LF411 Low Offset, Low Drift JFET Input Operational Amplifier
April 1998
LF411 Low Offset, Low Drift JFET Input Operational Amplifier
General Description
These devices are low cost, high speed, JFET input operational amplifiers with very low input offset voltage and guaranteed input offset voltage drift. They require low supply current yet maintain a large gain bandwidth product and fast slew rate. In addition, well matched high voltage JFET input devices provide very low input bias and offset currents. The LF411 is pin compatible with the standard LM741 allowing designers to immediately upgrade the overall performance of existing designs. These amplifiers may be used in applications such as high speed integrators, fast D/A converters, sample and hold circuits and many other circuits requiring low input offset voltage and drift, low input bias current, high input impedance, high slew rate and wide bandwidth.
Features
Internally trimmed offset voltage: 0.5 mV(max) Input offset voltage drift: 10 µV/˚C(max) Low input bias current: 50 pA Low input noise current: Wide gain bandwidth: 3 MHz(min) High slew rate: 10V/µs(min) Low supply current: 1.8 mA High input impedance: 1012Ω Low total harmonic distortion AV = 10, RL = 10k, VO = 20 Vp-p, BW = 20 Hz−20 kHz: < 0.02% n Low 1/f noise corner: 50 Hz n Fast settling time to 0.01%: 2 µs n n n n n n n n n
Typical Connection
Connection Diagrams
Metal Can Package
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Note: Pin 4 connected to case.
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Top View Order Number LF411ACH or LF411MH/883 (Note 1) See NS Package Number H08A Dual-In-Line Package
Ordering Information
LF411XYZ X indicates electrical grade Y indicates temperature range “M” for military “C” for commercial Z indicates package type “H” or “N”
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Top View Order Number LF411ACN, LF411CN or LF411MJ/883 (Note 1) See NS Package Number N08E or J08A
BI-FET II™ is a trademark of National Semiconductor Corporation.
© 1999 National Semiconductor Corporation
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Simplified Schematic
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Note 1: Available per JM38510/11904
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Absolute Maximum Ratings (Note 2)
If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage Differential Input Voltage Input Voltage Range (Note 3) Output Short Circuit Duration Power Dissipation (Notes 4, 11) LF411A ± 22V ± 38V LF411 ± 18V ± 30V Tjmax θ jA
± 19V
Continuous H Package 670 mW
± 15V
Continuous N Package 670 mW (Note 6)
θjC Operating Temp. Range Storage Temp. Range Lead Temp. (Soldering, 10 sec.) ESD Tolerance
H Package 150˚C 162˚C/W (Still Air) 65˚C/W (400 LF/min Air Flow) 20˚C/W (Note 5) −65˚C≤TA≤150˚C 260˚C
N Package 115˚C 120˚C/W
(Note 5) −65˚C≤TA≤150˚C 260˚C Rating to be determined.
DC Electrical Characteristics
Symbol VOS ∆VOS/∆T IOS Parameter Input Offset Voltage Average TC of Input Offset Voltage Input Offset Current VS = ± 15V (Notes 6, 8) IB Input Bias Current VS = ± 15V (Notes 6, 8) RIN AVOL Input Resistance Large Signal Voltage Gain VO VCM CMRR PSRR IS Output Voltage Swing Input Common-Mode Voltage Range Common-Mode Rejection Ratio Supply Voltage Rejection Ratio Supply Current (Note 9) RS≤10k
Conditions Min RS = 10 kΩ, TA = 25˚C RS = 10 kΩ (Note 7) Tj = 25˚C Tj = 70˚C Tj = 125˚C Tj = 25˚C Tj = 70˚C Tj = 125˚C Tj = 25˚C VS = ± 15V, VO = ± 10V, RL = 2k, TA = 25˚C Over Temperature VS = ± 15V, RL = 10k
LF411A Typ 0.3 7 25 Max 0.5 10 100 2 25 50 200 4 50 1012 50 25 200 200 25 15 Min
LF411 Typ 0.8 7 25 Max 2.0 20 (Note 7) 100 2 25 50 200 4 50 1012 200 200
Units mV µV/˚C pA nA nA pA nA nA Ω V/mV V/mV V V V dB dB 3.4 mA
± 12 ± 16
80 80
± 13.5
+19.5 −16.5 100 100 1.8 2.8
± 12 ± 11
70 70
± 13.5
+14.5 −11.5 100 100 1.8
AC Electrical Characteristic
Symbol SR GBW en in Slew Rate Gain-Bandwidth Product Equivalent Input Noise Voltage Equivalent Input Noise Current Parameter
(Note 6) Conditions Min LF411A Typ 15 4 25 0.01 Max Min 8 2.7 10 3 LF411 Typ 15 4 25 0.01 Max V/µs MHz Units
VS = ± 15V, TA = 25˚C VS = ± 15V, TA = 25˚C TA = 25˚C, RS = 100Ω, f = 1 kHz TA = 25˚C, f = 1 kHz
Note 2: “Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is functional, but do not guarantee specific performance limits. Note 3: Unless otherwise specified the absolute maximum negative input voltage is equal to the negative power supply voltage.
