LMV321/LMV358/LMV324 Single/Dual/Quad General Purpose, Low Voltage, Rail-to-Rail Output Operational Amplifiers
Literature Number: SNOS012F
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LMV321/LMV358/LMV324 Single/Dual/Quad General Purpose, Low Voltage, Rail-to-Rail OutputOperational AmplifiersLMV321/LMV358/LMV324
Single/Dual/Quad
September 22, 2009
General Purpose, Low Voltage, Rail-to-Rail OutputOperational Amplifiers
General Description
The LMV358/LMV324 are low voltage (2.7–5.5V) versions ofthe dual and quad commodity op amps, LM358/LMV324,which currently operate at 5–30V. The LMV321 is the singleversion.
The LMV321/LMV358/LMV324 are the most cost effectivesolutions 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. TheLMV321/LMV358/LMV324 have rail-to-rail output swing ca-pability and the input common-mode voltage range includesground. They all exhibit excellent speed to power ratio,achieving 1 MHz of bandwidth and 1 V/µs of slew rate withlow supply current.
The LMV321 is available in the space saving 5-Pin SC70,which is approximately half the size of the 5-Pin SOT23. Thesmall package saves space on PC boards, and enables thedesign of small portable electronic devices. It also allows thedesigner to place the device closer to the signal source toreduce noise pickup and increase signal integrity.
The chips are built with National's advanced submicron sili-con-gate BiCMOS process. The LMV321/LMV358/LMV324have bipolar input and output stages for improved noise per-formance and higher output current drive.
Gain and Phase vs. Capacitive Load
Features
(For V+ = 5V and V− = 0V, unless otherwise specified)■Guaranteed 2.7V and 5V performance■No crossover distortion
−40°C to +85°C■Industrial temperature range
1 MHz■Gain-bandwidth product
■Low supply current—LMV321130 μA—LMV358210 μA—LMV324410 μA
+V −10 mV■Rail-to-rail output swing @ 10 kΩ
V− +65 mV−0.2V to V+−0.8V■VCM
Applications
■Active filters
■General purpose low voltage applications■General purpose portable devices
Output Voltage Swing vs. Supply Voltage
1000604510006067
© 2009 National Semiconductor Corporation100060www.national.com
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LMV321/LMV358/LMV324 Single/Dual/QuadAbsolute 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) Human Body Model LMV358/LMV324 LMV321
Machine Model
Differential Input VoltageInput Voltage
Supply Voltage (V+–V −)Output Short Circuit to V +Output Short Circuit to V −Soldering Information
2000V900V100V
±Supply Voltage
−0.3V to +Supply Voltage
5.5V(Note 3)(Note 4)
Infrared or Convection (30 sec)
Storage Temp. Range
Junction Temperature (Note 5)
260°C
−65°C to 150°C
150°C
(Note 1)
2.7V to 5.5V−40°C to +85°C
478°C/W265°C/W190°C/W235°C/W145°C/W155°C/W
Operating Ratings
Supply Voltage
Temperature Range (Note 5) LMV321/LMV358/LMV324
Thermal Resistance (θ JA) (Note 10) 5-pin SC70 5-pin SOT23 8-Pin SOIC 8-Pin MSOP 14-Pin SOIC 14-Pin TSSOP
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.SymbolVOSTCVOSIBIOSCMRRPSRRVCMVOIS
Parameter
Input Offset Voltage
Input Offset Voltage Average DriftInput Bias CurrentInput Offset Current
