National Semiconductor is now part of
Texas Instruments.
Search http://www.ti.com/ for the latest technical
information and details on our current products and services.
LMC6042
CMOS Dual Micropower Operational Amplifier
General Description
Features
Ultra-low power consumption and low input-leakage current
are the hallmarks of the LMC6042. Providing input currents
of only 2 fA typical, the LMC6042 can operate from a single
supply, has output swing extending to each supply rail, and
an input voltage range that includes ground.
The LMC6042 is ideal for use in systems requiring ultra-low
power consumption. In addition, the insensitivity to latch-up,
high output drive, and output swing to ground without requiring external pull-down resistors make it ideal for singlesupply battery-powered systems.
n
n
n
n
n
Other applications for the LMC6042 include bar code reader
amplifiers, magnetic and electric field detectors, and handheld electrometers.
This device is built with National’s advanced Double-Poly
Silicon-Gate CMOS process.
Low supply current: 10 µA/Amp (typ)
Operates from 4.5V to 15V single supply
Ultra low input current: 2 fA (typ)
Rail-to-rail output swing
Input common-mode range includes ground
Applications
n
n
n
n
n
n
n
Battery monitoring and power conditioning
Photodiode and infrared detector preamplifier
Silicon based transducer systems
Hand-held analytic instruments
pH probe buffer amplifier
Fire and smoke detection systems
Charge amplifier for piezoelectric transducers
See the LMC6041 for a single, and the LMC6044 for a quad
amplifier with these features.
Connection Diagram
8-Pin DIP/SO
01113701
Low-Power Two-Op-Amp Instrumental Amplifier
01113713
© 2004 National Semiconductor Corporation
DS011137
www.national.com
LMC6042 CMOS Dual Micropower Operational Amplifier
August 2000
LMC6042
Absolute Maximum Ratings (Note 1)
Junction Temperature (Note 3)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
ESD Tolerance (Note 4)
Differential Input Voltage
500V
(V+) + 0.3V, (V−) −
0.3V
Voltage at Input/Output Pin
± Supply Voltage
Supply Voltage (V+ − V−)
16V
Output Short Circuit to V+
(Note 12)
Output Short Circuit to V−
(Note 2)
Operating Ratings
Temperature Range
−40˚C ≤ TJ ≤
+85˚C
LMC6042AI, LMC6042I
Lead Temperature
(Soldering, 10 seconds)
260˚C
Current at Output Pin
Current at Power Supply Pin
Power Dissipation
(Note 10)
Thermal Resistance (θJA), (Note 11)
35 mA
Power Dissipation
4.5V ≤ V+ ≤ 15.5V
Supply Voltage
± 5 mA
± 18 mA
Current at Input Pin
Storage Temperature Range
110˚C
(Note 3)
−65˚C to +150˚C
8-Pin DIP
101˚C/W
8-Pin SO
165˚C/W
Electrical Characteristics
Unless otherwise spec ified, all limits guaranteed for TA = TJ = 25˚C. Boldface limits apply at the temperature extremes. V+ =
5V, V− = 0V, VCM = 1.5V, VO = V+/2 and RL > 1M unless otherwise specified.
