LMV358-N [TI]
双路、5.5V、1MHz 运算放大器;
| 型号： | LMV358-N |
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TEXAS INSTRUMENTS |
| 描述： | 双路、5.5V、1MHz 运算放大器 放大器 运算放大器 放大器电路 |
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LMV321,LMV324,LMV358
LMV321/LMV358/LMV324 Single/Dual/Quad General Purpose, Low Voltage,
Rail-to-Rail Output Operational Amplifiers
Literature Number: SNOS012F
September 22, 2009
LMV321/LMV358/LMV324
Single/Dual/Quad
General Purpose, Low Voltage, Rail-to-Rail Output
Operational Amplifiers
General Description
Features
The LMV358/LMV324 are low voltage (2.7–5.5V) versions of
the dual and quad commodity op amps, LM358/LMV324,
which currently operate at 5–30V. The LMV321 is the single
version.
(For V+ = 5V and V− = 0V, unless otherwise specified)
Guaranteed 2.7V and 5V performance
No crossover distortion
Industrial temperature range
Gain-bandwidth product
■
■
−40°C to +85°C
■
■
■
The LMV321/LMV358/LMV324 are the most cost effective
solutions for the applications where low voltage operation,
space saving and low price are needed. They offer specifica-
tions that meet or exceed the familiar LM358/LMV324. The
LMV321/LMV358/LMV324 have rail-to-rail output swing ca-
pability and the input common-mode voltage range includes
ground. They all exhibit excellent speed to power ratio,
achieving 1 MHz of bandwidth and 1 V/µs of slew rate with
low supply current.
1 MHz
Low supply current
LMV321
LMV358
LMV324
—
—
—
130 μA
210 μA
410 μA
Rail-to-rail output swing @ 10 kΩ
V+ −10 mV
■
■
V− +65 mV
VCM
−0.2V to V+−0.8V
The LMV321 is available in the space saving 5-Pin SC70,
which is approximately half the size of the 5-Pin SOT23. 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.
Applications
Active filters
■
General purpose low voltage applications
General purpose portable devices
■
■
The chips are built with National's advanced submicron sili-
con-gate BiCMOS process. The LMV321/LMV358/LMV324
have bipolar input and output stages for improved noise per-
formance and higher output current drive.
Gain and Phase vs. Capacitive Load
Output Voltage Swing vs. Supply Voltage
10006045
10006067
© 2009 National Semiconductor Corporation
100060
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ꢀInfrared or Convection (30 sec)
Storage Temp. Range
Junction Temperature (Note 5)
260°C
−65°C to 150°C
150°C
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Operating Ratings (Note 1)
Supply Voltage
ESD Tolerance (Note 2)
Human Body Model
2.7V to 5.5V
Temperature Range (Note 5)
LMV321/LMV358/LMV324
LMV358/LMV324
LMV321
2000V
900V
−40°C to +85°C
Machine Model
100V Thermal Resistance (θ JA) (Note 10)
Differential Input Voltage
Input Voltage
Supply Voltage (V+–V −)
Output Short Circuit to V +
Output Short Circuit to V −
Soldering Information
±Supply Voltage
−0.3V to +Supply Voltage
5-pin SC70
5-pin SOT23
8-Pin SOIC
8-Pin MSOP
14-Pin SOIC
14-Pin TSSOP
478°C/W
265°C/W
190°C/W
235°C/W
145°C/W
155°C/W
5.5V
(Note 3)
(Note 4)
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 RL > 1 MΩ.
Symbol
Parameter
Conditions
Min
Typ
Max
Units
(Note 7)
(Note 6)
(Note 7)
VOS
Input Offset Voltage
1.7
5
7
mV
µV/°C
nA
TCVOS
IB
Input Offset Voltage Average Drift
Input Bias Current
11
5
250
50
IOS
Input Offset Current
nA
CMRR
Common Mode Rejection Ratio
50
50
63
dB
0V ≤ VCM ≤ 1.7V
2.7V ≤ V+ ≤ 5V
VO = 1V
PSRR
Power Supply Rejection Ratio
60
dB
VCM
VO
IS
Input Common-Mode Voltage Range
Output Swing
0
−0.2
1.9
V+ −10
V
For CMRR ≥ 50 dB
RL = 10 kΩ to 1.35V
LMV321
1.7
V
V+ −100
mV
mV
µA
60
180
170
340
Supply Current
80
LMV358
Both amplifiers
140
µA
µA
LMV324
All four amplifiers
260
680
2.7V AC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for T J = 25°C, V+ = 2.7V, V− = 0V, VCM = 1.0V, VO = V+/2 and RL > 1 MΩ.
