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LMC6034
CMOS Quad Operational Amplifier
General Description
The LMC6034 is a CMOS quad operational amplifier which
can operate from either a single supply or dual supplies. Its
performance features include an input common-mode range
that reaches ground, low input bias current, and high voltage
gain into realistic loads, such as 2 kΩ and 600Ω.
This chip is built with National’s advanced Double-Poly
Silicon-Gate CMOS process.
See the LMC6032 datasheet for a CMOS dual operational
amplifier with these same features. For higher performance
characteristics refer to the LMC660.
Features
n Specified for 2 kΩ and 600Ω loads
n High voltage gain: 126 dB
n
n
n
n
n
n
n
n
Low offset voltage drift: 2.3 µV/˚C
Ultra low input bias current: 40 fA
Input common-mode range includes V−
Operating Range from +5V to +15V supply
ISS = 400 µA/amplifier; independent of V+
Low distortion: 0.01% at 10 kHz
Slew rate: 1.1 V/µs
Improved performance over TLC274
Applications
n
n
n
n
n
High-impedance buffer or preamplifier
Current-to-voltage converter
Long-term integrator
Sample-and-hold circuit
Medical instrumentation
Connection Diagram
14-Pin DIP/SO
01113401
Top View
Guard Ring Connections
Non-Inverting Amplifier
01113408
© 2004 National Semiconductor Corporation
DS011134
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LMC6034 CMOS Quad Operational Amplifier
August 2000
LMC6034
Absolute Maximum Ratings (Note 1)
Current at Input Pin
± 5 mA
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Current at Power Supply Pin
35 mA
Junction Temperature (Note 3)
150˚C
ESD Tolerance (Note 4)
1000V
± Supply Voltage
Differential Input Voltage
Supply Voltage (V+ − V−)
16V
Output Short Circuit to V+
(Note 10)
Output Short Circuit to V−
(Note 2)
Lead Temperature
(Soldering, 10 sec.)
Operating Ratings(Note 1)
Supply Voltage Range
260˚C
Storage Temperature Range
(Note 11)
Thermal Resistance (θJA), (Note 12)
(Note 3)
Voltage at Output/Input Pin
4.75V to 15.5V
Power Dissipation
−65˚C to +150˚C
Power Dissipation
−40˚C ≤ TJ ≤
+85˚C
Temperature Range
(V ) +0.3V, (V ) −0.3V
14-Pin DIP
85˚C/W
± 18 mA
14-Pin SO
115˚C/W
+
Current at Output Pin
−
DC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ = 25˚C. Boldface limits apply at the temperature extremes. V+ = 5V, V−
= GND = 0V, VCM = 1.5V, VOUT = 2.5V, and RL > 1M unless otherwise specified.
Symbol
Parameter
Conditions
Typical
(Note 5)
LMC6034I
Units
Limit
(Note 6)
VOS
∆VOS/∆T
Input Offset Voltage
1
Input Offset Voltage
9
mV
11
max
2.3
µV/˚C
Average Drift
IB
IOS
RIN
CMRR
+PSRR
−PSRR
Input Bias Current
0.04
Input Offset Current
AV
Common Mode
0V ≤ VCM ≤ 12V
Rejection Ratio
V+ = 15V
Positive Power Supply
5V ≤ V+ ≤ 15V
Rejection Ratio
VO = 2.5V
Negative Power Supply
0V ≤ V− ≤ −10V
83
83
94
max
pA
Input Common-Mode
V+ = 5V & 15V
Voltage Range
For CMRR ≥ 50 dB
RL = 2 kΩ (Note 7)
Sinking
min
63
dB
60
min
dB
−0.4
−0.1
V
0
max
V+ − 1.9
V+ − 2.3
V
V+ − 2.6
min
200
V/mV
2000
1000
250
2
dB
60
min
Sourcing
Sinking
63
70
500
RL = 600Ω (Note 7)
TeraΩ
74
Sourcing
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100
>1
Input Resistance
Large Signal Voltage Gain
max
0.01
Rejection Ratio
VCM
pA
200
100
min
90
V/mV
40
min
100
V/mV
75
min
50
V/mV
20
min
Symbol
Parameter
Conditions
Typical
(Note 5)
LMC6034I
Units
Limit
(Note 6)
VO
Output Voltage Swing
V+ = 5V
4.87
RL = 2 kΩ to 2.5V
0.10
V+ = 5V
4.61
RL = 600Ω to 2.5V
0.30
V+ = 15V
14.63
V+ = 5V
VO = 1.5V
3
min
0.63
V
0.75
max
0.55
max
12.50
V
12.00
min
1.45
V
1.75
max
40
All Four Amplifiers
3.80
13.90
39
(Note 10)
Supply Current
V
V
Sourcing, VO = 0V
IS
4.00
0.45
21
Sinking, VO = 13V
max
0.26
Sourcing, VO = 0V
V+ = 15V
V
0.35
V
22
Sinking, VO = 5V
min
0.25
min
0.79
Output Current
4.00
13.00
RL = 600Ω to 7.5V
IO
V
13.50
RL = 2 kΩ to 7.5V
V+ = 15V
4.20
1.5
13
mA
9
min
13
mA
9
min
23
mA
15
min
23
mA
15
min
2.7
mA
3.0
max
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LMC6034
Unless otherwise specified, all limits guaranteed for TJ = 25˚C. Boldface limits apply at the temperature extremes. V+ = 5V, V−
= GND = 0V, VCM = 1.5V, VOUT = 2.5V, and RL > 1M unless otherwise specified.