Symbol
VOS
TCVOS
Parameter
Conditions
Input Offset Voltage
Typical
LMC6042AI
LMC6042I
Units
(Note 5)
Limit
Limit
(Limit)
(Note 6)
(Note 6)
1
Input Offset Voltage
3
6
mV
3.3
6.3
Max
1.3
µV/˚C
Average Drift
IB
Input Bias Current
0.002
4
4
pA (Max)
IOS
Input Offset Current
0.001
2
2
pA (Max)
RIN
Input Resistance
CMRR
Common Mode
0V ≤ VCM ≤ 12.0V
Rejection Ratio
V+ = 15V
Positive Power Supply
5V ≤ V+ ≤ 15V
Rejection Ratio
VO = 2.5V
Negative Power Supply
0V ≤ V− ≤ −10V
Rejection Ratio
VO = 2.5V
Input Common-Mode
V+ = 5V and 15V
Voltage Range
For CMRR ≥ 50 dB
+PSRR
−PSRR
CMR
AV
Large Signal
> 10
RL = 100 kΩ (Note 7)
75
68
62
dB
66
60
Min
68
62
dB
66
60
Min
84
74
dB
83
73
Min
−0.4
−0.1
−0.1
V
0
0
Max
V+−1.9V
V+− 2.3V
V+− 2.3V
V
V+− 2.5V
V+− 2.4V
Min
400
300
V/mV
300
200
Min
180
90
V/mV
120
70
Min
200
100
V/mV
160
80
Min
100
50
V/mV
60
40
Min
75
94
Sourcing
1000
Voltage Gain
Sinking
RL = 25 kΩ (Note 7)
Sourcing
Sinking
www.national.com
2
TeraΩ
500
1000
250
(Continued)
Unless otherwise spec ified, all limits guaranteed for TA = TJ = 25˚C. Boldface limits apply at the temperature extremes. V+ =
5V, V− = 0V, VCM = 1.5V, VO = V+/2 and RL > 1M unless otherwise specified.
Symbol
VO
Parameter
Output Swing
Conditions
V+ = 5V
Typical
LMC6042AI
LMC6042I
Units
(Note 5)
Limit
Limit
(Limit)
(Note 6)
(Note 6)
4.970
4.940
V
4.950
4.910
Min
0.030
0.060
V
0.050
0.090
Max
4.987
RL = 100 kΩ to V+/2
0.004
V+ = 5V
4.980
RL = 25 kΩ to V+/2
0.010
V+ = 15V
14.970
+
RL = 100 kΩ to V /2
0.007
V+ = 15V
14.950
RL = 25 kΩ to V+/2
0.022
ISC
Output Current
Sourcing, VO = 0V
22
V+ = 5V
ISC
Output Current
V
Min
0.080
0.130
V
0.130
0.180
Max
14.920
14.880
V
14.880
14.820
Min
0.030
0.060
V
0.050
0.090
Max
14.900
14.850
V
14.850
14.800
Min
0.100
0.150
V
0.150
0.200
Max
16
13
mA
10
8
Min
13
mA
Min
21
16
8
8
Sourcing, VO = 0V
40
15
15
mA
10
10
Min
39
24
21
mA
8
8
Min
20
34
45
µA
39
50
Max
44
56
µA
51
65
Max
Sinking, VO = 13V
(Note 12)
Supply Current
4.870
4.820
Sinking, VO = 5V
V+ = 15V
IS
4.920
4.870
Both Amplifiers
VO = 1.5V
Both Amplifiers
26
V+ = 15V
AC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TA = TJ = 25˚C. Boldface limits apply at the temperature extremes. V+ =
5V, V− = 0V, VCM = 1.5V, VO = V+/2 and RL > 1M unless otherwise specified.
Symbol
Parameter
Conditions
LMC6042AI
LMC6042I
Units
Limit
Limit
(Limit)
(Note 6)
(Note 6)
0.015
0.010
0.010
0.007
SR
Slew Rate
GBW
Gain-Bandwidth Product
100
kHz
φm
Phase Margin
60
Deg
dB
en
in
(Note 8)
Typ
(Note 5)
0.02
Amp-to-Amp Isolation
(Note 9)
115
Input-Referred
Voltage Noise
f = 1 kHz
83
Input-Referred
Current Noise
f = 1 kHz
V/µs
Min
0.0002
3
www.national.com
LMC6042
Electrical Characteristics
LMC6042
AC Electrical Characteristics
(Continued)
Unless otherwise specified, all limits guaranteed for TA = TJ = 25˚C. Boldface limits apply at the temperature extremes. V+ =
5V, V− = 0V, VCM = 1.5V, VO = V+/2 and RL > 1M unless otherwise specified.
Symbol
T.H.D.