Symbol
Parameter
Conditions
Min
Typ
Max
Units
(Note 7)
(Note 6)
(Note 7)
GBWP
Φm
Gain-Bandwidth Product
Phase Margin
CL = 200 pF
1
MHz
Deg
dB
60
10
46
Gm
Gain Margin
en
Input-Referred Voltage Noise
f = 1 kHz
f = 1 kHz
in
Input-Referred Current Noise
0.17
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2
5V DC Electrical Characteristics
Unless otherwise specified, all limits guaranteed for T J = 25°C, V+ = 5V, V− = 0V, VCM = 2.0V, VO = V+/2 and R L > 1 MΩ.
Boldface limits apply at the temperature extremes.
Symbol
Parameter
Conditions
Min
Typ
Max
Units
(Note 7)
(Note 6)
(Note 7)
VOS
Input Offset Voltage
1.7
7
9
mV
µV/°C
nA
TCVOS
IB
Input Offset Voltage Average Drift
Input Bias Current
5
15
250
500
IOS
Input Offset Current
5
50
150
nA
CMRR
PSRR
Common Mode Rejection Ratio
Power Supply Rejection Ratio
50
50
65
60
dB
dB
0V ≤ VCM ≤ 4V
2.7V ≤ V+ ≤ 5V
VO = 1V, VCM = 1V
VCM
Input Common-Mode Voltage
Range
0
−0.2
4.2
V
V
For CMRR ≥ 50 dB
4
AV
VO
Large Signal Voltage Gain
(Note 8)
15
10
V+ −300
V+ −400
100
RL = 2 kΩ
V/mV
mV
Output Swing
V+ −40
RL = 2 kΩ to 2.5V
120
300
400
mV
V+ −100
V+ −200
V+ −10
RL = 10 kΩ to 2.5V
mV
65
180
280
mV
IO
Output Short Circuit Current
Supply Current
Sourcing, VO = 0V
Sinking, VO = 5V
LMV321
5
60
mA
10
160
130
IS
250
350
µA
µA
µA
LMV358
Both amplifiers
210
410
440
615
LMV324
All four amplifiers
830
1160
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 > 1 MΩ.
Boldface limits apply at the temperature extremes.
Symbol
Parameter
Conditions
Min
Typ
Max
Units
(Note 7)
(Note 6)
(Note 7)
SR
Slew Rate
(Note 9)
1
1
V/µs
MHz
Deg
GBWP
Φm
Gain-Bandwidth Product
Phase Margin
CL = 200 pF
60
Gm
Gain Margin
10
39
dB
en
Input-Referred Voltage Noise
f = 1 kHz
f = 1 kHz
in
Input-Referred Current Noise
0.21
3
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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, applicable std. MIL-STD-883, Method 3015.7. Machine Model, applicable std. JESD22-A115-A (ESD MM std. of JEDEC)
Field-Induced Charge-Device Model, applicable std. JESD22-C101-C (ESD FICDM std. of JEDEC
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 TJ(MAX), θJA. The maximum allowable power dissipation at any ambient temperature
is PD = (TJ(MAX) – TA)/ θJA. All numbers apply for packages soldered directly onto a PC Board.
Note 6: Typical values represent the most likely parametric norm as determined at the time of characterization. Actual typical values may vary over time and will
also depend on the application and configuration. The typical values are not tested and are not guaranteed on shipped production material.
Note 7: All limits are guaranteed by testing or statistical analysis.
Note 8: RL 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.