Common Mode Rejection RatioPower Supply Rejection Ratio
0V ≤ VCM ≤ 1.7V2.7V ≤ V+ ≤ 5VVO = 1V
Conditions
Min(Note 7)
50500
Output SwingSupply Current
RL = 10 kΩ to 1.35VLMV321LMV358
Both amplifiersLMV324
All four amplifiers
V+ −100
Typ(Note 6)1.751156360−0.21.9V+ −106080140260
Max(Note 7)
7 25050 1.7 180170340680
UnitsmVµV/°CnAnAdBdBVVmVmVµAµAµA
Input Common-Mode Voltage RangeFor CMRR ≥ 50 dB
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.SymbolGBWPΦmGmenin
Parameter
Gain-Bandwidth ProductPhase MarginGain Margin
Input-Referred Voltage NoiseInput-Referred Current Noise
Conditions
CL = 200 pF f = 1 kHzf = 1 kHz
Min(Note 7)
Typ(Note 6)
16010460.17
Max(Note 7)
UnitsMHzDegdB
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LMV321/LMV358/LMV324 Single/Dual/Quad5V 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.SymbolVOSTCVOSIBIOSCMRRPSRRVCMAVVO
Parameter
Input Offset Voltage
Input Offset Voltage Average DriftInput Bias CurrentInput Offset Current
Common Mode Rejection RatioPower Supply Rejection RatioInput Common-Mode VoltageRange
Large Signal Voltage Gain(Note 8)Output Swing
0V ≤ VCM ≤ 4V2.7V ≤ V+ ≤ 5VVO = 1V, VCM = 1VFor CMRR ≥ 50 dBRL = 2 kΩRL = 2 kΩ to 2.5V
Conditions
Min(Note 7)
50500 1510V+ −300V+ −400
RL = 10 kΩ to 2.5V
V+ −100V+ −200
IOIS
Output Short Circuit CurrentSupply Current
Sourcing, VO = 0VSinking, VO = 5VLMV321LMV358
Both amplifiersLMV324
All four amplifiers
510
Typ(Note 6)1.751556560−0.24.2100V+ −40120V+ −106560160130210410
Max(Note 7)
79 25050050150 4 300400 180280 2503504406158301160
Units
mVµV/°CnAnAdBdBVVV/mVmVmVmVmVmAµAµAµA
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.SymbolSRGBWPΦmGmenin
Slew Rate
Gain-Bandwidth ProductPhase MarginGain Margin
Input-Referred Voltage NoiseInput-Referred Current Noise
Parameter
(Note 9)CL = 200 pF f = 1 kHzf = 1 kHz
Conditions
Min(Note 7)
Typ(Note 6)
116010390.21
Max(Note 7)
UnitsV/µsMHzDegdB
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LMV321/LMV358/LMV324 Single/Dual/QuadNote 1:Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device isintended 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 JEDECNote 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 temperatureis 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 willalso 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
Top View
10006001
Top View
10006002
Top View
10006003
Ordering Information
Temperature Range
Package
Industrial−40°C to +85°CLMV321M7LMV321M7XLMV321M5LMV321M5XLMV358MLMV358MXLMV358MMLMV358MMXLMV324MLMV324MXLMV324MTLMV324MTX
Packaging Marking
Transport Media1k Units Tape and Reel3k Units Tape and Reel1k Units Tape and Reel3k Units Tape and Reel
Rails
2.5k Units Tape and Reel1k Units Tape and Reel3.5k Units Tape and Reel
Rails
2.5k Units Tape and Reel
Rails
2.5k Units Tape and Reel
NSC Drawing
5-Pin SC705-Pin SOT238-Pin SOIC8-Pin MSOP14-Pin SOIC14-Pin TSSOP
A12A13LMV358MLMV358LMV324MLMV324MT
MAA05AMF05AM08AMUA08AM14AMTC14
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LMV321/LMV358/LMV324 Single/Dual/QuadTypical Performance Characteristics
TA = 25°C.