Parameter
Total Harmonic Distortion
Conditions
Typ
LMC6042AI
LMC6042I
Units
(Note 5)
Limit
Limit
(Limit)
(Note 6)
(Note 6)
f = 1 kHz, AV = −5
RL = 100 kΩ, VO = 2 VPP
0.01
%
± 5V Supply
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Conditions indicate conditions for which the device
is intended to be functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics.
The guaranteed specifications apply only for the test conditions listed.
Note 2: Applies to both single-supply operation. Continuous short circuit operation at elevated ambient temperature can result in exceeding the maximum allowed
junction temperature of 110˚C. Output currents in excess of ± 30 mA over long term may adversely affect reliability.
Note 3: The maximum power dissipation is a function of TJ(Max), θJA, and TA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(Max)
− TA)/θJA.
Note 4: Human body model, 1.5 kΩ in series with 100 pF.
Note 5: Typical values represent the most likely parametric norm.
Note 6: All limits are guaranteed at room temperature (standard type face) or at operating temperature extremes (bold face type).
Note 7: V+ = 15V, VCM = 7.5V and RL connected to 7.5V. For Sourcing tests, 7.5V ≤ VO ≤ 11.5V. For Sinking tests, 2.5V ≤ VO ≤ 7.5V.
Note 8: V+ = 15V. Connected as Voltage Follower with 10V step input. Number specified is the slower of the positive and negative slew rates.
Note 9: Input referred V+ = 15V and RL = 100 kΩ connected to V+/2. Each amp excited in turn with 100 Hz to produce VO = 12 VPP.
Note 10: For operating at elevated temperatures the device must be derated based on the thermal resistance θJA with PD = (TJ − TA)/θJA.
Note 11: All numbers apply for packages soldered directly into a PC board.
Note 12: Do not connect output to V+when V+ is greater than 13V or reliability may be adversely affected.
Typical Performance Characteristics
VS = ± 7.5V, TA = 25˚C unless otherwise specified
Offset Voltage vs
Temperature of Five
Representative Units
Supply Current vs
Supply Voltage
01113719
www.national.com
01113720
4
(Continued)
Input Bias Current
vs Input Common-Mode
Voltage
Input Bias Current
vs Temperature
01113721
01113722
Input Bias Current
Voltage Range
vs Temperature
Output Characteristics
Current Sinking
01113723
01113724
Output Characteristics
Current Sourcing
Input Voltage Noise
vs Frequency
01113725
01113726
5
www.national.com
LMC6042
Typical Performance Characteristics VS = ±7.5V, TA = 25˚C unless otherwise specified
LMC6042
Typical Performance Characteristics VS = ±7.5V, TA = 25˚C unless otherwise specified
Crosstalk Rejection
vs Frequency
CMRR vs Frequency
01113728
01113727
Power Supply Rejection
Ratio vs Frequency
CMRR vs Temperature
01113729
01113730
Open-Loop Voltage
Gain vs Temperature
Open-Loop
Frequency Response
01113732
01113731
www.national.com
(Continued)
6
Gain and Phase
Responses vs
Load Capacitance
(Continued)
Gain and Phase
Response vs
Temperature
01113733
01113734
Common-Mode Error vs
Common-Mode Voltage of
3 Representative Units
Gain Error
(VOS vs VOUT)
01113736
01113735
Non-Inverting Slew
Rate vs Temperature
Inverting Slew Rate
vs Temperature
01113737
01113738
7
www.national.com
LMC6042
Typical Performance Characteristics VS = ±7.5V, TA = 25˚C unless otherwise specified
LMC6042
Typical Performance Characteristics VS = ±7.5V, TA = 25˚C unless otherwise specified
Non-Inverting Large
Signal Pulse Response
(AV = +1)
Non-Inverting Small
Signal Pulse Response
01113739
01113740
Inverting Large-Signal
Pulse Response
Inverting Small Signal
Pulse Response
01113741
01113742
Stability vs Capacitive Load
Stability vs Capacitive Load
01113743
www.national.com
(Continued)
01113744
8
AMPLIFIER TOPOLOGY
The LMC6042 incorporates a novel op-amp design topology
that enables it to maintain rail-to-rail output swing even when
driving a large load. Instead of relying on a push-pull unity
gain output buffer stage, the output stage is taken directly
from the internal integrator, which provides both low output
impedance and large gain. Special feed-forward compensation design techniques are incorporated to maintain stability
over a wider range of operating conditions than traditional
micropower op-amps. These features make the LMC6042
both easier to design with, and provide higher speed than
products typically found in this ultra-low power class.
