voltage 2.0 µV/˚C
Average Drift
I
B
Input Current (Note 13) 0.15 10 10 200 pA
I
OS
Input Offset Current (Note 13) 0.075 5 5 100 pA
CMRR Common Mode 0V ≤V
CM
≤3V 74 60 60 60 dB
Rejection Ratio min
PSRR Power Supply 3V ≤V
+
≤15V, V
−
=0V 80 60 60 60 dB
Rejection Ratio min
V
CM
Input Common-Mode For CMRR ≥50 dB −0.10 0.0 0.0 0.0 V
Voltage Range max
3.0 3.0 3.0 3.0 V
min
V
O
Output Swing R
L
=25kΩto V
+
/2 2.95 2.9 2.9 2.9 V
min
0.15 0.1 0.1 0.1 V
max
I
S
Supply Current Dual, LMC6462 40 55 55 55 µA
V
O
=V
+
/2 70 70 70
Quad, LMC6464 80 110 110 110 µA
V
O
=V
+
/2 140 140 140 max
LMC6462 Dual/LMC6464 Quad
www.national.com 4
3V AC Electrical Characteristics
Unless otherwise specified, V
+
= 3V, V
−
= 0V, V
CM
=V
O
=V
+
/2 and R
L
>1M. Boldface limits apply at the temperature ex-
tremes.
LMC6462AI LMC6462BI LMC6462AM
Symbol Parameter Conditions Typ LMC6464AI LMC6464BI LMC6464AM Units
(Note 5) Limit Limit Limit
(Note 6) (Note 6) (Note 6)
SR Slew Rate (Note 11) 23 V/ms
GBW Gain-Bandwidth Product 50 kHz
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 the test conditions, see the Electrical Characteristics.
Note 2: Human body model, 1.5 kΩin series with 100 pF. All pins rated per method 3015.6 of MIL-STD-883. This is a class 2 device rating.
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 ±30 mA 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 Range parameters see RETSMC6462/4X.
LMC6462 Dual/LMC6464 Quad
www.national.com5
Typical Performance Characteristics V
S
= +5V, Single Supply, T
A
= 25˚C unless otherwise speci-
fied
Supply Current vs. Supply Voltage Sourcing Current vs. Output Voltage
01205130 01205131
Sourcing Current vs. Output Voltage Sourcing Current vs. Output Voltage
01205132 01205133
Sinking Current vs. Output Voltage Sinking Current vs. Output Voltage
01205134 01205135
LMC6462 Dual/LMC6464 Quad
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Typical Performance Characteristics V
S
= +5V, Single Supply, T
A
= 25˚C unless otherwise
specified (Continued)
Sinking Current vs. Output Voltage Input Voltage Noise vs Frequency
01205136 01205137
Input Voltage Noise vs. Input Voltage Input Voltage Noise vs. Input Voltage
01205138 01205139
Input Voltage Noise vs. Input Voltage ∆V
OS
vs CMR
01205140 01205141
LMC6462 Dual/LMC6464 Quad
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Typical Performance Characteristics V
S
= +5V, Single Supply, T
A
= 25˚C unless otherwise
specified (Continued)
Input Voltage vs. Output Voltage Open Loop Frequency Response
01205142
01205143
Open Loop Frequency Response vs. Temperature Gain and Phase vs. Capacitive Load
01205144 01205145
Slew Rate vs. Supply Voltage Non-Inverting Large Signal Pulse Response
01205146 01205147
LMC6462 Dual/LMC6464 Quad
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Typical Performance Characteristics V
S
= +5V, Single Supply, T
A
= 25˚C unless otherwise
specified (Continued)
Non-Inverting Large Signal Pulse Response Non-Inverting Large Signal Pulse Response
01205148 01205149
Non-Inverting Small Signal Pulse Response Non-Inverting Small Signal Pulse Response
01205150 01205151
Non-Inverting Small Signal Pulse Response Inverting Large Signal Pulse Response
01205152 01205153
LMC6462 Dual/LMC6464 Quad
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Typical Performance Characteristics V
S
= +5V, Single Supply, T
A
= 25˚C unless otherwise
specified (Continued)
Inverting Large Signal Pulse Response Inverting Large Signal Pulse Response
01205154 01205155
Inverting Small Signal Pulse Response Inverting Small Signal Pulse Response
01205156 01205157
Inverting Small Signal Pulse Response
01205158
LMC6462 Dual/LMC6464 Quad
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Application Information
1.0 INPUT COMMON-MODE VOLTAGE RANGE
The LMC6462/4 has a rail-to-rail input common-mode volt-
age range. Figure 1 shows an input voltage exceeding both
supplies with no resulting phase inversion on the output.