Supply Current vs. Supply Voltage (LMV321)
Unless otherwise specified, VS = +5V, single supply,
Input Current vs. Temperature
10006073100060a9
Sourcing Current vs. Output VoltageSourcing Current vs. Output Voltage
1000606910006068
Sinking Current vs. Output VoltageSinking Current vs. Output Voltage
1000607010006071
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LMV321/LMV358/LMV324 Single/Dual/QuadOutput Voltage Swing vs. Supply VoltageInput Voltage Noise vs. Frequency
1000606710006056
Input Current Noise vs. FrequencyInput Current Noise vs. Frequency
1000606010006058
Crosstalk Rejection vs. FrequencyPSRR vs. Frequency
1000606110006051
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LMV321/LMV358/LMV324 Single/Dual/QuadCMRR vs. FrequencyCMRR vs. Input Common Mode Voltage
10006062
10006064
CMRR vs. Input Common Mode Voltage
ΔVOS vs. CMR
10006063
10006053
ΔV OS vs. CMR
Input Voltage vs. Output Voltage
10006050
10006054
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LMV321/LMV358/LMV324 Single/Dual/QuadInput Voltage vs. Output VoltageOpen Loop Frequency Response
10006052
10006042
Open Loop Frequency ResponseOpen Loop Frequency Response vs. Temperature
1000604110006043
Gain and Phase vs. Capacitive LoadGain and Phase vs. Capacitive Load
1000604510006044
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LMV321/LMV358/LMV324 Single/Dual/QuadSlew Rate vs. Supply VoltageNon-Inverting Large Signal Pulse Response
10006057
10006088
Non-Inverting Large Signal Pulse ResponseNon-Inverting Large Signal Pulse Response
100060a1100060a0
Non-Inverting Small Signal Pulse ResponseNon-Inverting Small Signal Pulse Response
10006089100060a2
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LMV321/LMV358/LMV324 Single/Dual/QuadNon-Inverting Small Signal Pulse ResponseInverting Large Signal Pulse Response
100060a310006090
Inverting Large Signal Pulse ResponseInverting Large Signal Pulse Response
100060a4100060a5
Inverting Small Signal Pulse ResponseInverting Small Signal Pulse Response
10006091100060a6
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LMV321/LMV358/LMV324 Single/Dual/QuadInverting Small Signal Pulse ResponseStability vs. Capacitive Load
100060a7
10006046
Stability vs. Capacitive LoadStability vs. Capacitive Load
1000604710006049
Stability vs. Capacitive LoadTHD vs. Frequency
10006048
10006059
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LMV321/LMV358/LMV324 Single/Dual/QuadOpen Loop Output Impedance vs. FrequencyShort Circuit Current vs. Temperature (Sinking)
10006055
10006065
Short Circuit Current vs. Temperature (Sourcing)
10006066
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LMV321/LMV358/LMV324 Single/Dual/QuadApplication 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 thedesign of smaller electronic products, such as cellularphones, pagers, or other portable systems. The low profile ofthe LMV321/LMV358/LMV324 make them possible to use inPCMCIA type III cards.
Signal Integrity
Signals can pick up noise between the signal source and theamplifier. By using a physically smaller amplifier package, theLMV321/LMV358/LMV324 can be placed closer to the signalsource, reducing noise pickup and increasing signal integrity.Simplified Board Layout
These products help you to avoid using long PC traces in yourPC board layout. This means that no additional components,such as capacitors and resistors, are needed to filter out theunwanted signals due to the interference between the longPC traces.
Low Supply Current
These devices will help you to maximize battery life. They areideal for battery powered systems.
Low Supply Voltage
National provides guaranteed performance at 2.7V and 5V.These guarantees ensure operation throughout the batterylifetime.
Rail-to-Rail Output
Rail-to-rail output swing provides maximum possible dynamicrange at the output. This is particularly important when oper-ating on low supply voltages.
Input Includes Ground
Allows direct sensing near GND in single supply operation.Protection should be provided to prevent the input voltagesfrom going negative more than −0.3V (at 25°C). An inputclamp diode with a resistor to the IC input terminal can beused.
Ease of Use and Crossover Distortion
The LMV321/LMV358/LMV324 offer specifications similar tothe 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 outputswing of the LMV324 and the LM324 in a voltage followerconfiguration, with VS = ± 2.5V and RL (= 2 kΩ) connected toGND. It is apparent that the crossover distortion has beeneliminated in the new LMV324.
10006098
10006097
FIGURE 1. Output Swing of LMV324
FIGURE 2. Output Swing of LM324
CAPACITIVE LOAD TOLERANCE
The LMV321/LMV358/LMV324 can directly drive 200 pF inunity-gain without oscillation. The unity-gain follower is themost sensitive configuration to capacitive loading. Direct ca-pacitive loading reduces the phase margin of amplifiers. Thecombination of the amplifier's output impedance and the ca-pacitive load induces phase lag. This results in either anunderdamped pulse response or oscillation. To drive a heav-ier capacitive load, the circuit in Figure 3 can be used.
10006004
FIGURE 3. Indirectly Driving a Capacitive Load Using
Resistive Isolation
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LMV321/LMV358/LMV324 Single/Dual/QuadIn Figure 3 , the isolation resistor RISO and the load capacitorCL form a pole to increase stability by adding more phasemargin 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 waveformof Figure 3 using 620Ω for RISO and 510 pF for CL..