Connection Diagrams
5-Pin SC70/SOT23
8-Pin SOIC/MSOP
14-Pin SOIC/TSSOP
10006001
Top View
10006002
Top View
10006003
Top View
Ordering Information
Temperature Range
Package
Packaging Marking
Transport Media
NSC Drawing
Industrial
−40°C to +85°C
LMV321M7
LMV321M7X
LMV321M5
LMV321M5X
LMV358M
1k Units Tape and Reel
3k Units Tape and Reel
1k Units Tape and Reel
3k Units Tape and Reel
Rails
5-Pin SC70
A12
MAA05A
MF05A
M08A
5-Pin SOT23
8-Pin SOIC
A13
LMV358M
LMV358
LMV324M
LMV324MT
LMV358MX
LMV358MM
LMV358MMX
LMV324M
2.5k Units Tape and Reel
1k Units Tape and Reel
3.5k Units Tape and Reel
Rails
8-Pin MSOP
14-Pin SOIC
14-Pin TSSOP
MUA08A
M14A
LMV324MX
LMV324MT
LMV324MTX
2.5k Units Tape and Reel
Rails
MTC14
2.5k Units Tape and Reel
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Typical Performance Characteristics Unless otherwise specified, VS = +5V, single supply,
TA = 25°C.
Supply Current vs. Supply Voltage (LMV321)
Input Current vs. Temperature
10006073
100060a9
Sourcing Current vs. Output Voltage
Sourcing Current vs. Output Voltage
10006069
10006068
Sinking Current vs. Output Voltage
Sinking Current vs. Output Voltage
10006070
10006071
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Output Voltage Swing vs. Supply Voltage
Input Voltage Noise vs. Frequency
10006056
10006067
Input Current Noise vs. Frequency
Input Current Noise vs. Frequency
10006060
10006058
Crosstalk Rejection vs. Frequency
PSRR vs. Frequency
10006061
10006051
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CMRR vs. Frequency
CMRR vs. Input Common Mode Voltage
10006064
10006062
CMRR vs. Input Common Mode Voltage
ΔVOS vs. CMR
10006063
10006053
Input Voltage vs. Output Voltage
ΔV OS vs. CMR
10006054
10006050
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Input Voltage vs. Output Voltage
Open Loop Frequency Response
10006052
10006042
Open Loop Frequency Response
Open Loop Frequency Response vs. Temperature
10006041
10006043
Gain and Phase vs. Capacitive Load
Gain and Phase vs. Capacitive Load
10006045
10006044
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Slew Rate vs. Supply Voltage
Non-Inverting Large Signal Pulse Response
10006088
10006057
Non-Inverting Large Signal Pulse Response
Non-Inverting Large Signal Pulse Response
100060a1
100060a0
Non-Inverting Small Signal Pulse Response
Non-Inverting Small Signal Pulse Response
10006089
100060a2
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Non-Inverting Small Signal Pulse Response
Inverting Large Signal Pulse Response
100060a3
10006090
Inverting Large Signal Pulse Response
Inverting Large Signal Pulse Response
100060a4
100060a5
Inverting Small Signal Pulse Response
Inverting Small Signal Pulse Response
10006091
100060a6
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Inverting Small Signal Pulse Response
Stability vs. Capacitive Load
Stability vs. Capacitive Load
THD vs. Frequency
100060a7
10006046
Stability vs. Capacitive Load
10006049
10006047
Stability vs. Capacitive Load
10006059
10006048
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Open Loop Output Impedance vs. Frequency
Short Circuit Current vs. Temperature (Sinking)
10006055
10006065
Short Circuit Current vs. Temperature (Sourcing)
10006066
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Application Information
BENEFITS OF THE LMV321/LMV358/LMV324
Size
The small footprints of the LMV321/LMV358/LMV324 pack-
ages 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/LMV358/LMV324 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/LMV358/LMV324 can be placed closer to the signal
source, reducing noise pickup and increasing signal integrity.
10006097
FIGURE 1. Output Swing of LMV324
Simplified Board Layout
These products help you to avoid using long PC traces in your
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
10006098
Rail-to-rail output swing provides maximum possible dynamic
range at the output. This is particularly important when oper-
ating on low supply voltages.
FIGURE 2. Output Swing of LM324
CAPACITIVE LOAD TOLERANCE
Input Includes Ground
The LMV321/LMV358/LMV324 can directly drive 200 pF in
unity-gain without oscillation. The unity-gain follower is the
most sensitive configuration to capacitive loading. Direct ca-
pacitive loading reduces the phase margin of amplifiers. The
combination of the amplifier's output impedance and the ca-
pacitive load induces phase lag. This results in either an
underdamped pulse response or oscillation. To drive a heav-
ier capacitive load, the circuit in Figure 3 can be used.