LMC6034
AC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ = 25˚C. Boldface limits apply at the temperature extremes. V+ = 5V, V−
= GND = 0V, VCM = 1.5V, VOUT = 2.5V, and RL > 1M unless otherwise specified.
Symbol
Parameter
Conditions
Typical
(Note 5)
LMC6034I
Units
Limit
(Note 6)
SR
Slew Rate
(Note 8)
1.1
0.8
V/µs
GBW
Gain-Bandwidth Product
1.4
MHz
φM
Phase Margin
50
Deg
GM
Gain Margin
0.4
min
17
dB
Amp-to-Amp Isolation
(Note 9)
130
dB
en
Input-Referred Voltage Noise
F = 1 kHz
22
in
Input-Referred Current Noise
F = 1 kHz
0.0002
THD
Total Harmonic Distortion
F = 10 kHz, AV = −10
RL = 2 kΩ, VO = 8 VPP
0.01
%
± 5V Supply
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the component may occur. Operating Ratings 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 and split-supply operation. Continuous short circuit operation at elevated ambient temperature and/or multiple Op Amp shorts
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 3: The maximum power dissipation is a function of TJ(max), θJA, TA. The maximum allowable power dissipation at any ambient temperature is PD =
(TJ(max)–TA)/θJA.
Note 4: Human body model, 100 pF discharged through a 1.5 kΩ resistor.
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 type face).
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 = 10 kΩ connected to V+/2. Each amp excited in turn with 1 kHz to produce VO = 13 VPP.
Note 10: Do not connect output to V+, when V+ is greater than 13V or reliability may be adversely affected.
Note 11: For operating at elevated temperatures the device must be derated based on the thermal resistance θJA with PD = (TJ − TA)/θJA.
Note 12: All numbers apply for packages soldered directly into a PC board.
Typical Performance Characteristics
VS = ± 7.5V, TA = 25˚C unless otherwise specified
Supply Current
vs Supply Voltage
Input Bias Current
01113424
01113423
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4
Output Characteristics
Current Sinking
(Continued)
Output Characteristics
Current Sourcing
01113425
01113427
Input Voltage Noise
vs Frequency
CMRR vs Frequency
01113428
01113429
Open-Loop Frequency
Response
Frequency Response
vs Capacitive Load
01113431
01113430
5
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LMC6034
Typical Performance Characteristics VS = ±7.5V, TA = 25˚C unless otherwise specified
LMC6034
Typical Performance Characteristics VS = ±7.5V, TA = 25˚C unless otherwise specified
Non-Inverting Large Signal
Pulse Response
(Continued)
Stability vs
Capacitive Load
01113433
01113432
Stability vs
Capacitive Load
01113403
01113434
FIGURE 1. LMC6034 Circuit Topology (Each Amplifier)
Note: Avoid resistive loads of less than 500Ω, as they may cause
instability.
The large signal voltage gain while sourcing is comparable
to traditional bipolar op amps, even with a 600Ω load. The
gain while sinking is higher than most CMOS op amps, due
to the additional gain stage; however, under heavy load
(600Ω) the gain will be reduced as indicated in the Electrical
Characteristics.
Compensating Input Capacitance
The high input resistance of the LMC6034 op amps allows
the use of large feedback and source resistor values without
losing gain accuracy due to loading. However, the circuit will
be especially sensitive to its layout when these large-value
resistors are used.
