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 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. 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 specifications that meet or exceed the familiar LM358/LMV324. The LMV321/LMV358/LMV324 have rail-to-rail output swing capability 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. 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. The chips are built with National's advanced submicron silicon-gate BiCMOS process. The LMV321/LMV358/LMV324 have bipolar input and output stages for improved noise performance and higher output current drive. (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 — LMV321 130 μA — LMV358 210 μA — LMV324 410 μA V+ −10 mV ■ Rail-to-rail output swing @ 10 kΩ V− +65 mV −0.2V to V+−0.8V ■ VCM Gain and Phase vs. Capacitive Load Output Voltage Swing vs. Supply Voltage 10006045 © 2009 National Semiconductor Corporation 100060 Applications ■ Active filters ■ General purpose low voltage applications ■ General purpose portable devices 10006067 www.national.com LMV321/LMV358/LMV324 Single/Dual/Quad General Purpose, Low Voltage, Rail-to-Rail Output Operational Amplifiers LMV321/LMV358/LMV324 Single/Dual/Quad LMV321/LMV358/LMV324 Single/Dual/Quad Absolute Maximum Ratings (Note 1) Infrared or Convection (30 sec) Storage Temp. Range Junction Temperature (Note 5) 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 Voltage Input Voltage Supply Voltage (V+–V −) Output Short Circuit to V + Output Short Circuit to V − Soldering Information 260°C −65°C to 150°C 150°C Operating Ratings (Note 1) Supply Voltage Temperature Range (Note 5) LMV321/LMV358/LMV324 2000V 900V 100V ±Supply Voltage −0.3V to +Supply Voltage 5.5V (Note 3) (Note 4) 2.7V to 5.5V −40°C to +85°C Thermal Resistance (θ JA) (Note 10) 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 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 (Note 7) Typ (Note 6) Max (Note 7) 1.7 7 Units VOS Input Offset Voltage TCVOS Input Offset Voltage Average Drift 5 IB Input Bias Current 11 250 nA IOS Input Offset Current 5 50 nA CMRR Common Mode Rejection Ratio 0V ≤ VCM ≤ 1.7V 50 63 dB PSRR Power Supply Rejection Ratio 2.7V ≤ VO = 1V 50 60 dB VCM Input Common-Mode Voltage Range For CMRR ≥ 50 dB 0 −0.2 V VO Output Swing V+ −100 V+ −10 V+ ≤ 5V 1.9 IS Supply Current RL = 10 kΩ to 1.35V mV µV/°C 1.7 V mV 60 180 mV LMV321 80 170 µA LMV358 Both amplifiers 140 340 LMV324 All four amplifiers 260 680 µA µA 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 Typ (Note 6) GBWP Gain-Bandwidth Product Φm Gm en Input-Referred Voltage Noise f = 1 kHz 46 in Input-Referred Current Noise f = 1 kHz 0.17 Max (Note 7) Units 1 MHz Phase Margin 60 Deg Gain Margin 10 dB www.national.com CL = 200 pF Min (Note 7) 2 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 (Note 7) Typ (Note 6) Max (Note 7) 1.7 7 9 Units VOS Input Offset Voltage TCVOS Input Offset Voltage Average Drift 5 IB Input Bias Current 15 250 500 nA IOS Input Offset Current 5 50 150 nA CMRR Common Mode Rejection Ratio 0V ≤ VCM ≤ 4V 50 65 dB PSRR Power Supply Rejection Ratio 2.7V ≤ V+ ≤ 5V VO = 1V, VCM = 1V 50 60 dB VCM Input Common-Mode Voltage Range For CMRR ≥ 50 dB 0 −0.2 AV Large Signal Voltage Gain (Note 8) RL = 2 kΩ VO Output Swing RL = 2 kΩ to 2.5V 4.2 15 10 100 V+ −300 V+ −400 V+ −40 120 RL = 10 kΩ to 2.5V V+ −100 V+ −200 Output Short Circuit Current IS Supply Current µV/°C V 4 V V/mV mV 300 400 mV V+ −10 65 IO mV Sourcing, VO = 0V 5 60 Sinking, VO = 5V 10 160 mV 180 280 mV mA LMV321 130 250 350 µA LMV358 Both amplifiers 210 440 615 µA LMV324 All four amplifiers 410 830 1160 µA 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 (Note 7) Typ (Note 6) Max (Note 7) Units SR Slew Rate (Note 9) 1 V/µs GBWP Gain-Bandwidth Product CL = 200 pF 1 MHz Φm Phase Margin 60 Deg Gm Gain Margin 10 dB en Input-Referred Voltage Noise f = 1 kHz 39 in Input-Referred Current Noise f = 1 kHz 0.21 3 www.national.com LMV321/LMV358/LMV324 Single/Dual/Quad 5V DC Electrical Characteristics LMV321/LMV358/LMV324 Single/Dual/Quad 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 5-Pin SC70 5-Pin SOT23 8-Pin SOIC 8-Pin MSOP 14-Pin SOIC 14-Pin TSSOP www.national.com Industrial −40°C to +85°C LMV321M7 LMV321M7X LMV321M5 LMV321M5X LMV358M LMV358MX LMV358MM LMV358MMX LMV324M LMV324MX LMV324MT LMV324MTX Packaging Marking A12 A13 LMV358M LMV358 LMV324M LMV324MT 4 Transport Media 1k Units Tape and Reel 3k Units Tape and Reel 1k Units Tape and Reel 3k Units Tape and Reel Rails 2.5k Units Tape and Reel 1k Units Tape and Reel 3.5k Units Tape and Reel Rails 2.5k Units Tape and Reel Rails 2.5k Units Tape and Reel NSC Drawing MAA05A MF05A M08A MUA08A M14A MTC14 Unless otherwise specified, VS = +5V, single supply, TA = 25°C. Supply Current vs. Supply Voltage (LMV321) Input Current vs. Temperature 100060a9 10006073 Sourcing Current vs. Output Voltage Sourcing Current vs. Output Voltage 10006069 10006068 Sinking Current vs. Output Voltage Sinking Current vs. Output Voltage 10006070 10006071 5 www.national.com LMV321/LMV358/LMV324 Single/Dual/Quad Typical Performance Characteristics LMV321/LMV358/LMV324 Single/Dual/Quad 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 10006051 10006061 www.national.com 6 CMRR vs. Input Common Mode Voltage 10006064 10006062 ΔVOS vs. CMR CMRR vs. Input Common Mode Voltage 10006063 10006053 ΔV OS vs. CMR Input Voltage vs. Output Voltage 10006054 10006050 7 www.national.com LMV321/LMV358/LMV324 Single/Dual/Quad CMRR vs. Frequency LMV321/LMV358/LMV324 Single/Dual/Quad 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 www.national.com 10006044 8 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 9 www.national.com LMV321/LMV358/LMV324 Single/Dual/Quad Slew Rate vs. Supply Voltage LMV321/LMV358/LMV324 Single/Dual/Quad 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 www.national.com 100060a6 10 Stability vs. Capacitive Load 100060a7 10006046 Stability vs. Capacitive Load Stability vs. Capacitive Load 10006049 10006047 Stability vs. Capacitive Load THD vs. Frequency 10006059 10006048 11 www.national.com LMV321/LMV358/LMV324 Single/Dual/Quad Inverting Small Signal Pulse Response LMV321/LMV358/LMV324 Single/Dual/Quad Open Loop Output Impedance vs. Frequency Short Circuit Current vs. Temperature (Sinking) 10006055 10006065 Short Circuit Current vs. Temperature (Sourcing) 10006066 www.national.com 12 BENEFITS OF THE LMV321/LMV358/LMV324 Size The small footprints of the LMV321/LMV358/LMV324 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/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 Rail-to-rail output swing provides maximum possible dynamic range at the output. This is particularly important when operating on low supply voltages. 10006098 FIGURE 2. Output Swing of LM324 CAPACITIVE LOAD TOLERANCE 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 capacitive loading reduces the phase margin of amplifiers. The combination of the amplifier's output impedance and the capacitive load induces phase lag. This results in either an underdamped pulse response or oscillation. To drive a heavier capacitive load, the circuit in Figure 3 can be used. Input Includes Ground 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 www.national.com LMV321/LMV358/LMV324 Single/Dual/Quad Application Information LMV321/LMV358/LMV324 Single/Dual/Quad 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 depends 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 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 Figure 5, RF provides the DC accuracy by using feed-forward techniques to connect VIN to RL. Caution is needed in choosing 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, thereby 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. Difference Amplifier 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 common mode signal. 10006007 10006005 10006019 FIGURE 5. Indirectly Driving A Capacitive Load with DC Accuracy www.national.com FIGURE 7. Difference Amplifier 14 Three-Op-Amp Instrumentation Amplifier The quad LMV324 can be used to build a three-op-amp instrumentation 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. 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-tonoise ratio in a low voltage system. 10006085 FIGURE 8. Three-Op-Amp Instrumentation Amplifier The first stage of this instrumentation amplifier is a differentialinput, 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 (Figure 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 www.national.com LMV321/LMV358/LMV324 Single/Dual/Quad Instrumentation Circuits The input impedance of the previous difference amplifier is set by the resistors R1, 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. LMV321/LMV358/LMV324 Single/Dual/Quad 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 ACTIVE FILTER Simple Low-Pass Active Filter The simple low-pass filter is shown in Figure 11. Its low-frequency gain (ω → 0) is defined by −R3/R1. This allows lowfrequency 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 response 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. 