Allows direct sensing near GND in single supply operation.
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 and Crossover Distortion
The LMV321/LMV358/LMV324 offer specifications similar to
the familiar LM324. In addition, the new LMV321/LMV358/
LMV324 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 VS = ± 2.5V and RL (= 2 kΩ) connected to
GND. It is apparent that the crossover distortion has been
eliminated in the new LMV324.
10006004
FIGURE 3. Indirectly Driving a Capacitive Load Using
Resistive Isolation
13
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In Figure 3 , the isolation resistor RISO and the load capacitor
CL form a pole to increase stability by adding more phase
margin to the overall system. The desired performance de-
pends on the value of RISO. The bigger the RISO resistor value,
the more stable VOUT will be. Figure 4 is an output waveform
of Figure 3 using 620Ω for RISO and 510 pF for CL..
INPUT BIAS CURRENT CANCELLATION
The LMV321/LMV358/LMV324 family has a bipolar input
stage. The typical input bias current of LMV321/LMV358/
LMV324 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.
10006006
10006099
FIGURE 6. Cancelling the Error Caused by Input Bias
Current
FIGURE 4. Pulse Response of the LMV324 Circuit in
Figure 3
TYPICAL SINGLE-SUPPLY APPLICATION CIRCUITS
Difference Amplifier
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 RISO and the load resistor. Instead, in Fig-
ure 5, RF provides the DC accuracy by using feed-forward
techniques to connect VIN to RL. Caution is needed in choos-
ing the value of RF due to the input bias current of theLMV321/
LMV358/LMV324. CF and RISO 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, there-
by preserving phase margin in the overall feedback loop.
Increased capacitive drive is possible by increasing the value
of CF . This in turn will slow down the pulse response.
The difference amplifier allows the subtraction of two voltages
or, as a special case, the cancellation of a signal common to
two inputs. It is useful as a computational amplifier, in making
a differential to single-ended conversion or in rejecting a com-
mon mode signal.
10006007
10006005
10006019
FIGURE 5. Indirectly Driving A Capacitive Load with DC
Accuracy
FIGURE 7. Difference Amplifier
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Instrumentation Circuits
The input impedance of the previous difference amplifier is
set by the resistors R1, R2, R3, and R4. To eliminate the prob-
lems of low input impedance, one way is to use a voltage
follower ahead of each input as shown in the following two
instrumentation amplifiers.
Three-Op-Amp Instrumentation Amplifier
The quad LMV324 can be used to build a three-op-amp in-
strumentation amplifier as shown in Figure 8.
10006011
10006035
FIGURE 9. Two-Op-Amp Instrumentation Amplifier
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 R3 and R4 is
implemented to bias the amplifier so the input signal is within
the input common-mode voltage range of the amplifier. The
capacitor C1 is placed between the inverting input and resistor
R1 to block the DC signal going into the AC signal source,
VIN. The values of R1 and C1 affect the cutoff frequency, fc =
1/2πR1C1.
10006085
FIGURE 8. Three-Op-Amp Instrumentation Amplifier
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.
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 R2/R1. R3 should equal R1, and R4 equal
R2. Matching of R3 to R1 and R4 to R2 affects the CMRR. For
good CMRR over temperature, low drift resistors should be
used. Making R4 slightly smaller than R2 and adding a trim
pot equal to twice the difference between R2 and R4 will allow
the CMRR to be adjusted for optimum performance.
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 R1 and, R3 should equal R2.
10006013
10006020
FIGURE 10. Single-Supply Inverting Amplifier
15
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ACTIVE FILTER
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
Simple Low-Pass Active Filter
The simple low-pass filter is shown in Figure 11. Its low-fre-
quency gain (ω → 0) is defined by −R3/R1. This allows low-
frequency gains other than unity to be obtained. The filter has
a −20 dB/decade roll-off after its corner frequency fc. R2
should be chosen equal to the parallel combination of R1 and
R3 to minimize errors due to bias current. The frequency re-
sponse of the filter is shown in Figure 12.
(1)
Its transfer function is
(2)
10006014
10006016
FIGURE 13. Sallen-Key 2nd-Order Active Low-Pass Filter
The following paragraphs explain how to select values for
R1, R2, R3, R4, C1, and C 2 for given filter requirements, such
as ALP, Q, and fc.
