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LMV321 Single/ LMV358 Dual/ LMV324 Quad
General Purpose, Low Voltage, Rail-to-Rail Output
Operational Amplifiers
General Description
The LMV358/324 are low voltage (2.7–5.5V) versions of the
dual and quad commodity op amps, LM358/324, which currently operate at 5–30V. The LMV321 is the single version.
The LMV321/358/324 are the most cost effective solutions
for the applications where low voltage operation, space saving and low price are needed. They offer specifications that
meet or exceed the familiar LM358/324. The
LMV321/358/324 haverail-to-railoutput swing capability and
the input common-mode voltage range includes ground.
They all exhibit excellent speed-power ratio, achieving
1 MHz of bandwidth and 1 V/µs of slew rate with low supply
current.
The LMV321 is available in space saving SC70-5, which is
approximately half the size of SOT23-5. The small package
saves space on pc boards, and enables the design of small
portable electronic devices. It also allows the designer to
place the device closer to the signal source to reduce noise
pickup and increase signal integrity.
The chips are built with National’s advanced submicron
silicon-gate BiCMOS process. The LMV321/358/324 have
bipolar input and output stages for improved noise performance and higher output current drive.
Features
(For V
+
=
5V and V
−
=
0V,Typical Unless Otherwise Noted)
n Guaranteed 2.7V and 5V Performance
n No Crossover Distortion
n Space Saving Package SC70-5 2.0x2.1x1.0mm
n Industrial Temp.Range −40˚C to +85˚C
n Gain-Bandwidth Product 1MHz
n Low Supply Current
LMV321 130µA
LMV358 210µA
LMV324 410µA
n Rail-to-Rail Output Swing
@
10kΩ Load V+−10mV
V
−
+65mV
n V
CM
−0.2V to V+−0.8V
Applications
n Active Filters
n General Purpose Low Voltage Applications
n General Purpose Portable Devices
Connection Diagrams
5-Pin SC70-5/SOT23-5
DS100060-1
Top View
8-Pin SO/MSOP
DS100060-2
Top View
14-Pin SO/TSSOP
DS100060-3
Top View
August 1999
LMV321 Single/ LMV358 Dual/ LMV324 Quad General Purpose, Low Voltage, Rail-to-Rail Output
Operational Amplifiers
© 1999 National Semiconductor Corporation DS100060 www.national.com
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Ordering Information
Package
Temperature Range
Packaging Marking Transport Media NSC DrawingIndustrial
−40˚C to +85˚C
5-Pin SC70-5 LMV321M7 A12 1k Units Tape and Reel MAA05
LMV321M7X A12 3k Units Tape and Reel
5-Pin SOT23-5 LMV321M5 A13 1k Units Tape and Reel MA05B
LMV321M5X A13 3k Units Tape and Reel
8-Pin Small Outline LMV358M LMV358M Rails
M08A
LMV358MX LMV358M 2.5k Units Tape and Reel
8-Pin MSOP LMV358MM LMV358 1k Units Tape and Reel
MUA08A
LMV358MMX LMV358 3.5k Units Tape and Reel
14-Pin Small Outline LMV324M LMV324M Rails
M14A
LMV324MX LMV324M 2.5k Units Tape and Reel
14-Pin TSSOP LMV324MT LMV324MT Rails
MTC14
LMV324MTX LMV324MT 2.5k Units Tape and Reel
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Page 3
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)
Machine Model 100V
Human Body Model
LMV358/324 2000V
LMV321 900V
Differential Input Voltage
±
Supply Voltage
Supply Voltage (V
+–V−
) 5.5V
Output Short Circuit to V
+
(Note 3)
Output Short Circuit to V
−
(Note 4)
Soldering Information
Infrared or Convection (20 sec) 235˚C
Storage Temp. Range −65˚C to 150˚C
Junction Temp. (T
j
, max) (Note 5) 150˚C
Operating Ratings (Note 1)
Supply Voltage 2.7V to 5.5V
Temperature Range
LMV321, LMV358, LMV324 −40˚C≤T
J
≤85˚C
Thermal Resistance (θ
JA
)(Note 10)
5-pin SC70-5 478˚C/W
5-pin SOT23-5 265˚C/W
8-Pin SOIC 190˚C/W
8-Pin MSOP 235˚C/W
14-Pin SOIC 145˚C/W
14-Pin TSSOP 155˚C/W
2.7V DC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ= 25˚C, V+= 2.7V, V−= 0V, VCM= 1.0V, VO=V+/2 and R
L
>
1MΩ.
