LMV358M/TR

LMV321/LMV358/LMV324 LMV321/LMV358/LMV324 Single/Dual/Quad General Purpose, Low Voltage, Rail-to-Rail Output Operational Amplifiers General Description Features 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. (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 V+ −10mV V− +65mV −0.2V to V+−0.8V n VCM 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 have rail-to-rail output swing capability and the input common-mode voltage range includes ground. They all exhibit excellent speed-power ratio, achieving 1MHz of bandwidth and 1V/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. Applications n ActiveFilters n GeneralPurposeLowVoltageApplications n GeneralPurposePortableDevices Output Voltage Swing vs. Supply Voltage Gain and Phase vs. Capacitive Load 10006045 http:www.hgsemi.com.cn 10006067 1 2018 AUG LMV321/LMV358/LMV324 Absolute Maximum Ratings Storage Temp. Range (Note 1) Supply Voltage 100V 2.7V to 5.5V Temperature Range Human Body Model LMV358/324 LMV321, LMV358, LMV324 2000V LMV321 Thermal Resistance (θ 900V ± Supply Voltage Differential Input Voltage + 150˚C Operating Ratings (Note 1) ESD Tolerance (Note 2) Machine Model −65˚C to 150˚C Junction Temperature(Note 5) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. − Supply Voltage (V –V ) 5.5V JA)(Note −40˚C to +85˚C 10) 5-pin SC70-5 478˚C/W 5-pin SOT23-5 265˚C/W 190˚C/W Output Short Circuit to V + (Note 3) 8-Pin SOIC Output Short Circuit to V − (Note 4) 8-Pin MSOP 235˚C/W 14-Pin SOIC 145˚C/W 14-Pin TSSOP 155˚C/W Soldering Information Infrared or Convection (20 sec) 235˚C 2.7V DC Electrical Characteristics Unless otherwise specified, all limits guaranteed for T Symbol Parameter J = 25˚C, V+ = 2.7V, V− = 0V, VCM = 1.0V, VO = V+/2 and RL > 1MΩ. Conditions Typ (Note 6) Limit (Note 7) 1.7 7 Units VOS Input Offset Voltage TCVOS Input Offset Voltage Average Drift 5 IB Input Bias Current 11 250 nA max IOS Input Offset Current 5 50 nA max CMRR Common Mode Rejection Ratio 0V ≤ VCM ≤ 1.7V 63 50 dB min PSRR Power Supply Rejection Ratio 2.7V ≤ V+ ≤ 5V VO = 1V 60 50 dB min VCM Input Common-Mode Voltage Range For CMRR≥50dB −0.2 0 V min 1.9 1.7 V max V+ -10 V+ -100 mV min 60 180 mV max LMV321 80 170 µA max LMV358 Both amplifiers 140 340 µA max LMV324 All four amplifiers 260 680 µA max VO IS Output Swing Supply Current http:www.hgsemi.com.cn RL = 10kΩ to 1.35V 2 mV max µV/˚C 2018 AUG LMV321/LMV358/LMV324 2.7V AC Electrical Characteristics Unless otherwise specified, all limits guaranteed for T Symbol Parameter J = 25˚C, V+ = 2.7V, V− = 0V, VCM = 1.0V, VO = V+/2 and RL > 1MΩ. Conditions CL = 200pF Typ (Note 6) Limit (Note 7) Units GBWP Gain-Bandwidth Product 1 MHz Φm Phase Margin 60 Deg Gm Gain Margin 10 dB en Input-Referred Voltage Noise f = 1kHz 46 in Input-Referred Current Noise f = 1kHz 0.17 5V DC Electrical Characteristics Unless otherwise specified, all limits guaranteed for T Boldface limits apply at the temperature extremes. Symbol Parameter J = 25˚C, V+ = 5V, V− = 0V, VCM = 2.0V, VO = V+/2 and R Conditions L > 1MΩ. Typ (Note 6) Limit (Note 7) 1.7 7 9 mV max µV/˚C 250 500 50 150 nA max nA max Units VOS Input Offset Voltage TCVOS Input Offset Voltage Average Drift Input Bias Current 15 IOS Input Offset Current 5 CMRR Common Mode Rejection Ratio 0V ≤ VCM ≤ 4V 65 50 dB min PSRR Power Supply Rejection Ratio 2.7V ≤ V+ ≤ 5V VO = 1V VCM = 1V 60 50 dB min Input Common-Mode Voltage For CMRR≥50dB −0.2 0 V min 4.2 4 100 15 V max V/mV min IB VCM AV 5 Range Large Signal Voltage Gain (Note RL = 2kΩ 8) Output Swing V+ -40 RL = 2kΩ to 2.5V VO 120 RL = 10kΩ to 2.5V IO Output Short Circuit Current Supply Current IS http:www.hgsemi.com.cn V+ -10 10 V+ -300 V+ -400 300 400 V+ -100 mV min mV max mV min 65 V+ -200 180 280 Sourcing, VO = 0V 60 5 Sinking, VO = 5V 160 10 LMV321 130 LMV358 Both amplifiers 210 250 350 440 615 µA max µA max LMV324 All four amplifiers 3 410 830 1160 µA max 3 mV max m min mA min 2018 AUG LMV321/LMV358/LMV324 5V AC Electrical Characteristics Unless otherwise specified, all limits guaranteed for T Boldface limits apply at the temperature extremes. Symbol Parameter J = 25˚C, V+ = 5V, V− = 0V, VCM = 2.0V, VO = V+/2 and R Conditions Typ (Note 6) Limit (Note 7) L > 1MΩ. Units SR Slew Rate (Note 9) 1 V/µs GBWP Gain-Bandwidth Product CL = 200pF 1 MHz Φm Phase Margin 60 Deg Gm Gain Margin 10 dB en Input-Referred Voltage Noise f = 1kHz 39 in Input-Referred Current Noise f = 1kHz 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, 1.5kΩ in series with 100pF. Machine model, 0Ω in series with 200pF. 