10006037
The standard form for a 2nd-order low pass filter is
FIGURE 11. Simple Low-Pass Active Filter
(3)
where
Q: Pole Quality Factor
ꢁꢁωC: Corner Frequency
A comparison between Equation 2 and Equation 3 yields
10006015
(4)
(5)
FIGURE 12. Frequency Response of Simple Low-Pass
Active Filter in Figure 11
Note that the single-op-amp active filters are used in the ap-
plications that require low quality factor, Q( ≤ 10), low fre-
quency (≤ 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 fre-
quency. In addition, the selected op amp should have a slew
rate that meets the following requirement:
To reduce the required calculations in filter design, it is con-
venient to introduce normalization into the components and
design parameters. To normalize, let ωC = ωn = 1 rad/s, and
C1 = C2 = Cn = 1F, and substitute these values into Equation
4 and Equation 5. From Equation 4, we obtain
(6)
From Equation 5, we obtain
Slew Rate ≥ 0.5 × (ω HVOPP) × 10−6 V/µsec
where ωH is the highest frequency of interest, and VOPP is the
output peak-to-peak voltage.
(7)
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For minimum DC offset, V+ = V−, the resistor values at both
inverting and non-inverting inputs should be equal, which
means
Scaled values:
R2 = R1 = 15.9 kΩ
R3 = R4 = 63.6 kΩ
C1 = C2 = 0.01 µF
(8)
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.
From Equation 1 and Equation 8, we obtain
(9)
2nd-Order High Pass Filter
A 2nd-order high pass filter can be built by simply interchang-
ing those frequency selective components (R1, R2, C1, C2) in
the Sallen-Key 2nd-order active low pass filter. As shown in
Figure 14, resistors become capacitors, and capacitors be-
come resistors. The resulted high pass filter has the same
corner frequency and the same maximum gain as the previ-
ous 2nd-order low pass filter if the same components are
chosen.
(10)
The values of C1 and C2 are normally close to or equal to
As a design example:
Require: ALP = 2, Q = 1, fc = 1 kHz
Start by selecting C1 and C2. Choose a standard value that is
close to
From Equations 6, 7, 9, 10,
R1= 1Ω
R2= 1Ω
R3= 4Ω
R4= 4Ω
The above resistor values are normalized values with ωn = 1
rad/s and C1 = C2 = Cn = 1F. To scale the normalized cutoff
frequency and resistances to the real values, two scaling fac-
tors are introduced, frequency scaling factor (kf) and
impedance scaling factor (km).
10006083
FIGURE 14. Sallen-Key 2nd-Order Active High-Pass Filter
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 three different outputs.
The equations for these functions are listed below. It is also
called "Bi-Quad" active filter as it can produce a transfer func-
tion which is quadratic in both numerator and denominator.
17
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10006039
FIGURE 15. State Variable Active Filter
From Equation 12,
From the above calculated values, the midband gain is
H0 = R3/R2 = 100 (40 dB). The nearest 5% standard values
have been added to Figure 15.
PULSE GENERATORS AND OSCILLATORS
A pulse generator is shown in Figure 16. Two diodes have
been used to separate the charge and discharge paths to ca-
pacitor C.
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 to be calculated are capacitor
and resistor values.
First choose convenient values for C1, R1 and R2:
C1 = 1200 pF
2R2 = R1 = 30 kΩ
Then from Equation 11,
10006081
FIGURE 16. Pulse Generator
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When the output voltage VO is first at its high, VOH, the ca-
pacitor C is charged toward VOH through R2. The voltage
across C rises exponentially with a time constant τ = R2C, 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 (VTH+) of the generator. The ca-
pacitor voltage continually increases until it reaches VTH+, at
which point the output of the generator will switch to its low,
VOL which 0V is in this case. The voltage at the non-inverting
input is switched to the negative threshold voltage (VTH−) of
the generator. The capacitor then starts to discharge toward
VOL exponentially through R1, with a time constant τ = R1C.
When the capacitor voltage reaches VTH−, the output of the
pulse generator switches to VOH. The capacitor starts to
charge, and the cycle repeats itself.
10006077
FIGURE 18. Pulse Generator
Figure 19 is a squarewave generator with the same path for
charging and discharging the capacitor.