Symbol Parameter Conditions Typ
(Note 6)
Limit
(Note 7)
Units
V
OS
Input Offset Voltage 1.7 7 mV
max
TCV
OS
Input Offset Voltage Average
Drift
5 µV/˚C
I
B
Input Bias Current 11 250 nA
max
I
OS
Input Offset Current 5 50 nA
max
CMRR Common Mode Rejection Ratio 0V ≤ V
CM
≤ 1.7V 63 50 dB
min
PSRR Power Supply Rejection Ratio 2.7V ≤ V
+
≤ 5V
V
O
=1V
60 50 dB
min
V
CM
Input Common-Mode Voltage
Range
For CMRR≥50dB −0.2 0 V
min
1.9 1.7 V
max
V
O
Output Swing RL= 10kΩ to 1.35V V+-10 V+-100 mV
min
60 180 mV
max
I
S
Supply Current LMV321 80 170 µA
max
LMV358
Both amplifiers
140 340 µA
max
LMV324
All four amplifiers
260 680 µA
max
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Page 4
2.7V AC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ= 25˚C, V+= 2.7V, V−= 0V, VCM= 1.0V, VO=V+/2 and R
L
>
1MΩ.
Symbol Parameter Conditions
Typ
(Note 6)
Limit
(Note 7)
Units
GBWP Gain-Bandwidth Product C
L
= 200 pF 1 MHz
Φ
m
Phase Margin 60 Deg
G
m
Gain Margin 10 dB
e
n
Input-Referred Voltage Noise f = 1 kHz 46
i
n
Input-Referred Current Noise f = 1 kHz 0.17
5V DC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ= 25˚C, V+= 5V, V−= 0V, VCM= 2.0V, VO=V+/2 and R
L
>
1MΩ.
Boldface limits apply at the temperature extremes.
Symbol Parameter Conditions Typ
(Note 6)
Limit
(Note 7)
Units
V
OS
Input Offset Voltage 1.7 7
9
mV
max
TCV
OS
Input Offset Voltage Average
Drift
5 µV/˚C
I
B
Input Bias Current 15 250
500
nA
max
I
OS
Input Offset Current 5 50
150
nA
max
CMRR Common Mode Rejection Ratio 0V ≤ V
CM
≤ 4V 65 50 dB
min
PSRR Power Supply Rejection Ratio 2.7V ≤ V
+
≤ 5V
V
O
=1VVCM=1V
60 50 dB
min
V
CM
Input Common-Mode Voltage
Range
For CMRR≥50dB −0.2 0 V
min
4.2 4 V
max
A
V
Large Signal Voltage Gain
(Note 8)
RL=2kΩ 100 15
10
V/mV
min
V
O
Output Swing RL=2kΩto 2.5V V+-40 V+-300
V
+
-400
mV
min
120 300
400
mV
max
R
L
= 10kΩ to 2.5V V+-10 V+-100
V
+
-200
mV
min
65 180
280
mV
max
I
O
Output Short Circuit Current Sourcing, VO=0V 60 5 mA
min
Sinking, V
O
= 5V 160 10 mA
min
I
S
Supply Current LMV321 130 250
350
µA
max
LMV358
Both amplifiers
210 440
615
µA
max
LMV324
All four amplifiers
410 830
1160
µA
max
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Page 5
5V AC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for TJ= 25˚C, V+= 5V, V−= 0V, VCM= 2.0V, VO=V+/2 and R
L
>
1MΩ.
Boldface limits apply at the temperature extremes.
Symbol Parameter Conditions
Typ
(Note 6)
Limit
(Note 7)
Units
SR Slew Rate (Note 9) 1 V/µs
GBWP Gain-Bandwidth Product C
L
= 200 pF 1 MHz
Φ
m
Phase Margin 60 Deg
G
m
Gain Margin 10 dB
e
n
Input-Referred Voltage Noise f = 1 kHz, 39
i
n
Input-Referred Current Noise f = 1 kHz 0.21
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 kΩ in series with 100 pF. Machine model, 0Ω in series with 200 pF.