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AC Electrical Characteristic
(Note 6) (Continued)
Note 4: For operating at elevated temperature, these devices must be derated based on a thermal resistance of θjA. Note 5: These devices are available in both the commercial temperature range 0˚C≤TA≤70˚C and the military temperature range −55˚C≤TA≤125˚C. 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 “H” package only. Note 6: Unless otherwise specified, the specifications apply over the full temperature range and for VS = ± 20V for the LF411A and for VS = ± 15V for the LF411. VOS, IB, and IOS are measured at VCM = 0. Note 7: The LF411A is 100% tested to this specification. The LF411 is sample tested to insure at least 90% of the units meet this specification. Note 8: The input bias currents are junction leakage currents which approximately double for every 10˚C increase in the junction temperature, Tj. Due to limited production test time, the input bias currents measured are correlated to junction temperature. In normal operation the junction temperature rises above the ambient temperature as a result of internal power dissipation, PD. Tj = TA+θjA PD where θjA is the thermal resistance from junction to ambient. Use of a heat sink is recommended if input bias current is to be kept to a minimum. Note 9: 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 LF411 and from ± 20V to ± 5V for the LF411A. Note 10: RETS 411X for LF411MH and LF411MJ military specifications. Note 11: Max. Power Dissipation is defined by the package characteristics. Operating the part near the Max. Power Dissipation may cause the part to operate outside guaranteed limits.
Typical Performance Characteristics
Input Bias Current Input Bias Current Supply Current
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Positive Common-Mode Input Voltage Limit
Negative Common-Mode Input Voltage Limit
Positive Current Limit
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Typical Performance Characteristics
Negative Current Limit
(Continued) Output Voltage Swing
Output Voltage Swing
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Gain Bandwidth
Bode Plot
Slew Rate
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Distortion vs Frequency
Undistorted Output Voltage Swing
Open Loop Frequency Response
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Typical Performance Characteristics
Common-Mode Rejection Ratio Power Supply Rejection Ratio
(Continued)
Equivalent Input Noise Voltage
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Open Loop Voltage Gain
Output Impedance
Inverter Settling Time
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Pulse Response
RL = 2 kΩ, CL10 pF Small Signal Non-Inverting
Small Signal Inverting
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Pulse Response
RL = 2 kΩ, CL10 pF (Continued) Large Signal Non-Inverting
Large Signal Inverting
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Current Limit (RL = 100Ω)
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Application Hints
The LF411 series of internally trimmed JFET input op amps ( BI-FET II™ ) provide very low input offset voltage and guaranteed input offset voltage drift. These JFETs have large reverse breakdown voltages from gate to source and drain eliminating the need for clamps across the inputs. Therefore, large differential input voltages can easily be accommodated without a large increase in input current. The maximum differential input voltage is independent of the supply voltages. However, neither of the input voltages should be allowed to exceed the negative supply as this will cause large currents to flow which can result in a destroyed unit. Exceeding the negative common-mode limit on either input will force the output to a high state, potentially causing a reversal of phase to the output. Exceeding the negative common-mode limit on both inputs will force the amplifier output to a high state. In neither case does a latch occur since raising the input back within the common-mode range again puts the input stage and thus the amplifier in a normal operating mode. Exceeding the positive common-mode limit on a single input will not change the phase of the output; however, if both inputs exceed the limit, the output of the amplifier may be forced to a high state. The amplifier 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 within 3V of the negative supply, an increase in input offset voltage may occur.
The LF411 is biased by a zener reference which allows normal circuit operation on ± 4.5V power supplies. Supply voltages less than these may result in lower gain bandwidth and slew rate. The LF411 will drive a 2 kΩ load resistance to ± 10V over the full temperature range. If the amplifier is forced to drive heavier load currents, however, an increase in input offset voltage may occur on the negative voltage swing and finally reach an active current limit on both positive and negative swings. Precautions should be taken to ensure that the power supply for the integrated circuit never becomes reversed in polarity or that the unit is not inadvertently installed backwards in a socket as an unlimited current surge through the resulting forward diode within the IC could cause fusing of the internal conductors and result in a destroyed unit. As with most amplifiers, care should be taken with lead dress, component placement and supply decoupling in order to ensure stability. For example, resistors from the output to an input should be placed with the body close to the input to minimize “pick-up” and maximize the frequency of the feedback pole by minimizing the capacitance from the input to ground. A feedback pole is created when the feedback around any amplifier is resistive. The parallel resistance and capacitance from the input of the device (usually the inverting input) to AC ground set the frequency of the pole. In many instances the frequency of this pole is much greater than the expected 3 dB frequency of the closed loop gain and consequently there is negligible effect on stability margin. However, if the feedback pole is less than approximately 6 times the expected 3 dB frequency, a lead capacitor should be placed
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Application Hints
(Continued)
from the output to the input of the op amp. The value of the added capacitor should be such that the RC time constant of this capacitor and the resistance it parallels is greater than or equal to the original feedback pole time constant.
Typical Applications
High Speed Current Booster
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PNP = 2N2905 NPN = 2N2219 unless noted TO-5 heat sinks for Q6-Q7
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Typical Applications
(Continued) 10-Bit Linear DAC with No VOS Adjust
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where AN = 1 if the AN digital input is high AN = 0 if the AN digital input is low
Single Supply Analog Switch with Buffered Output
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Detailed Schematic
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Physical Dimensions
inches (millimeters) unless otherwise noted
Metal Can Package (H) Order Number LF411MH/883 or LF411ACH NS Package Number H08A
Ceramic Dual-In-Line Package (J) Order Number LF411MJ/883 NS Package Number J08A
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LF411 Low Offset, Low Drift JFET Input Operational Amplifier
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
Molded Dual-In-Line Package (N) Order Number LF411ACN or LF411CN NS Package Number N08E
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