10006076
FIGURE 19. Squarewave Generator
CURRENT SOURCE AND SINK
10006086
The LMV321/LMV358/LMV324 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.
FIGURE 17. Waveforms of the Circuit in Figure 16
As shown in the waveforms in Figure 17, the pulse width
(T1) is set by R2, C and VOH, and the time between pulses
(T2) is set by R1, C and VOL. This pulse generator can be made
to have different frequencies and pulse width by selecting dif-
ferent capacitor value and resistor values.
Fixed Current Source
A multiple fixed current source is shown in Figure 20. A volt-
age (VREF = 2V) is established across resistor R3 by the
voltage divider (R3 and R4). Negative feedback is used to
cause the voltage drop across R1 to be equal to VREF. This
controls the emitter current of transistor Q1 and if we neglect
the base current of Q1 and Q2, essentially this same current
is available out of the collector of Q1.
Figure 18 shows another pulse generator, with separate
charge and discharge paths. The capacitor is charged
through R1 and is discharged through R2.
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 Q1.
The resistor, R2, can be used to scale the collector current of
Q2 either above or below the 1 mA reference value.
19
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LED DRIVER
The LMV321/LMV358/LMV324 can be used to drive an LED
as shown in Figure 23.
10006084
FIGURE 23. LED Driver
COMPARATOR WITH HYSTERESIS
The LMV321/LMV358/LMV324 can be used as a low power
comparator. Figure 24 shows a comparator with hysteresis.
The hysteresis is determined by the ratio of the two resistors.
10006080
FIGURE 20. Fixed Current Source
High Compliance Current Sink
VTH+ = VREF/(1+R 1/R2)+VOH/(1+R2/R1)
VTH− = VREF/(1+R 1/R2)+VOL/(1+R2/R1)
VH = (VOH−VOL)/(1+R 2/R1)
A current sink circuit is shown in Figure 21. The circuit re-
quires only one resistor (RE) and supplies an output current
which is directly proportional to this resistor value.
where
VTH+: Positive Threshold Voltage
VTH−: Negative Threshold Voltage
VOH: Output Voltage at High
VOL: Output Voltage at Low
VH: Hysteresis Voltage
Since LMV321/LMV358/LMV324 have rail-to-rail output, the
(VOH−VOL) is equal to VS, which is the supply voltage.
VH = VS/(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 use
National's LMV331/LMV93/LMV339, which are single, dual
and quad general purpose comparators for low voltage oper-
ation.
10006082
FIGURE 21. High Compliance Current Sink
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.
10006078
FIGURE 24. Comparator with Hysteresis
10006079
FIGURE 22. Power Amplifier
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20
SC70-5 Tape and Reel Specification
100060b3
SOT-23-5 Tape and Reel Specification
TAPE FORMAT
Tape Section
Leader
# Cavities
0 (min)
75 (min)
3000
Cavity Status
Empty
Cover Tape Status
Sealed
(Start End)
Carrier
Empty
Sealed
Filled
Sealed
250
Filled
Sealed
Trailer
125 (min)
0 (min)
Empty
Sealed
(Hub End)
Empty
Sealed
21
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TAPE DIMENSIONS
100060b1
8 mm
0.130
0.124
(3.15)
0.130
(3.3)
0.126
(3.2)
0.138 ±0.002
(3.5 ±0.05)
DIM F
0.055 ±0.004
(1.4 ±0.11)
DIM Ko
0.157
(4)
0.315 ±0.012
(8 ±0.3)
(3.3)
Tape Size
DIM A
DIM Ao
DIM B
DIM Bo
DIM P1
DIM W
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22
REEL DIMENSIONS
100060b2
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
W1 + 2.00/−1.00
W3
330.00 1.50 13.00 20.20 55.00
8.40 + 1.50/−0.00
14.40
Tape Size
A
B
C
D
N
W1
W2
23
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Physical Dimensions inches (millimeters) unless otherwise noted
5-Pin SC70
NS Package Number MAA05A
5-Pin SOT23
NS Package Number MF05A
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24
8-Pin SOIC
NS Package Number M08A
8-Pin MSOP
NS Package Number MUA08A
25
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14-Pin SOIC
NS Package Number M14A
14-Pin TSSOP
NS Package Number MTC14
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26
Notes
27
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Notes
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相关型号：
LMV358A-Q1
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