Note 3: Shorting output to V
+
will adversely affect reliability.
Note 4: Shorting output to V
-
will adversely affect reliability.
Note 5: The maximum power dissipation is a function of T
J(max)
, θJA, and TA. The maximum allowable power dissipation at any ambient temperature is PD=
(T
J(max)–TA
)/θJA. All numbers apply for packages soldered directly into a PC board.
Note 6: Typical values represent the most likely parametric norm.
Note 7: All limits are guaranteed by testing or statistical analysis.
Note 8: R
L
is connected to V-. The output voltage is 0.5V ≤ VO≤ 4.5V.
Note 9: Connected as voltage follower with 3V step input. Number specified is the slower of the positive and negative slew rates.
Note 10: All numbers are typical, and apply for packages soldered directly onto a PC board in still air.
Typical Performance Characteristics Unless otherwise specified, V
S
= +5V, single supply, TA= 25˚C.
Supply Current vs Supply
Voltage (LMV321)
DS100060-73
Input Current vs
Temperature
DS100060-A9
Sourcing Current vs
Output Voltage
DS100060-69
Sourcing Current vs
Output Voltage
DS100060-68
Sinking Current vs
Output Voltage
DS100060-70
Sinking Current vs
Output Voltage
DS100060-71
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Page 6
Typical Performance Characteristics Unless otherwise specified, V
S
= +5V, single supply,
T
A
= 25˚C. (Continued)
Output Voltage Swing
vs Supply Voltage
DS100060-67
Input Voltage Noise vs Frequency
DS100060-56
Input Current Noise vs Frequency
DS100060-60
Input Current Noise vs Frequency
DS100060-58
Crosstalk Rejection vs Frequency
DS100060-61
PSRR vs Frequency
DS100060-51
CMRR vs Frequency
DS100060-62
CMRR vs Input
Common Mode Voltage
DS100060-64
CMRR vs Input
Common Mode Voltage
DS100060-63
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Page 7
Typical Performance Characteristics Unless otherwise specified, V
S
= +5V, single supply,
T
A
= 25˚C. (Continued)
∆ V
OS
vs CMR
DS100060-53
∆ VOSvs CMR
DS100060-50
Input Voltage vs
Output Voltage
DS100060-54
Input Voltage vs
Output Voltage
DS100060-52
Open Loop
Frequency Response
DS100060-42
Open Loop
Frequency Response
DS100060-41
Open Loop Frequency
Response vs Temperature
DS100060-43
Gain and Phase vs
Capacitive Load
DS100060-45
Gain and Phase vs
Capacitive Load
DS100060-44
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Page 8
Typical Performance Characteristics Unless otherwise specified, V
S
= +5V, single supply,
T
A
= 25˚C. (Continued)
Slew Rate vs
Supply Voltage
DS100060-57
Non-Inverting Large
Signal Pulse Response
DS100060-88
Non-Inverting Large
Signal Pulse Response
DS100060-A1
Non-Inverting Large
Signal Pulse Response
DS100060-A0
Non-Inverting Small
Signal Pulse Response
DS100060-89
Non-Inverting Small
Signal Pulse Response
DS100060-A2
Non-Inverting Small
Signal Pulse Response
DS100060-A3
Inverting Large Signal
Pulse Response
DS100060-90
Inverting Large Signal
Pulse Response
DS100060-A4
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Page 9
Typical Performance Characteristics Unless otherwise specified, V
S
= +5V, single supply,
T
A
= 25˚C. (Continued)
Inverting Large Signal
Pulse Response
DS100060-A5
Inverting Small Signal
Pulse Response
DS100060-91
Inverting Small Signal
Pulse Response
DS100060-A6
Inverting Small Signal
Pulse Response
DS100060-A7
Stability vs Capacitive Load
DS100060-46
Stability vs Capacitive Load
DS100060-47
Stability vs Capacitive Load
DS100060-49
Stability vs Capacitive Load
DS100060-48
THD vs Frequency
DS100060-59
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Page 10
Typical Performance Characteristics Unless otherwise specified, V
S
= +5V, single supply,
T
A
= 25˚C. (Continued)
Application Notes
1.0 Benefits of the LMV321/358/324
Size. The small footprints of the LMV321/358/324 packages
save space on printed circuit boards, and enable the design
of smaller electronic products, such as cellular phones, pagers, or other portable systems. The low profile of the
LMV321/358/324 make them possible to use in PCMCIA
type III cards.