INPUT BIAS CURRENT CANCELLATION
The LMV321/LMV358/LMV324 family has a bipolar inputstage. The typical input bias current of LMV321/LMV358/LMV324 is 15 nA with 5V supply. Thus a 100 kΩ input resistorwill cause 1.5 mV of error voltage. By balancing the resistorvalues at both inverting and non-inverting inputs, the errorcaused by the amplifier's input bias current will be reduced.The circuit in Figure 6 shows how to cancel the error causedby input bias current.
10006006
10006099
FIGURE 4. Pulse Response of the LMV324 Circuit in
Figure 3The circuit in Figure 5 is an improvement to the one in Figure3 because it provides DC accuracy as well as AC stability. Ifthere were a load resistor in Figure 3, the output would bevoltage divided by RISO and the load resistor. Instead, in Fig-ure 5, RF provides the DC accuracy by using feed-forwardtechniques 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 lossof phase margin by feeding the high frequency component ofthe 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 valueof CF . This in turn will slow down the pulse response.
FIGURE 6. Cancelling the Error Caused by Input Bias
CurrentTYPICAL SINGLE-SUPPLY APPLICATION CIRCUITSDifference Amplifier
The difference amplifier allows the subtraction of two voltagesor, as a special case, the cancellation of a signal common totwo inputs. It is useful as a computational amplifier, in makinga differential to single-ended conversion or in rejecting a com-mon mode signal.
10006007
10006005
FIGURE 5. Indirectly Driving A Capacitive Load with DC
Accuracy
10006019
FIGURE 7. Difference Amplifier
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LMV321/LMV358/LMV324 Single/Dual/QuadInstrumentation Circuits
The input impedance of the previous difference amplifier isset by the resistors R1, R2, R3, and R4. To eliminate the prob-lems of low input impedance, one way is to use a voltagefollower ahead of each input as shown in the following twoinstrumentation 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 AmplifierSingle-Supply Inverting Amplifier
There may be cases where the input signal going into theamplifier is negative. Because the amplifier is operating insingle supply voltage, a voltage divider using R3 and R4 isimplemented to bias the amplifier so the input signal is withinthe input common-mode voltage range of the amplifier. Thecapacitor C1 is placed between the inverting input and resistorR1 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.
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.
10006085
FIGURE 8. Three-Op-Amp Instrumentation AmplifierThe 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 impedanceis over 100 MΩ. The gain of this instrumentation amplifier isset by the ratio of R2/R1. R3 should equal R1, and R4 equalR2. Matching of R3 to R1 and R4 to R2 affects the CMRR. Forgood CMRR over temperature, low drift resistors should beused. Making R4 slightly smaller than R2 and adding a trimpot equal to twice the difference between R2 and R4 will allowthe CMRR to be adjusted for optimum performance.Two-Op-Amp Instrumentation Amplifier
A two-op-amp instrumentation amplifier can also be used tomake a high-input-impedance DC differential amplifier (Fig-ure 9). As in the three-op-amp circuit, this instrumentationamplifier requires precise resistor matching for good CMRR.R4 should equal R1 and, R3 should equal R2.
10006013
10006020
FIGURE 10. Single-Supply Inverting Amplifier
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LMV321/LMV358/LMV324 Single/Dual/QuadACTIVE FILTER
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 hasa −20 dB/decade roll-off after its corner frequency fc. R2should be chosen equal to the parallel combination of R1 andR3 to minimize errors due to bias current. The frequency re-sponse of the filter is shown in Figure 12.
Sallen-Key 2nd-Order Active Low-Pass Filter
The Sallen-Key 2nd-order active low-pass filter is illustratedin Figure 13. The DC gain of the filter is expressed as
(1)
Its transfer function is
(2)
10006014
10006016
FIGURE 13. Sallen-Key 2nd-Order Active Low-Pass FilterThe following paragraphs explain how to select values forR1, R2, R3, R4, C1, and C 2 for given filter requirements, suchas ALP, Q, and fc.