Every amplifier has some capacitance between each input
and AC ground, and also some differential capacitance between the inputs. When the feedback network around an
amplifier is resistive, this input capacitance (along with any
additional capacitance due to circuit board traces, the
socket, etc.) and the feedback resistors create a pole in the
feedback path. In the following General Operational Amplifier
circuit, Figure 2 the frequency of this pole is
Applications Hint
Amplifier Topolgy
The topology chosen for the LMC6034, shown in Figure 1, is
unconventional (compared to general-purpose op amps) in
that the traditional unity-gain buffer output stage is not used;
instead, the output is taken directly from the output of the
integrator, to allow a larger output swing. Since the buffer
traditionally delivers the power to the load, while maintaining
high op amp gain and stability, and must withstand shorts to
either rail, these tasks now fall to the integrator.
As a result of these demands, the integrator is a compound
affair with an embedded gain stage that is doubly fed forward
(via Cf and Cff) by a dedicated unity-gain compensation
driver. In addition, the output portion of the integrator is a
push-pull configuration for delivering heavy loads. While
sinking current the whole amplifier path consists of three
gain stages with one stage fed forward, whereas while
sourcing the path contains four gain stages with two fed
forward.
where CS is the total capacitance at the inverting input,
including amplifier input capcitance and any stray capacitance from the IC socket (if one is used), circuit board traces,
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6
Note that these capacitor values are usually significantly
smaller than those given by the older, more conservative
formula:
(Continued)
etc., and RP is the parallel combination of RF and RIN. This
formula, as well as all formulae derived below, apply to
inverting and non-inverting op-amp configurations.
When the feedback resistors are smaller than a few kΩ, the
frequency of the feedback pole will be quite high, since CS is
generally less than 10 pF. If the frequency of the feedback
pole is much higher than the “ideal” closed-loop bandwidth
(the nominal closed-loop bandwidth in the absence of CS),
the pole will have a negligible effect on stability, as it will add
only a small amount of phase shift.
However, if the feedback pole is less than approximately 6 to
10 times the “ideal” −3 dB frequency, a feedback capacitor,
CF, should be connected between the output and the inverting input of the op amp. This condition can also be stated in
terms of the amplifier’s low-frequency noise gain: To maintain stability a feedback capacitor will probably be needed if
01113404
CS consists of the amplifier’s input capacitance plus any stray capacitance
from the circuit board and socket. CF compensates for the pole caused by
CS and the feedback resistors.
where
FIGURE 2. General Operational Amplifier Circuit
Using the smaller capacitors will give much higher bandwidth with little degradation of transient response. It may be
necessary in any of the above cases to use a somewhat
larger feedback capacitor to allow for unexpected stray capacitance, or to tolerate additional phase shifts in the loop, or
excessive capacitive load, or to decrease the noise or bandwidth, or simply because the particular circuit implementation needs more feedback capacitance to be sufficiently
stable. For example, a printed circuit board’s stray capacitance may be larger or smaller than the breadboard’s, so the
actual optimum value for CF may be different from the one
estimated using the breadboard. In most cases, the values
of CF should be checked on the actual circuit, starting with
the computed value.
is the amplifier’s low-frequency noise gain and GBW is the
amplifier’s gain bandwidth product. An amplifier’s lowfrequency noise gain is represented by the formula
regardless of whether the amplifier is being used in inverting
or non-inverting mode. Note that a feedback capacitor is
more likely to be needed when the noise gain is low and/or
the feedback resistor is large.
If the above condition is met (indicating a feedback capacitor
will probably be needed), and the noise gain is large enough
that:
Capacitive Load Tolerance
Like many other op amps, the LMC6034 may oscillate when
its applied load appears capacitive. The threshold of oscillation varies both with load and circuit gain. The configuration
most sensitive to oscillation is a unity-gain follower. See
Typical Performance Characteristics.
The load capacitance interacts with the op amp’s output
resistance to create an additional pole. If this pole frequency
is sufficiently low, it will degrade the op amp’s phase margin
so that the amplifier is no longer stable at low gains. As
shown in Figure 3, the addition of a small resistor (50Ω to
100Ω) in series with the op amp’s output, and a capacitor (5
pF to 10 pF) from inverting input to output pins, returns the
phase margin to a safe value without interfering with lowerfrequency circuit operation. Thus larger values of capacitance can be tolerated without oscillation. Note that in all
cases, the output will ring heavily when the load capacitance
is near the threshold for oscillation.
the following value of feedback capacitor is recommended:
If
the feedback capacitor should be:
7
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LMC6034
Applications Hint
LMC6034
Applications Hint
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, or perhaps a minor
(2:1) degradation of the amplifier’s performance. See Figures 6, 7, 8 for typical connections of guard rings for standard op-amp configurations. If both inputs are active and at
high impedance, the guard can be tied to ground and still
provide some protection; see Figure 9.