Signal Integrity.Signals can pick up noise between the signal source and the amplifier. By using a physically smaller
amplifier package, the LMV321/358/324 can be placed
closer to the signal source, reducing noise pickup and increasing signal integrity.
Simplified Board Layout. These products help you to avoid
using long pc traces inyour pc board layout. This means that
no additional components, such as capacitors and resistors,
are needed to filter out the unwanted signals due to the interference between the long pc traces.
Low Supply Current. These devices will help you to maximize battery life. They are ideal for battery powered systems.
Low Supply Voltage. National provides guaranteed performance at 2.7V and 5V. These guarantees ensure operation
throughout the battery lifetime.
Rail-to-Rail Output. Rail-to-rail output swing provides maximum possible dynamic range at the output. This is particularly important when operating on low supply voltages.
Input Includes Ground. Allows direct sensing near GND in
single supply operation.
The differential input voltage may be larger than V
+
without
damaging the device. Protection should be provided to prevent the input voltages from going negative more than −0.3V
(at 25˚C).An input clamp diode with a resistor to the IC input
terminal can be used.
Ease of Use & No Crossover Distortion. The LMV321/
358/324 offer specifications similar to the familiar LM324. In
addition, the new LMV321/358/324 effectively eliminate the
output crossover distortion. The scope photos in
Figure 1
and
Figure 2
compare the output swing of the LMV324 and
the LM324 in a voltage follower configuration, with V
S
=
±
2.5V and RL(=2kΩ) connected to GND. It is apparent that
the crossover distortion has been eliminated in the new
LMV324.
2.0 Capacitive Load Tolerance
The LMV321/358/324 can directly drive 200 pF in unity-gain
without oscillation. The unity-gain follower is the most sensitive configuration to capacitive loading. Direct capacitive
loading reduces the phase margin of amplifiers. The combination of the amplifier’s output impedance and thecapacitive
load induces phase lag. This results in either an underdamped pulse response or oscillation. To drive a heavier capacitive load, circuit in
Figure 3
can be used.
Open Loop Output
Impedance vs Frequency
DS100060-55
Short Circuit Current
vs Temperature (Sinking)
DS100060-65
Short Circuit Current
vs Temperature (Sourcing)
DS100060-66
Time (50µs/div)
Output Voltage (500mV/div)
DS100060-97
FIGURE 1. Output Swing of LMV324
Output Voltage (500mV/div)
Time (50µs/div)
DS100060-98
FIGURE 2. Output Swing of LM324
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Page 11
Application Notes (Continued)
In
Figure 3
, the isolation resistor R
ISO
and the load capacitor
C
L
form a pole to increase stability by adding more phase
margin to the overall system. The desired performance depends on the value of R
ISO
. The bigger the R
ISO
resistor
value, the more stable Vout will be.
Figure 4
is an output
waveform of
Figure 3
using 620Ω for R
ISO
and 510 pF for
C
L.
.
The circuit in
Figure 5
is an improvement to the one in
Figure
3
because it provides DC accuracy as well as AC stability. If
there were a load resistor in
Figure 3
, the output would be
voltage divided by R
ISO
and the load resistor. Instead, in
Fig-
ure 5
,RFprovides the DC accuracy by using feed-forward
techniques to connect V
IN
to RL. Caution is needed in choos-
ing the value of R
F
due to the input bias current of the
LMV321/358/324. C
F
and R
ISO
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. Increased capacitive drive is possible by increasing the
value of C
F
. This in turn will slow down the pulse response.