The absolute maximum input voltage at V
+
= 3V is 300 mV
beyond either supply rail at room temperature. Voltages
greatly exceeding this absolute maximum rating, as in Figure
2, can cause excessive current to flow in or out of the input
pins, possibly affecting reliability. The input current can be
externally limited to ±5 mA, with an input resistor, as shown
in Figure 3.
2.0 RAIL-TO-RAIL OUTPUT
The approximated output resistance of the LMC6462/4 is
180Ωsourcing, and 130Ωsinking at V
S
= 3V, and 110Ω
sourcing and 83Ωsinking at V
S
= 5V. The maximum output
swing can be estimated as a function of load using the
calculated output resistance.
3.0 CAPACITIVE LOAD TOLERANCE
The LMC6462/4 can typically drive a 200 pF load with V
S
=
5V at unity gain without oscillating. The unity gain follower is
the most sensitive configuration to capacitive load. Direct
capacitive loading reduces the phase margin of op-amps.
The combination of the op-amp’s output impedance and the
capacitive load induces phase lag. This results in either an
underdamped pulse response or oscillation.
Capacitive load compensation can be accomplished using
resistive isolation as shown in Figure 4. If there is a resistive
component of the load in parallel to the capacitive compo-
nent, the isolation resistor and the resistive load create a
voltage divider at the output. This introduces a DC error at
the output.
Figure 5 displays the pulse response of the LMC6462/4
circuit in Figure 4.
Another circuit, shown in Figure 6, is also used to indirectly
drive capacitive loads. This circuit is an improvement to the
circuit shown in Figure 4 because it provides DC accuracy as
well as AC stability. R1 and C1 serve to counteract the loss
of phase margin by feeding the high frequency component of
the output signal back to the amplifiers inverting input,
thereby preserving phase margin in the overall feedback
loop. The values of R1 and C1 should be experimentally
determined by the system designer for the desired pulse
response. Increased capacitive drive is possible by increas-
ing the value of the capacitor in the feedback loop.
01205105
FIGURE 1. An Input Voltage Signal Exceeds
the LMC6462/4 Power Supply Voltage
with No Output Phase Inversion
01205106
FIGURE 2. A ±7.5V Input Signal Greatly Exceeds
the 3V Supply in Figure 3 Causing
No Phase Inversion Due to R
I
01205107
FIGURE 3. Input Current Protection for Voltages
Exceeding the Supply Voltage
01205108
FIGURE 4. Resistive Isolation of
a 300 pF Capacitive Load
01205109
FIGURE 5. Pulse Response of the LMC6462
Circuit Shown in Figure 4
LMC6462 Dual/LMC6464 Quad
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Application Information (Continued)
The pulse response of the circuit shown in Figure 6 is shown
in Figure 7.
4.0 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 LMC6462/4. Large feedback resistors can react with
small values of input capacitance due to transducers, pho-
todiodes, 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 breadboard, 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.)
5.0 OFFSET VOLTAGE ADJUSTMENT
Offset voltage adjustment circuits are illustrated in Figure 9
and Figure 10. Large value resistances and potentiometers
are used to reduce power consumption while providing typi-
cally ±2.5 mV of adjustment range, referred to the input, for
both configurations with V
S
=±5V.