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, and TA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(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: 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. http:www.hgsemi.com.cn 4 2018 AUG LMV321/LMV358/LMV324 Typical Performance Characteristics 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 http:www.hgsemi.com.cn 10006071 5 2018 AUG LMV321/LMV358/LMV324 Typical Performance Characteristics Unless otherwise specified, VS = +5V, single supply, TA = 25˚C. (Continued) 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 http:www.hgsemi.com.cn 6 2018 AUG LMV321/LMV358/LMV324 Typical Performance Characteristics Unless otherwise specified, VS = +5V, single supply, TA = 25˚C. (Continued) CMRR vs. Frequency CMRR vs. Input Common Mode Voltage 10006064 10006062 ∆VOS vs. CMR CMRR vs. Input Common Mode Voltage 10006063 ∆V OS 10006053 vs. CMR Input Voltage vs. Output Voltage 10006054 10006050 http:www.hgsemi.com.cn 7 2018 AUG LMV321/LMV358/LMV324 Typical Performance Characteristics Unless otherwise specified, VS = +5V, single supply, TA = 25˚C. (Continued) 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 http:www.hgsemi.com.cn 10006044 8 2018 AUG LMV321/LMV358/LMV324 Typical Performance Characteristics Unless otherwise specified, VS = +5V, single supply, TA = 25˚C. (Continued) 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 http:www.hgsemi.com.cn 100060A2 9 2018 AUG LMV321/LMV358/LMV324 Typical Performance Characteristics Unless otherwise specified, VS = +5V, single supply, TA = 25˚C. (Continued) 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 http:www.hgsemi.com.cn 100060A6 10 2018 AUG LMV321/LMV358/LMV324 Typical Performance Characteristics Unless otherwise specified, VS = +5V, single supply, TA = 25˚C. (Continued) Inverting Small Signal Pulse Response 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 http:www.hgsemi.com.cn 1 2018 AUG LMV321/LMV358/LMV324 Typical Performance Characteristics Unless otherwise specified, VS = +5V, single supply, TA = 25˚C. (Continued) Open Loop Output Impedance vs. Frequency Short Circuit Current vs. Temperature (Sinking) 10006055 10006065 Short Circuit Current vs. Temperature (Sourcing) 10006066 http:www.hgsemi.com.cn 12 2018 AUG LMV321/LMV358/LMV324 Application Notes Output Voltage (500mV/div) 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. Time (50µs/div) 10006097 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. Output Voltage (500mV/div) FIGURE 1. Output Swing of LMV324 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. Time (50µs/div) 10006098 FIGURE 2. Output Swing of LM324 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. 2.0 CAPACITIVE LOAD TOLERANCE The LMV321/358/324 can directly drive 200pF 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, circuit in Figure 3 can be used. Ease Of Use & 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. 10006004 FIGURE 3. Indirectly Driving A Capacitive Load Using Resistive Isolation http:www.hgsemi.com.cn 13 2018 AUG LMV321/LMV358/LMV324 Application Notes input bias current will be reduced. The circuit in Figure 6 shows how to cancel the error caused by input bias current. (Continued) (1v/div) Input Signal 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 510pF for CL.. 10006006 Output Signal FIGURE 6. Cancelling 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 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. Time (2µs/div) 10006099 FIGURE 4. Pulse Response of the LMV324 Circuit in Figure 3 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 feedforward techniques to connect VIN to RL. Caution is needed in choosing the value of RF due to the input bias current of the LMV321/358/324. 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 C F . This in turn will slow down the pulse response. 10006007 10006019 FIGURE 7. Difference Amplifier 4.2 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. 10006005 FIGURE 5. Indirectly Driving A Capacitive Load with DC Accuracy 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 15nA with 5V supply. Thus a 100kΩ input resistor will cause 1.5mV of error voltage. By balancing the resistor values at both inverting and non-inverting inputs, the error caused by the amplifier’s http:www.hgsemi.com.cn 14 2018 AUG LMV321/LMV358/LMV324 Application Notes 4.3 Single-Supply Inverting Amplifier (Continued) 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. 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-to-noise ratio in a low voltage system. 10006085 FIGURE 8. Three-op-amp Instrumentation Amplifier 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. 10006013 10006020 FIGURE 10. Single-Supply Inverting Amplifier 4.4 ACTIVE FILTER 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 (Figure 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. 4.4.1 Simple Low-Pass Active Filter The simple low-pass filter is shown in Figure 11. Its lowfrequency gain (ω → 0) is defined by -R3/R1. This allows low-frequency gains other than unity to be obtained. The filter has a -20dB/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. 