3.0 Input Bias Current Cancellation
The LMV321/358/324 family has a bipolar input stage. The
typical input bias current of LMV321/358/324 is 15 nA with
5V supply.Thus a 100 kΩ input resistor will cause 1.5 mV of
error voltage. By balancing the resistor values at both inverting and non-inverting inputs, the error caused by the amplifier’s input bias current will be reduced. The circuit in
Figure
6
shows how to cancel the error caused by input bias
current.
4.0 Typical Single-Supply Application Circuits
4.1 Difference Amplifier
The difference amplifier allows the subtraction of two voltages or, as a special case, the cancellation of a signal common totwo inputs. It is useful as a computational amplifier,in
making a differential to single-ended conversion or in rejecting a common mode signal.
DS100060-4
FIGURE 3. Indirectly Driving A Capacitive Load Using
Resistive Isolation
Time (2µs/div)
Output Signal Input Signal
(1v/div)
DS100060-99
FIGURE 4. Pulse Response of the LMV324 Circuit in
Figure 3
DS100060-5
FIGURE 5. Indirectly Driving A Capacitive Load with
DC Accuracy
DS100060-6
FIGURE 6. Cancelling the Error Caused by Input Bias
Current
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Page 12
Application Notes (Continued)
4.2 Instrumentation Circuits
The input impedance of the previous difference amplifier is
set by the resistors R
1,R2,R3
, and R4. To eliminate the
problems of low input impedance, one way is to use a voltage follower ahead of each input as shown in the following
two instrumentation amplifiers.
4.2.1 Three-op-amp Instrumentation Amplifier
The quad LMV324 can be used to build a three-op-amp instrumentation amplifier as shown in
Figure 8
.
The first stage of this instrumentation amplifier is a
differential-input, differential-output amplifier, with two voltage followers. These two voltage followers assure that the
input impedance is over 100 MΩ. The gain of this instrumentation amplifier is set by the ratio of R
2/R1.R3
should equal
R
1
, and R4equal R2. Matching of R3to R1and R4to R2affects the CMRR. For good CMRR over temperature, low drift
resistors should be used. Making R
4
slightly smaller than R
2
and addinga trim pot equal to twice the difference between
R
2
and R4will allow the CMRR to be adjusted for optimum.
4.2.2 Two-op-amp Instrumentation Amplifier
A two-op-amp instrumentation amplifier can also be used to
make a high-input-impedance dc differential amplifier (
Fig-
ure 9
) . As in the three-op-amp circuit, this instrumentation
amplifier requires precise resistor matching for good CMRR.
R4 should equal to R1 and R3 should equal R2.
4.3 Single-Supply Inverting Amplifier
There may be cases where the input signal going into the
amplifier is negative. Because the amplifier is operating in
single supply voltage, a voltage divider using R
3
and R4is
implemented to bias the amplifier so the input signal is within
the input common-mode voltage range of the amplifier. The
capacitor C
1
is placed between the inverting input and resis-
tor R
1
to block the DC signal going into theAC signal source,
V
IN
. The values of R1and C1affect the cutoff frequency, fc
= 1/2πR
1C1
.
As a result, the output signal is centered around mid-supply
(if the voltage divider provides V
+
/2 at the non-inverting input). The output can swing to both rails, maximizing the
signal-to-noise ratio in a low voltage system.
4.4 Active Filter
4.4.1 Simple Low-Pass Active Filter
The simple low-pass filter is shown in
Figure 11
. Its low-
frequency gain (ω→0) is defined by -R
3/R1
. This allows lowfrequency gains other than unity to be obtained. The filter
has a -20dB/decade roll-off after its corner frequency fc. R
2
should be chosen equal to the parallel combination of R1and
R
3
to minimize errors due to bias current. The frequency re-
sponse of the filter is shown in
Figure 12
.