6.0 SPICE MACROMODEL
A Spice macromodel is available for the LMC6462/4. This
model includes a 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
01205110
FIGURE 6. LMC6462 Non-Inverting Amplifier,
Compensated to Handle a 300 pF Capacitive
and 100 kΩResistive Load
01205111
FIGURE 7. Pulse Response of
LMC6462 Circuit in Figure 6
01205112
FIGURE 8. Canceling the Effect of Input Capacitance
01205113
FIGURE 9. Inverting Configuration
Offset Voltage Adjustment
01205114
FIGURE 10. Non-Inverting Configuration
Offset Voltage Adjustment
LMC6462 Dual/LMC6464 Quad
www.national.com 12
Application Information (Continued)
and many more characteristics as listed on the macromodel
disk.
Contact the National Semiconductor Customer Response
Center to obtain an operational amplifier Spice model library
disk.
7.0 PRINTED-CIRCUIT-BOARD LAYOUT FOR
HIGH-IMPEDANCE WORK
It is generally recognized that any circuit which must operate
with less than 1000 pA of leakage current requires special
layout of the PC board. When one wishes to take advantage
of the ultra-low input current of the LMC6462/4, typically 150
fA, 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 though 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 LMC6462’s inputs and the
terminals of capacitors, diodes, conductors, resistors, relay
terminals, etc. connected to the op-amp’s inputs, as in Fig-
ure 11. To have a significant effect, guard rings should be
placed in 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 5 pA if
the trace were a 5V bus adjacent to the pad of the input. This
would cause a 30 times degradation from the LMC6462/4’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 0.05 pA of leakage current. See Figure 12 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
13.
01205115
FIGURE 11. Example of Guard Ring in P.C. Board
Layout
01205116
Inverting Amplifier
01205117
Non-Inverting Amplifier
01205118
Follower
FIGURE 12. Typical Connections of Guard Rings
LMC6462 Dual/LMC6464 Quad
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Application Information (Continued) 8.0 INSTRUMENTATION CIRCUITS
The LMC6464 has the high input impedance, large common-
mode range and high CMRR needed for designing instru-
mentation circuits. Instrumentation circuits designed with the
LMC6464 can reject a larger range of common-mode signals
than most in-amps. This makes instrumentation circuits de-
signed with the LMC6464 an excellent choice for noisy or
industrial environments. Other applications that benefit from
these features include analytic medical instruments, mag-
netic field detectors, gas detectors, and silicon-based trans-
ducers.
A small valued potentiometer is used in series with R
G
to set
the differential gain of the three op-amp instrumentation
circuit in Figure 14. This combination is used instead of one
large valued potentiometer to increase gain trim accuracy
and reduce error due to vibration.
A two op-amp instrumentation amplifier designed for a gain
of 100 is shown in Figure 15. 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.
01205119
(Input pins are lifted out of PC board and soldered directly to components.
All other pins connected to PC board.)
FIGURE 13. Air Wiring
01205120
FIGURE 14. Low Power Three Op-Amp Instrumentation Amplifier
LMC6462 Dual/LMC6464 Quad
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Application Information (Continued)
Typical Single-Supply Applications
TRANSDUCER INTERFACE CIRCUITS
Photocells can be used in portable light measuring instru-
ments. The LMC6462, which can be operated off a battery, is
an excellent choice for this circuit because of its very low
input current and offset voltage.
LMC6462 AS A COMPARATOR
Figure 17 shows the application of the LMC6462 as a com-
parator. The hysteresis is determined by the ratio of the two
resistors. The LMC6462 can thus be used as a micropower
comparator, in applications where the quiescent current is an
important parameter.
HALF-WAVE AND FULL-WAVE RECTIFIERS
In Figure 18 Figure 19,R
I
limits current into the amplifier
since excess current can be caused by the input voltage
exceeding the supply voltage.
