LF444 Quad Low Power JFET Input Operational Amplifier

LF444Quad Low Power JFET Input Operational AmplifierGeneral DescriptionFeaturesThe LF444 quad low power operational amplifier providesmany of the same AC characteristics as the industry standard LM148 while greatly improving the DC characteristicsof the LM148. The amplifier has the same bandwidth, slewrate, and gain (10 kΩ load) as the LM148 and only drawsone fourth the supply current of the LM148. In addition thewell matched high voltage JFET input devices of the LF444reduce the input bias and offset currents by a factor of10,000 over the LM148. The LF444 also has a very lowequivalent input noise voltage for a low power amplifier.The LF444 is pin compatible with the LM148 allowing animmediate 4 times reduction in power drain in many applications. The LF444 should be used wherever low powerdissipation and good electrical characteristics are the majorconsiderations.nnnnnnnnSimplified SchematicZ indicates package type “D”, “M” or “N” supply current of a LM148: 200 µA/Amplifier (max)Low input bias current: 50 pA (max)High gain bandwidth: 1 MHzHigh slew rate: 1 V/µsLow noise voltage for low powerLow input noise currentHigh input impedance: 1012ΩHigh gain: 50k (min)14Connection Diagram1/4 QuadDual-In-Line Package0091560100915602Top ViewOrder Number LF444CM, LF444CMX,LF444ACN, LF 444CN or LF444MD/883See NS Package Number D14E, M14A or N14AOrdering InformationLF444XYZX indicates electrical gradeY indicates temperature range“M” for military, “C” for commercialBI-FET and BI-FET II are trademarks of National Semiconductor Corporation. 2004 National Semiconductor CorporationDS009156www.national.comLF444 Quad Low Power JFET Input Operational AmplifierAugust 2000

LF444Absolute Maximum Ratings (Note 11)LF444A/LF444Operating Temperature RangeIf Military/Aerospace specified devices are required,please contact the National Semiconductor Sales Office/Distributors for availability and specifications.LF444ALF444 22V 38V 19V 18V 30V 15VContinuousContinuousSupply VoltageDifferential Input VoltageInput Voltage RangeESD Tolerance (Note 10)Soldering InformationDual-In-Line Packages(Soldering, 10 sec.)Duration (Note 2)D PackageN, M Packages900 mW670 mW150 C115 C100 C/W85 C/WPower DissipationθjA (Typical)DC Electrical CharacteristicsParameterVapor Phase (60 sec.)215 CInfrared (15 sec.)220 CSee AN-450 “Surface Mounting Methods and Their Effect onProduct Reliability” for other methods of soldering surfacemount devices.(Notes 3, 9)Tj max(Note 5)ConditionsLF444AMinInput Offset VoltageRS 10k, TA 25 CMax25MinUnitsTypMax310mV12mV6.5 55 C TA 125 CAverage TC of InputLF444Typ0 C TA 70 C VOS/ T260 CSmall Outline PackageOutput Short CircuitVOSRating tobe determined(Note 1)Symbol(Note 4) 65 C TA 150 CStorage Temperature Range8RS 10 kΩmV1010µV/ COffset VoltageIOSIBInput Offset CurrentInput Bias CurrentVS 15VTj 25 C(Notes 5, 6)Tj 70 C1.5Tj 125 C10VS 15VTj 25 C(Notes 5, 6)Tj 70 C510AVOLInput ResistanceTj 25 CLarge Signal VoltageVS 15V, VO 10VGainRL 10 kΩ, TA 25 CVOOutput Voltage SwingInput Common-ModeCommon-Mode5010010nA100pA3nAnA2525 12 16Voltage RangeCMRRpA2050VS 15V, RL 10 kΩ501.5nA1012Over TemperatureVCM53Tj 125 CRIN251012Ω100V/mV15 13 12 11 18 17V/mV 13V 14V 12VRS 10 kΩ801007095dB(Note 7)801007090dBRejection RatioPSRRSupply VoltageRejection RatioISSupply Currentwww.national.com0.620.80.61.0mA

SymbolParameterLF444AC Electrical Characteristics(Note 4MaxMinTyp 120 120UnitsMaxdBCouplingSRSlew RateVS 15V, TA 25 C11V/µsGBWGain-Bandwidth ProductVS 15V, TA 25 C11MHzenEquivalent Input Noise VoltageTA 25 C, RS 100Ω,3535inEquivalent Input Noise CurrentTA 25 C, f 1 kHz0.010.01f 1 kHzNote 1: Unless otherwise specified the absolute maximum negative input voltage is equal to the negative power supply voltage.Note 2: Any of the amplifier outputs can be shorted to ground indefinitely, however, more than one should not be simultaneously shorted as the maximum junctiontemperature will be exceeded.Note 3: For operating at elevated temperature, these devices must be derated based on a thermal resistance of θjA.Note 4: The LF444A is available in both the commercial temperature range 0 C TA 70 C and the military temperature range 55 C TA 125 C. The LF444is available in the commercial temperature range only. The temperature range is designated by the position just before the package type in the device number. A“C” indicates the commercial temperature range and an “M” indicates the military temperature range. The military temperature range is available in “D” package only.Note 5: Unless otherwise specified the specifications apply over the full temperature range and for VS 20V for the LF444A and for VS 15V for the LF444.VOS, IB, and IOS are measured at VCM 0.Note 6: The input bias currents are junction leakage currents which approximately double for every 10 C increase in the junction temperature, Tj. Due to limitedproduction test time, the input bias currents measured are correlated to junction temperature. In normal operation the junction temperature rises above the ambienttemperature as a result of internal power dissipation, PD. Tj TA θjAPD where θjA is the thermal resistance from junction to ambient. Use of a heat sink isrecommended if input bias current is to be kept to a minimum.Note 7: Supply voltage rejection ratio is measured for both supply magnitudes increasing or decreasing simultaneously in accordance with common practice from 15V to 5V for the LF444 and from 20V to 5V for the LF444A.Note 8: Refer to RETS444X for LF444MD military specifications.Note 9: Max. Power Dissipation is defined by the package characteristics. Operating the part near the Max. Power Dissipation may cause the part to operate outsideguaranteed limits.Note 10: Human body model, 1.5 kΩ in series with 100 pF.Note 11: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating ratings indicate conditions for which the device isfunctional, but do not guarantee specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions whichguarantee specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not guaranteed for parameters where no limitis given, however, the typical value is a good indication of device performance.Typical Performance CharacteristicsInput Bias CurrentInput Bias Current00915612009156133www.national.com