DS100060-7
DS100060-19
FIGURE 7. Difference Amplifier
DS100060-85
FIGURE 8. Three-op-amp Instrumentation Amplifier
DS100060-11
DS100060-35
FIGURE 9. Two-Op-amp Instrumentation Amplifier
DS100060-13
DS100060-20
FIGURE 10. Single-Supply Inverting Amplifier
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Page 13
Application Notes (Continued)
Note that the single-op-amp active filters are used in to the
applications that require low quality factor, Q( ≤ 10), low frequency (≤ 5 kHz), and low gain (≤ 10), or a small value for
the product of gain times Q (≤ 100). The op amp should have
an open loop voltage gain at the highest frequency of interest at least 50 times larger than the gain of the filter at this
frequency. In addition, the selected op amp should have a
slew rate that meets the following requirement:
SlewRate ≥ 0.5x(ω
HVOPP
)x10−6V/µsec
where ω
H
is the highest frequency of interest, and V
opp
is the
output peak-to-peak voltage.
4.4.2 Sallen-Key 2nd-Order Active Low-Pass Filter
The Sallen-Key 2nd-order active low-pass filter is illustrated
in
Figure 13
. The dc gain of the filter is expressed as
(1)
Its transfer function is
(2)
The following paragraphs explain how to select values for
R
1,R2,R3,R4,C1
, and C2for given filter requirements, such
as A
LP
, Q, and fc.
The standard form for a 2nd-order low pass filter is
(3)
where
Q: Pole Quality Factor
ω
C
: Corner Frequency
Comparison between the
Equation (2)
and
Equation (3)
yields
(4)
(5)
To reduce the required calculations in filter design, it is convenient to introduce normalization into the components and
design parameters. To normalize, let ω
C
= ωn= 1rad/s, and
C
1=C2=Cn
= 1F, and substitute these values into
Equation
(4)
and
Equation (5)
. From
Equation (4)
, we obtain
(6)
From
Equation (5)
, we obtain
(7)
For minimum dc offset, V+ = V-, the resistor values at both
inverting and non-inverting inputs should be equal, which
means
(8)
From
Equation (1)
and
Equation (8)
, we obtain
(9)
DS100060-14
DS100060-37
FIGURE 11. Simple Low-Pass Active Filter
DS100060-15
FIGURE 12. Frequency Response of Simple Low-Pass
Active Filter in Figure 11
DS100060-16
FIGURE 13. Sallen-Key 2nd-Order Active Low-Pass
Filter
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Page 14
Application Notes (Continued)
(10)
The values of C
1
and C2are normally close to or equal to
As a design example:
Require: A
LP
=2,Q=1,fc=1KHz
Start by selecting C1 and C2. Choose a standard value that
is close to
From
Equations (6), (7), (9), (10)
,
R
1
=1Ω
R
2
=1Ω
R
3
=4Ω
R
4
=4Ω
The above resistor values are normalized values with
ω
n
=1rad/s and C1=C2=Cn= 1F. To scale the normalized
cut-off frequency and resistances to the real values, two
scaling factors are introduced, frequency scaling factor (k
f
)
and impedance scaling factor (k
m
).
Scaled values:
R
2=R1
= 15.9 kΩ
R
3=R4
= 63.6 kΩ
C
1=C2
= 0.01 µF
An adjustment to the scaling may be made in order to have
realistic values for resistors and capacitors. The actual value
used for each component is shown in the circuit.
4.4.3 2nd-order High Pass Filter
A 2nd-order high pass filter can be built by simply interchanging those frequency selective components (R
1,R2
,
C
1,C2
) in the Sallen-Key 2nd-order active low pass filter.As
shown in
Figure 14
, resistors become capacitors, and capacitors become resistors. The resulted high pass filter has
the same corner frequency and the same maximum gain as
the previous 2nd-order low pass filter if the same components are chosen.
4.4.4 State Variable Filter
A state variable filter requires three op amps. One convenient way to build state variable filters is with a quad op amp,
such as the LMV324 (
Figure 15
).
This circuit can simultaneously represent a low-pass filter,
high-pass filter, and bandpass filter at threedifferent outputs.
The equations for these functions are listed below. It is also
called ″Bi-Quad″ active filter as it can produce a transfer
function which is quadratic in both numerator and
denominator.
DS100060-83
FIGURE 14. Sallen-Key 2nd-Order Active High-Pass
Filter
DS100060-39
FIGURE 15. State Variable Active Filter
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Page 15
Application Notes (Continued)
where for all three filters,
(11)
(12)
A design example for a bandpass filter is shown below:
Assume the system design requires a bandpass filter with f
O
= 1 kHz and Q = 50. What needs tobe calculated are capacitor and resistor values.