COMPENSATING FOR INPUT CAPACITANCE
It is quite common to use large values of feedback resistance with amplifiers with ultra-low input curent, like the
LMC6042.
Although the LMC6042 is highly stable over a wide range of
operating conditions, certain precautions must be met to
achieve the desired pulse response when a large feedback
resistor is used. Large feedback resistors and even small
values of input capacitance, due to transducers, photodiodes, and circuit board parasitics, reduce phase margins.
When high input impedances are demanded, guarding of the
LMC6042 is suggested. Guarding input lines will not only
reduce leakage, but lowers stray input capacitance as well.
(See Printed-Circuit-Board Layout for High Impedance
Work).
01113706
FIGURE 2. LMC6042 Noninverting Gain of 10 Amplifier,
Compensated to Handle Capacitive Loads
In the circuit of Figure 2, R1 and C1 serve to counteract the
loss of phase margin by feeding the high frequency component of the output signal back to the amplifier’s inverting
input, thereby preserving phase margin in the overall feedback loop.
Capacitive load driving capability is enhanced by using a
pull up resistor to V+ (Figure 3). Typically a pull up resistor
conducting 10 µA or more will significantly improve capacitive load responses. The value of the pull up resistor must be
determined based on the current sinking capability of the
amplifier with respect to the desired output swing. Open loop
gain of the amplifier can also be affected by the pull up
resistor (see Electrical Characteristics).
01113705
FIGURE 1. Cancelling the Effect of Input Capacitance
The effect of input capacitance can be compensated for by
adding a capacitor. Place a capacitor, Cf, around the feedback resistor (as in Figure 1 ) such that:
01113718
FIGURE 3. Compensating for Large
Capacitive Loads with a Pull Up Resistor
or
R1 CIN ≤ R2 Cf
Since it is often difficult to know the exact value of CIN, Cf can
be experimentally adjusted so that the desired pulse response is achieved. Refer to the LMC660 and the LMC662
for a more detailed discussion on compensating for input
capacitance.
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 bias current of the LMC6042, typically less
than 2 fA, it is essential to have an excellent layout. Fortunately, the techniques of obtaining low leakages are quite
9
www.national.com
LMC6042
CAPACITIVE LOAD TOLERANCE
Direct capacitive loading will reduce the phase margin of
many op-amps. A pole in the feedback loop is created by the
combination of the op-amp’s output impedance and the capacitive load. This pole induces phase lag at the unity-gain
crossover frequency of the amplifier resulting in either an
oscillatory or underdamped pulse response. With a few external components, op amps can easily indirectly drive capacitive loads, as shown in Figure 2.
Applications Hints
LMC6042
Applications Hints
(Continued)
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 LMC6042’s inputs and the
terminals of capacitors, diodes, conductors, resistors, relay
terminals etc. connected to the op-amp’s inputs, as in Figure
4. 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 1012Ω, which is normally 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 100 times degradation from the LMC6042’s
actual performance. However, if a guard ring is held within 5
mV of the inputs, then even a resistance of 1011Ω would
cause only 0.05 pA of leakage current. See Figure 5 for
typical connections of guard rings for standard op-amp configurations.
01113708
Inverting Amplifier
01113710
Non-Inverting Amplifier
01113709
Follower
FIGURE 5. Typical Connections of Guard Rings
01113707
FIGURE 4. Example of Guard Ring
in P.C. Board Layout
www.national.com
10
the differential gain will be in the range of 10 to 1000. This
two op-amp instrumentation amplifier features an independent adjustment of the gain and common-mode rejection
trim, and a total quiescent supply current of less than 20 µA.