The standard form for a 2nd-order low pass filter is
10006037
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
(4)
10006015
FIGURE 12. Frequency Response of Simple Low-Pass
Active Filter in Figure 11Note 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 forthe product of gain times Q (≤ 100). The op amp should havean open loop voltage gain at the highest frequency of interestat least 50 times larger than the gain of the filter at this fre-quency. In addition, the selected op amp should have a slewrate that meets the following requirement:
Slew Rate ≥ 0.5 × (ω HVOPP) × 10−6 V/µsec
where ωH is the highest frequency of interest, and VOPP is theoutput peak-to-peak voltage.
(5)
To reduce the required calculations in filter design, it is con-venient to introduce normalization into the components anddesign parameters. To normalize, let ωC = ωn = 1 rad/s, andC1 = C2 = Cn = 1F, and substitute these values into Equation4 and Equation 5. From Equation 4, we obtain
(6)
From Equation 5, we obtain
(7)
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LMV321/LMV358/LMV324 Single/Dual/QuadFor minimum DC offset, V+ = V−, the resistor values at bothinverting and non-inverting inputs should be equal, whichmeans
Scaled values:
R2 = R1 = 15.9 kΩR3 = R4 = 63.6 kΩC1 = C2 = 0.01 µF
An adjustment to the scaling may be made in order to haverealistic values for resistors and capacitors. The actual valueused for each component is shown in the circuit.
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) inthe Sallen-Key 2nd-order active low pass filter. As shown inFigure 14, resistors become capacitors, and capacitors be-come resistors. The resulted high pass filter has the samecorner frequency and the same maximum gain as the previ-ous 2nd-order low pass filter if the same components arechosen.
(8)
From Equation 1 and Equation 8, we obtain
(9)
(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 isclose to
From Equations 6, 7, 9, 10,
R1= 1ΩR2= 1ΩR3= 4ΩR4= 4Ω
The above resistor values are normalized values with ωn = 1rad/s and C1 = C2 = Cn = 1F. To scale the normalized cutofffrequency and resistances to the real values, two scaling fac-tors are introduced, frequency scaling factor (kf) andimpedance scaling factor (km).
10006083
FIGURE 14. Sallen-Key 2nd-Order Active High-Pass FilterState Variable Filter
A state variable filter requires three op amps. One convenientway to build state variable filters is with a quad op amp, suchas 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 alsocalled \"Bi-Quad\" active filter as it can produce a transfer func-tion which is quadratic in both numerator and denominator.
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LMV321/LMV358/LMV324 Single/Dual/Quad10006039
FIGURE 15. State Variable Active Filter
From Equation 12,
From the above calculated values, the midband gain isH0 = R3/R2 = 100 (40 dB). The nearest 5% standard valueshave been added to Figure 15.
PULSE GENERATORS AND OSCILLATORS
A pulse generator is shown in Figure 16. Two diodes havebeen 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 capacitorand resistor values.
First choose convenient values for C1, R1 and R2:
C1 = 1200 pF2R2 = R1 = 30 kΩ
Then from Equation 11,
10006081
FIGURE 16. Pulse Generator
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LMV321/LMV358/LMV324 Single/Dual/QuadWhen the output voltage VO is first at its high, VOH, the ca-pacitor C is charged toward VOH through R2. The voltageacross C rises exponentially with a time constant τ = R2C, andthis voltage is applied to the inverting input of the op amp.Meanwhile, the voltage at the non-inverting input is set at thepositive threshold voltage (VTH+) of the generator. The ca-pacitor voltage continually increases until it reaches VTH+, atwhich point the output of the generator will switch to its low,VOL which 0V is in this case. The voltage at the non-invertinginput is switched to the negative threshold voltage (VTH−) ofthe generator. The capacitor then starts to discharge towardVOL exponentially through R1, with a time constant τ = R1C.When the capacitor voltage reaches VTH−, the output of thepulse generator switches to VOH. The capacitor starts tocharge, and the cycle repeats itself.
10006077
FIGURE 18. Pulse Generator
Figure 19 is a squarewave generator with the same path forcharging and discharging the capacitor.
10006076
FIGURE 19. Squarewave Generator
CURRENT SOURCE AND SINK
The LMV321/LMV358/LMV324 can be used in feedbackloops which regulate the current in external PNP transistorsto provide current sources or in external NPN transistors toprovide current sinks.