LF444Typical Performance Characteristics(Continued)Positive Common-ModeInput Voltage LimitSupply Current0091561500915614Negative Common-ModeInput Voltage LimitPositive Current Limit0091561700915616Negative Current LimitOutput Voltage Swing0091561900915618www.national.com4

LF444Typical Performance Characteristics(Continued)Output Voltage SwingGain Bandwidth0091562100915620Bode PlotSlew Rate0091562300915622Undistorted OutputVoltage SwingDistortion vs Frequency00915624009156255www.national.com

LF444Typical Performance Characteristics(Continued)Open LoopFrequency ResponseCommon-ModeRejection Ratio0091562600915627Power SupplyRejection RatioEquivalent InputNoise Voltage0091562800915629Open Loop Voltage GainOutput Impedance00915630www.national.com009156316

LF444Typical Performance Characteristics(Continued)Inverter Settling Time00915632Pulse ResponseRL 10 kΩ, CL 10 pFLarge Signal InvertingSmall Signal Inverting0091560800915606Large Signal Non-InvertingSmall Signal Non-Inverting0091560900915607Application HintsThis device is a quad low power op amp with JFET inputdevices ( BI-FET ). These JFETs have large reverse breakdown voltages from gate to source and drain eliminating theneed for clamps across the inputs. Therefore, large differential input voltages can easily be accommodated without alarge increase in input current. The maximum differentialinput voltage is independent of the supply voltages. However, neither of the input voltages should be allowed toexceed the negative supply as this will cause large currentsto flow which can result in a destroyed unit.7www.national.com

LF444Application HintsPrecautions should be taken to ensure that the power supplyfor the integrated circuit never becomes reversed in polarityor that the unit is not inadvertently installed backwards in asocket as an unlimited current surge through the resultingforward diode within the IC could cause fusing of the internalconductors and result in a destroyed unit.(Continued)Exceeding the negative common-mode limit on either inputwill force the output to a high state, potentially causing areversal of phase to the output. Exceeding the negativecommon-mode limit on both inputs will force the amplifieroutput to a high state. In neither case does a latch occursince raising the input back within the common-mode rangeagain puts the input stage and thus the amplifier in a normaloperating mode.Exceeding the positive common-mode limit on a single inputwill not change the phase of the output; however, if bothinputs exceed the limit, the output of the amplifier will beforced to a high state.The amplifiers will operate with a common-mode input voltage equal to the positive supply; however, the gain bandwidth and slew rate may be decreased in this condition.When the negative common-mode voltage swings to within3V of the negative supply, an increase in input offset voltagemay occur.Each amplifier is individually biased to allow normal circuitoperation with power supplies of 3.0V. Supply voltages lessthan these may degrade the common-mode rejection andrestrict the output voltage swing.The amplifiers will drive a 10 kΩ load resistance to 10Vover the full temperature range. If the amplifier is forced todrive heavier load currents, however, an increase in inputoffset voltage may occur on the negative voltage swing andfinally reach an active current limit on both positive andnegative swings.www.national.comAs with most amplifiers, care should be taken with leaddress, component placement and supply decoupling in orderto ensure stability. For example, resistors from the output toan input should be placed with the body close to the input tominimize “pick-up” and maximize the frequency of the feedback pole by minimizing the capacitance from the input toground.A feedback pole is created when the feedback around anyamplifier is resistive. The parallel resistance and capacitancefrom the input of the device (usually the inverting input) to ACground set the frequency of the pole. In many instances thefrequency of this pole is much greater than the expected 3dB frequency of the closed loop gain and consequently thereis negligible effect on stability margin. However, if the feedback pole is less than approximately 6 times the expected 3dB frequency a lead capacitor should be placed from theoutput to the input of the op amp. The value of the addedcapacitor should be such that the RC time constant of thiscapacitor and the resistance it parallels is greater than orequal to the original feedback pole time constant.8

LF444Typical ApplicationpH Probe Amplifier/Temperature Compensator00915610***For R2 50k, R4 330k 1%For R2 100k, R4 75k 1%For R2 200k, R4 56k 1%**Polystyrene*Film resistor type RN60CTo calibrate, insert probe in pH 7 solution. Set the “TEMPERATURE ADJUST” pot, R2, to correspond to the solution temperature: full clockwise for 0 C, andproportionately for intermediate temperatures, using a turns-counting dial. Then set “CALIBRATE” pot so output reads 7V.Typical probe Ingold Electrodes #465-359www.national.com

LF444Detailed Schematic1/4 Quad00915611www.national.com10

LF444Physical Dimensionsinches (millimeters)unless otherwise notedOrder Number LF444MD/883See NS Package Number D14EOrder Number LF444CM or LF444CMXSee NS Package Number M14A11www.national.com