To maintain ultra-high input impedance, it is advisable to use
ground rings and consider PC board layout an important part
of the overall system design (see Printed-Circuit-Board Layout for High Impedance Work). Referring to Figure 7, the
input voltages are represented as a common-mode input
VCM plus a differential input VD.
(Continued)
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 construction, but the advantages are sometimes well worth the
effort of using point-to-point up-in-the-air wiring. See Figure
6.
Rejection of the common-mode component of the input is
accomplished by making the ratio of R1/R2 equal to R3/R4.
So that where,
A suggested design guideline is to minimize the difference of
value between R1 through R4. This will often result in improved resistor tempco, amplifier gain, and CMRR over temperature. If RN = R1 = R2 = R3 = R4 then the gain equation
can be simplified:
01113711
(Input pins are lifted out of PC board and soldered directly to components.
All other pins connected to PC board.)
FIGURE 6. Air Wiring
Due to the “zero-in, zero-out” performance of the LMC6042,
and output swing rail-rail, the dynamic range is only limited to
the input common-mode range of 0V to VS − 2.3V, worst
case at room temperature. This feature of the LMC6042
makes it an ideal choice for low-power instrumentation systems.
A complete instrumentation amplifier designed for a gain of
100 is shown in Figure 8. Provisions have been made for low
sensitivity trimming of CMRR and gain.
Typical Single-Supply Applications
(V+ = 5.0 VDC)
The extremely high input impedance, and low power consumption, of the LMC6042 make it ideal for applications that
require battery-powered instrumentation amplifiers. Examples of these types of applications are hand-held pH
probes, analytic medical instruments, magnetic field detectors, gas detectors, and silicon based pressure transducers.
The circuit in Figure 7 is recommended for applications
where the common-mode input range is relatively low and
01113712
FIGURE 7. Two Op-Amp Instrumentation Amplifier
11
www.national.com
LMC6042
Applications Hints
LMC6042
Typical Single-Supply Applications (V+ = 5.0 VDC)
(Continued)
01113713
FIGURE 8. Low-Power Two-Op-Amp
Instrumentation Amplifier
01113714
FIGURE 9. Low-Leakage Sample and Hold
01113715
FIGURE 10. Instrumentation Amplifier
www.national.com
12
LMC6042
Typical Single-Supply Applications (V+ = 5.0 VDC)
(Continued)
01113716
FIGURE 11. 1 Hz Square Wave Oscillator
01113717
FIGURE 12. AC Coupled Power Amplifier
Ordering Information
Temperature
Package
Range
NSC
Industrial
Drawing
Transport
Media
−40˚C to +85˚C
8-Pin
LMC6042AIM, LMC6042AIMX
Small Outline
LMC6042IM, LMC6042IMX
8-Pin
LMC6042AIN
Molded DIP
LMC6042IN
M08A
N08E
13
Rail
Tape and Reel
Rail
www.national.com
LMC6042
Physical Dimensions
inches (millimeters)
unless otherwise noted
8-Pin Small Outline Package
Order Number LMC6042AIM, LMC6042AIMX, LMC6042IM or LMC6042IMX
NS Package Number M08A
8-Pin Molded Dual-In-Line Package
Order Number LMC6042AIN or LMC6042IN
NS Package Number N08E
www.national.com
14
LMC6042 CMOS Dual Micropower Operational Amplifier
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
www.national.com
National Semiconductor
Europe Customer Support Center
Fax: +49 (0) 180-530 85 86
Email: europe.support@nsc.com
Deutsch Tel: +49 (0) 69 9508 6208
English Tel: +44 (0) 870 24 0 2171
Français Tel: +33 (0) 1 41 91 8790
National Semiconductor
Asia Pacific Customer
Support Center
Email: ap.support@nsc.com
National Semiconductor
Japan Customer Support Center
Fax: 81-3-5639-7507
Email: jpn.feedback@nsc.com
Tel: 81-3-5639-7560