Fixed Current Source
A multiple fixed current source is shown in Figure 20. A volt-age (VREF = 2V) is established across resistor R3 by thevoltage divider (R3 and R4). Negative feedback is used tocause the voltage drop across R1 to be equal to VREF. Thiscontrols the emitter current of transistor Q1 and if we neglectthe base current of Q1 and Q2, essentially this same currentis available out of the collector of Q1.
Large input resistors can be used to reduce current loss anda Darlington connection can be used to reduce errors due tothe β of Q1.
The resistor, R2, can be used to scale the collector current ofQ2 either above or below the 1 mA reference value.
10006086
FIGURE 17. Waveforms of the Circuit in Figure 16As 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 madeto have different frequencies and pulse width by selecting dif-ferent capacitor value and resistor values.
Figure 18 shows another pulse generator, with separatecharge and discharge paths. The capacitor is chargedthrough R1 and is discharged through R2.
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LMV321/LMV358/LMV324 Single/Dual/QuadLED DRIVER
The LMV321/LMV358/LMV324 can be used to drive an LEDas shown in Figure 23.
10006084
FIGURE 23. LED Driver
COMPARATOR WITH HYSTERESIS
The LMV321/LMV358/LMV324 can be used as a low powercomparator. Figure 24 shows a comparator with hysteresis.The hysteresis is determined by the ratio of the two resistors.
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)
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 notexceed the specified absolute maximum ratings. For realcomparators that are much faster, we recommend you useNational's LMV331/LMV93/LMV339, which are single, dualand quad general purpose comparators for low voltage oper-ation.
10006080
FIGURE 20. Fixed Current Source
High Compliance Current Sink
A current sink circuit is shown in Figure 21. The circuit re-quires only one resistor (RE) and supplies an output currentwhich is directly proportional to this resistor value.
10006082
FIGURE 21. High Compliance Current Sink
POWER AMPLIFIER
A power amplifier is illustrated in Figure 22. This circuit canprovide a higher output current because a transistor followeris added to the output of the op amp.
10006078
FIGURE 24. Comparator with Hysteresis
10006079
FIGURE 22. Power Amplifier
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LMV321/LMV358/LMV324 Single/Dual/QuadSC70-5 Tape and Reel Specification
100060b3
SOT-23-5 Tape and Reel Specification
TAPE FORMAT
Tape Section
Leader(Start End)Carrier Trailer(Hub End)
# Cavities0 (min)75 (min)3000250125 (min)0 (min)
Cavity Status
EmptyEmptyFilledFilledEmptyEmpty
Cover Tape Status
SealedSealedSealedSealedSealedSealed
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LMV321/LMV358/LMV324 Single/Dual/QuadTAPE DIMENSIONS
100060b1
8 mm Tape Size
0.130(3.3)DIM A
0.124(3.15)DIM Ao
0.130(3.3)DIM B
0.126(3.2)DIM Bo
0.138 ±0.002(3.5 ±0.05)
DIM F
0.055 ±0.004(1.4 ±0.11)DIM Ko
0.157(4)DIM P1
0.315 ±0.012(8 ±0.3)DIM W
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LMV321/LMV358/LMV324 Single/Dual/QuadREEL DIMENSIONS
100060b2
8 mm Tape Size
7.000.0590.5120.7952.165330.001.5013.0020.2055.00A
B
C
D
N
0.331 + 0.059/−0.0008.40 + 1.50/−0.00
W1
0.56714.40W2
W1+ 0.078/−0.039W1 + 2.00/−1.00
W3
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LMV321/LMV358/LMV324 Single/Dual/QuadPhysical Dimensions inches (millimeters) unless otherwise noted
5-Pin SC70
NS Package Number MAA05A
5-Pin SOT23
NS Package Number MF05A
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LMV321/LMV358/LMV324 Single/Dual/Quad8-Pin SOIC
NS Package Number M08A
8-Pin MSOP
NS Package Number MUA08A
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LMV321/LMV358/LMV324 Single/Dual/Quad14-Pin SOIC
NS Package Number M14A
14-Pin TSSOP
NS Package Number MTC14
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LMV321/LMV358/LMV324 Single/Dual/QuadNotes
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LMV321/LMV358/LMV324 Single/Dual/Quad General Purpose, Low Voltage, Rail-to-Rail OutputOperational AmplifiersNotes
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