First choose convenient values for C
1,R1
and R2:
C
1
= 1200 pF
2R2=R
1
=30kΩ
Then from
Equation (11)
,
From
Equation (12)
,
From the above calculated values, the midband gain is H0=
R
3/R2
= 100 (40dB). The nearest 5%standard values have
been added to
Figure 15
.
4.5 Pulse Generators and Oscillators
A pulse generator is shown in
Figure 16
. Two diodes have
been used to separatethe charge and discharge pathsto capacitor C.
When the output voltage V
O
is first at its high, VOH, the ca-
pacitor C is charged toward V
OH
through R2. The voltage
across C rises exponentially with a time constant τ =R
2
C,
and this voltage is applied to the inverting input of the op
amp. Meanwhile, the voltage at the non-inverting input is set
at the positive threshold voltage (V
TH+
) of the generator. The
capacitor voltage continually increases until it reaches V
TH+
,
at which point the output of the generator will switch to its
low, V
OL
(=0V in this case). The voltage at the non-inverting
input is switched to the negative threshold voltage (V
TH-
)of
the generator. The capacitor then starts to discharge toward
V
OL
exponentially through R1, with a time constant τ =R1C.
When the capacitor voltage reaches V
TH-
, the output of the
pulse generator switches to V
OH
. The capacitor starts to
charge, and the cycle repeats itself.
DS100060-81
FIGURE 16. Pulse Generator
www.national.com15
Page 16
Application Notes (Continued)
As shown in the waveforms in
Figure 17
, the pulse width (T1)
is set by R
2
, C and VOH, and the time between pulses (T2)is
set by R
1
, C and VOL. This pulse generator can be made to
have different frequencies and pulse width by selecting different capacitor value and resistor values.
Figure 18
shows another pulse generator, with separate
charge and discharge paths. The capacitor is charged
through R1 and is discharged through R
2
.
Figure 19
is a squarewave generator with the same path for
charging and discharging the capacitor.
4.6 Current Source and Sink
The LMV321/358/324 can be used in feedback loops which
regulate the current in external PNP transistors to provide
current sources or in external NPN transistors to provide current sinks.
4.6.1 Fixed Current Source
A multiple fixed current source is show in
Figure 20
. A volt-
age (V
REF
= 2V) is established acrossresistor R3by the volt-
age divider (R
3
and R4). Negative feedback is used to cause
the voltage drop across R
1
to be equal to V
REF
.This controls
the emitter current of transistor Q
1
and if we neglect the base
current of Q
1
and Q2, essentially this same current is avail-
able out of the collector of Q
1
.
Large input resistors can be used to reduce current loss and
a Darlington connection can be used to reduce errors due to
the β of Q
1
.
The resistor,R
2
, can be used to scale the collector current of
Q
2
either above or below the 1 mA reference value.
DS100060-86
FIGURE 17. Waveforms of the Circuit in Figure 16
DS100060-77
FIGURE 18. Pulse Generator
DS100060-76
FIGURE 19. Squarewave Generator
DS100060-80
FIGURE 20. Fixed Current Source
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Page 17
Application Notes (Continued)
4.6.2 High Compliance Current Sink
A current sink circuit is shown in
Figure 21
. The circuit re-
quires only one resistor (R
E
) and supplies an output current
which is directly proportional to this resistor value.
4.7 Power Amplifier
A power amplifier is illustrated in
Figure 22
. This circuit can
provide a higher output current because a transistor follower
is added to the output of the op amp.
4.8 LED Driver
The LMV321/358/324 can beused to drive an LEDas shown
in
Figure 23
.
4.9 Comparator with Hysteresis
The LMV321/358/324 can be used as a low power comparator.
Figure 24
shows a comparator with hysteresis. The hys-
teresis is determined by the ratio of the two resistors.