01205121
FIGURE 15. Low-Power Two-Op-Amp Instrumentation Amplifier
01205122
FIGURE 16. Photo Detector Circuit
01205123
FIGURE 17. Comparator with Hysteresis
01205124
FIGURE 18. Half-Wave Rectifier with
Input Current Protection (R
I
)
01205125
FIGURE 19. Full-Wave Rectifier
with Input Current Protection (R
I
)
LMC6462 Dual/LMC6464 Quad
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Typical Single-Supply Applications
(Continued)
PRECISION CURRENT SOURCE
The output current I
OUT
is given by:
OSCILLATORS
For single supply 5V operation, the output of the circuit will
swing from 0V to 5V. The voltage divider set up R
2
,R
3
and
R
4
will cause the non-inverting input of the LMC6462 to
move from 1.67V (
1
⁄
3
of 5V) to 3.33V (
2
⁄
3
of 5V). This voltage
behaves as the threshold voltage.
R
1
and C
1
determine the time constant of the circuit. The
frequency of oscillation, f
OSC
is
where ∆t is the time the amplifier input takes to move from
1.67V to 3.33V. The calculations are shown below.
where τ= RC = 0.68 seconds
→t
1
= 0.27 seconds.
and
→t
2
= 0.75 seconds
Then,
=1Hz
LOW FREQUENCY NULL
Output offset voltage is the error introduced in the output
voltage due to the inherent input offset voltage V
OS
,ofan
amplifier.
Output Offset Voltage = (Input Offset Voltage) (Gain)
In the above configuration, the resistors R
5
and R
6
deter-
mine the nominal voltage around which the input signal, V
IN
should be symmetrical. The high frequency component of
the input signal V
IN
will be unaffected while the low fre-
quency component will be nulled since the DC level of the
output will be the input offset voltage of the LMC6462 plus
the bias voltage. This implies that the output offset voltage
due to the top amplifier will be eliminated.
01205126
FIGURE 20. Precision Current Source
01205127
FIGURE 21. 1 Hz Square-Wave Oscillator
01205128
FIGURE 22. High Gain Amplifier
with Low Frequency Null
LMC6462 Dual/LMC6464 Quad
www.national.com 16
Ordering Information
Package Temperature Range Transport NSC
Military Industrial Media Drawing
−55˚C to +125˚C −40˚C to +85˚C
8-Pin Molded DIP LMC6462AIN 40 Units/Rail N08E
LMC6462BIN
8-Pin SO-8
LMC6462AIM 95 Units/Rail
M08A
LMC6462BIM
LMC6462AIMX 2.5k Tape and Reel
LMC6462BIMX
14-Pin Molded DIP LMC6464AIN 25 Units/Rail N14A
LMC6464BIN
14-Pin SO-14
LMC6464AIM 55 Units/Rail
M14A
LMC6464BIM
LMC6464AIMX 2.5k Tape and Reel
LMC6464BIMX
8-Pin Ceramic DIP LMC6462AMJ-QML Rails J08A
14-Pin Ceramic DIP LMC6464AMJ-QML Rails J14A
14-Pin Ceramic SOIC LMC6464AMWG-QML Trays WG14A
LMC6462 Dual/LMC6464 Quad
www.national.com17
Physical Dimensions inches (millimeters)
unless otherwise noted
8-Pin Small Outline Package
NS Package Number M08A
14-Pin Small Outline Package
NS Package Number M14A
LMC6462 Dual/LMC6464 Quad
www.national.com 18
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
8-Pin Molded Dual-In-Line Package
NS Package Number N08E
14-Pin Molded Dual-In-Line Pacakge
NS Package Number N14A
LMC6462 Dual/LMC6464 Quad
www.national.com19
Notes
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
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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
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National Semiconductor
Americas Customer
Support Center
Email: new.feedback@nsc.com
Tel: 1-800-272-9959
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www.national.com
LMC6462 Dual/LMC6464 Quad Micropower, Rail-to-Rail Input and Output CMOS Operational
Amplifier
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.
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