10006011 10006035 FIGURE 9. Two-Op-amp Instrumentation Amplifier http:www.hgsemi.com.cn 15 2018 AUG LMV321/LMV358/LMV324 Application Notes Its transfer function is (Continued) (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 f c. 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 Comparison between the Equation (2) and Equation (3) yields 10006015 FIGURE 12. Frequency Response of Simple Low-Pass Active Filter in Figure 11 (4) 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: Slew Rate ≥ 0.5 x (ω HVOPP) x 10−6 V/µsec where ωH is the highest frequency of interest, and Vopp is the output peak-to-peak voltage. (5) 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 = 1rad/s, and C1 = C2 = Cn = 1F, and substitute these values into Equation (4) and Equation (5). From Equation (4), we obtain 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 (6) From Equation (5), we obtain (7) (1) http:www.hgsemi.com.cn 16 2018 AUG LMV321/LMV358/LMV324 Application Notes 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. (Continued) For minimum dc offset, V+ = V−, the resistor values at both inverting and non-inverting inputs should be equal, which means 4.4.3 2nd-order High Pass Filter A 2nd-order high pass filter can be built by simply interchanging those frequency selective components (R1, R 2, 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. (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 = 1KHz Start by selecting C1 and C2. Choose a standard value that is close to 10006083 FIGURE 14. Sallen-Key 2nd-Order Active High-Pass Filter From Equations (6), (7), (9), (10), R1= 1Ω R2= 1Ω R3= 4Ω R4= 4Ω The above resistor values are normalized values with ωn = 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 (kf) and impedance scaling factor (km). 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 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. Scaled values: R2 = R1 = 15.9 kΩ R3 = R4 = 63.6 kΩ C1 = C2 = 0.01 µF http:www.hgsemi.com.cn 17 2018 AUG LMV321/LMV358/LMV324 Application Notes (Continued) 10006039 FIGURE 15. State Variable Active Filter A design example for a bandpass filter is shown below: Assume the system design requires a bandpass filter with f O = 1kHz and Q = 50. What needs to be calculated are capacitor and resistor values. First choose convenient values for C1, R1 and R2: C1 = 1200pF 2R2 = R1 = 30kΩ Then from Equation (11), From Equation (12), where for all three filters, http:www.hgsemi.com.cn (11) From the above calculated values, the midband gain is H 0 = R3/R2 = 100 (40dB). The nearest 5% standard values have been added to Figure 15. (12) 4.5 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. 18 2018 AUG LMV321/LMV358/LMV324 Application Notes (Continued) 10006081 FIGURE 16. Pulse Generator 10006086 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 (= 0V 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 V OH. The capacitor starts to charge, and the cycle repeats itself. 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 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 R2. 10006077 FIGURE 18. Pulse Generator Figure 19 is a squarewave generator with the same path for charging and discharging the capacitor. http:www.hgsemi.com.cn 19 2018 AUG LMV321/LMV358/LMV324 Application Notes (Continued) 4.6.2 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. 10006076 FIGURE 19. Squarewave Generator 10006082 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. FIGURE 21. High Compliance Current Sink 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. 4.6.1 Fixed Current Source A multiple fixed current source is show in Figure 20. A voltage (VREF = 2V) is established across resistor R3 by the voltage divider (R3 and R 4). Negative feedback is used to cause the voltage drop across R 1 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 1mA reference value. 10006079 FIGURE 22. Power Amplifier 4.8 LED DRIVER The LMV321/358/324 can be used to drive an LED as shown in Figure 23. 10006084 10006080 FIGURE 20. Fixed Current Source http:www.hgsemi.com.cn FIGURE 23. LED Driver 20 2018 AUG LMV321/LMV358/LMV324 Application Notes 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 are single, dual and quad general purpose comparators for low voltage operation. (Continued) 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 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 LMV321/358/324 have rail-to-rail output, (VOH−VOL) equals to VS, which is the supply voltage. 10006078 FIGURE 24. Comparator with Hysteresis the VH = VS/(1+R2/R 1) Connection Diagrams 5-Pin SC70-5/SOT23-5 8-Pin SO/MSOP 14-Pin SO/TSSOP 10006001 Top View 10006002 Top View 10006003 Top View http:www.hgsemi.com.cn 21 2018 AUG