V
TH+
=
V
REF
/(1+R1/R2)+VOH/(1+R2/R1)
V
TH−
=
V
REF
/(1+R1/R2)+VOL/(1+R2/R1)
V
H
=
(V
OH−VOL
)/(1+R2/R1)
where
V
TH+
: Positive Threshold Voltage
V
TH−
: Negative Threshold Voltage
V
OH
: Output Voltage at High
V
OL
: Output Voltage at Low
V
H
: Hysteresis Voltage
Since LMV321/358/324 have rail-to-rail output, the
(V
OH−VOL
) equals to VS, which is the supply voltage.
V
H
=
V
S
/(1+R2/R1)
The differential voltage at the input of the op amp should not
exceed the specified absolute maximum ratings. For real
comparators that are much faster, we recommend you to use
National’s LMV331/393/339, which aresingle, dual and quad
general purpose comparators for low voltage operation.
DS100060-82
FIGURE 21. High Compliance Current Sink
DS100060-79
FIGURE 22. Power Amplifier
DS100060-84
FIGURE 23. LED Driver
DS100060-78
FIGURE 24. Comparator with Hysteresis
www.national.com17
Page 18
SC70-5 Tape and Reel Specification
SOT-23-5 Tape and Reel Specification
TAPE FORMAT
Tape Section
#
Cavities Cavity Status Cover Tape Status
Leader 0 (min) Empty Sealed
(Start End) 75 (min) Empty Sealed
Carrier 3000 Filled Sealed
250 Filled Sealed
Trailer 125 (min) Empty Sealed
(Hub End) 0 (min) Empty Sealed
DS100060-B3
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Page 19
SOT-23-5 Tape and Reel Specification (Continued)
TAPE DIMENSIONS
8 mm 0.130 0.124 0.130 0.126 0.138±0.002 0.055±0.004 0.157 0.315±0.012
(3.3) (3.15) (3.3) (3.2) (3.5
±
0.05) (1.4±0.11) (4) (8±0.3)
Tape Size DIM A DIM Ao DIM B DIM Bo DIM F DIM Ko DIM P1 DIM W
DS100060-B1
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Page 20
SOT-23-5 Tape and Reel Specification (Continued)
REEL DIMENSIONS
8 mm 7.00 0.059 0.512 0.795 2.165 0.331 + 0.059/−0.000 0.567 W1+ 0.078/−0.039
330.00 1.50 13.00 20.20 55.00 8.40 + 1.50/−0.00 14.40 W1 + 2.00/−1.00
Tape Size A B C D N W1 W2 W3
DS100060-B2
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Page 21
Physical Dimensions inches (millimeters) unless otherwise noted
5-Pin SC70-5 Tape and Reel
Order Number LMV321M7 and LMV321M7X
NS Package Number MAA05A
www.national.com21
Page 22
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
5-Pin SOT23-5 Tape and Reel
Order Number LMV321M5 and LMV321M5X
NS Package Number MA05B
www.national.com 22
Page 23
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
8-Pin Small Outline
Order Number LMV358M and LMV358MX
NS Package Number M08A
www.national.com23
Page 24
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
8-Pin MSOP
Order Number LMV358MM and LMV358MMX
NS Package Number MUA08A
www.national.com 24
Page 25
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
14-Pin Small Outline
Order Number LMV324M and LMV324MX
NS Package Number M14A
www.national.com25
Page 26
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
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.
National Semiconductor
Corporation
Americas
Tel: 1-800-272-9959
Fax: 1-800-737-7018
Email: support@nsc.com
National Semiconductor
Europe
Fax: +49 (0) 1 80-530 85 86
Email: europe.support@nsc.com
Deutsch Tel: +49 (0) 1 80-530 85 85
English Tel: +49 (0) 1 80-532 78 32
Français Tel: +49 (0) 1 80-532 93 58
Italiano Tel: +49 (0) 1 80-534 16 80
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Asia Pacific Customer
Response Group
Tel: 65-2544466
Fax: 65-2504466
Email: sea.support@nsc.com
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Japan Ltd.
Tel: 81-3-5639-7560
Fax: 81-3-5639-7507
www.national.com
14-Pin TSSOP
Order Number LMV324MT and LMV324MTX
NS Package Number MTC14
LMV321 Single/ LMV358 Dual/ LMV324 Quad General Purpose, Low Voltage, Rail-to-Rail Output
Operational Amplifiers
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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