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 11 (5) Note that the single-op-amp active filters are used in 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: To reduce the required calculations in filter design, it is convenient 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) Slew Rate ≥ 0.5 × (ω HVOPP) × 10−6 V/µsec From Equation 5, we obtain where ωH is the highest frequency of interest, and VOPP is the output peak-to-peak voltage. www.national.com (7) 16 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 interchanging 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 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. (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 factors 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 function which is quadratic in both numerator and denominator. 17 www.national.com LMV321/LMV358/LMV324 Single/Dual/Quad For minimum DC offset, V+ = V−, the resistor values at both inverting and non-inverting inputs should be equal, which means LMV321/LMV358/LMV324 Single/Dual/Quad 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 capacitor 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 www.national.com 18 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 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. 10006086 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 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 R2. Fixed Current Source A multiple fixed current source is shown in Figure 20. A voltage (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. 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 www.national.com LMV321/LMV358/LMV324 Single/Dual/Quad When the output voltage VO is first at its high, VOH, the capacitor 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 capacitor 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. LMV321/LMV358/LMV324 Single/Dual/Quad 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 VTH+ = VREF/(1+R 1/R2)+VOH/(1+R2/R1) High Compliance Current Sink A current sink circuit is shown in Figure 21. The circuit requires only one resistor (RE) and supplies an output current which is directly proportional to this resistor value. 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 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 operation. 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 www.national.com 20 LMV321/LMV358/LMV324 Single/Dual/Quad SC70-5 Tape and Reel Specification 100060b3 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 21 www.national.com LMV321/LMV358/LMV324 Single/Dual/Quad TAPE DIMENSIONS 100060b1 8 mm 0.130 (3.3) 0.124 (3.15) 0.130 (3.3) 0.126 (3.2) 0.138 ±0.002 (3.5 ±0.05) 0.055 ±0.004 (1.4 ±0.11) 0.157 (4) 0.315 ±0.012 (8 ±0.3) Tape Size DIM A DIM Ao DIM B DIM Bo DIM F DIM Ko DIM P1 DIM W www.national.com 22 LMV321/LMV358/LMV324 Single/Dual/Quad REEL DIMENSIONS 100060b2 8 mm Tape Size 7.00 0.059 0.512 0.795 2.165 330.00 1.50 13.00 20.20 55.00 A B C D N 23 0.331 + 0.059/−0.000 8.40 + 1.50/−0.00 0.567 14.40 W1+ 0.078/−0.039 W1 + 2.00/−1.00 W1 W2 W3 www.national.com LMV321/LMV358/LMV324 Single/Dual/Quad Physical Dimensions inches (millimeters) unless otherwise noted 5-Pin SC70 NS Package Number MAA05A 5-Pin SOT23 NS Package Number MF05A www.national.com 24 LMV321/LMV358/LMV324 Single/Dual/Quad 8-Pin SOIC NS Package Number M08A 8-Pin MSOP NS Package Number MUA08A 25 www.national.com LMV321/LMV358/LMV324 Single/Dual/Quad 14-Pin SOIC NS Package Number M14A 14-Pin TSSOP NS Package Number MTC14 www.national.com 26 www.national.com 27 LMV321/LMV358/LMV324 Single/Dual/Quad Notes LMV321/LMV358/LMV324 Single/Dual/Quad General Purpose, Low Voltage, Rail-to-Rail Output Operational Amplifiers Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: Products Design Support Amplifiers www.national.com/amplifiers WEBENCH® Tools www.national.com/webench Audio www.national.com/audio App Notes www.national.com/appnotes Clock and Timing www.national.com/timing Reference Designs www.national.com/refdesigns Data Converters www.national.com/adc Samples www.national.com/samples Interface www.national.com/interface Eval Boards www.national.com/evalboards LVDS www.national.com/lvds Packaging www.national.com/packaging Power Management www.national.com/power Green Compliance www.national.com/quality/green Switching Regulators www.national.com/switchers Distributors www.national.com/contacts LDOs www.national.com/ldo Quality and Reliability www.national.com/quality LED Lighting www.national.com/led Feedback/Support www.national.com/feedback Voltage Reference www.national.com/vref Design Made Easy www.national.com/easy www.national.com/powerwise Solutions www.national.com/solutions Mil/Aero www.national.com/milaero PowerWise® Solutions Serial Digital Interface (SDI) www.national.com/sdi Temperature Sensors www.national.com/tempsensors SolarMagic™ www.national.com/solarmagic Wireless (PLL/VCO) www.national.com/wireless www.national.com/training PowerWise® Design University THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. 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