(Continued)
01113405
FIGURE 3. Rx, Cx Improve Capacitive Load Tolerance
Capacitive load driving capability is enhanced by using a pull
up resistor to V+ (Figure 4). Typically a pull up resistor
conducting 500 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).
01113406
FIGURE 5. Example of Guard Ring in P.C. Board
Layout
01113422
FIGURE 4. Compensating for Large Capacitive Loads
with a Pull Up Resistor
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 LMC6034, typically less
than 0.04 pA, it is essential to have an excellent layout.
Fortunately, the techniques for 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 LMC6034’s inputs and the
terminals of capacitors, diodes, conductors, resistors, relay
terminals, etc. connected to the op-amp’s inputs. See Figure
5. 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 an input. This
would cause a 100 times degradation from the LMC6034’s
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01113407
FIGURE 6. Guard Ring Connections
Inverting Amplifier
01113408
FIGURE 7. Guard Ring Connections
Non-Inverting Amplifier
8
(Continued)
BIAS CURRENT TESTING
The test method of Figure 11 is appropriate for bench-testing
bias current with reasonable accuracy. To understand its
operation, first close switch S2 momentarily. When S2 is
opened, then
01113409
FIGURE 8. Guard Ring Connections
Follower
01113412
01113410
FIGURE 11. Simple Input Bias Current Test Circuit
FIGURE 9. Guard Ring Connections
Howland Current Pump
A suitable capacitor for C2 would be a 5 pF or 10 pF silver
mica, NPO ceramic, or air-dielectric. When determining the
magnitude of Ib−, the leakage of the capacitor and socket
must be taken into account. Switch S2 should be left shorted
most of the time, or else the dielectric absorption of the
capacitor C2 could cause errors.
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
10.
Similarly, if S1 is shorted momentarily (while leaving S2
shorted)
where Cx is the stray capacitance at the + input.
01113411
(Input pins are lifted out of PC board and soldered directly to components.
All other pins connected to PC board.)
FIGURE 10. Air Wiring
9
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LMC6034
Applications Hint
LMC6034
Typical Single-Supply Applications
Sine-Wave Oscillator
(V+ = 5.0 VDC)
Additional single-supply applications ideas can be found in
the LM324 datasheet. The LMC6034 is pin-for-pin compatible with the LM324 and offers greater bandwidth and input
resistance over the LM324. These features will improve the
performance of many existing single-supply applications.
Note, however, that the supply voltage range of the
LMC6034 is smaller than that of the LM324.
Low-Leakage Sample-and-Hold
01113415
Oscillator frequency is determined by R1, R2, C1, and C2:
fosc = 1/2πRC, where R = R1 = R2 and
C = C1 = C2.
This circuit, as shown, oscillates at 2.0 kHz with a peak-topeak output swing of 4.0V.
01113413
Instrumentation Amplifier
1 Hz Square-Wave Oscillator
01113416
01113414
Power Amplifier
For good CMRR over temperature, low drift resistors should
be used. Matching of R3 to R6 and R4 to R7 affect CMRR.
Gain may be adjusted through R2. CMRR may be adjusted
through R7.
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01113417
10
LMC6034
Typical Single-Supply Applications
High Gain Amplifier with Offset
Voltage Reduction
(V+ = 5.0 VDC) (Continued)
10 Hz Bandpass Filter
01113418
fO = 10 Hz
Q = 2.1
Gain = −8.8
10 Hz High-Pass Filter
01113421
Gain = −46.8
Output offset
voltage reduced
to the level of
the input offset
voltage of the
bottom amplifier
(typically 1 mV).
01113420
fc = 10 Hz
d = 0.895
Gain = 1
2 dB passband ripple
1 Hz Low-Pass Filter
(Maximally Flat, Dual Supply Only)
01113419
fc = 1 Hz
d = 1.414
Gain = 1.57
11
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LMC6034
Ordering Information
Temperature Range
Package
NSC
Drawing
Transport
Media
14-Pin Small
Outline
M14A
Rail
Tape and Reel
Industrial−40˚C ≤ TJ ≤
+85˚
LMC6034IM
LMC6034IMX
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12
LMC6034 CMOS Quad Operational Amplifier
Physical Dimensions
inches (millimeters)
unless otherwise noted
Small Outline Dual-In-Line Pkg. (M)
Order Number LMC6034IM or LMC6034IMX
NS Package Number M14A
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.
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