TL081

TL081 Wide Bandwidth JFET Input Operational Amplifier December 1995 TL081 Wide Bandwidth JFET Input Operational Amplifier General Description The TL081 is a low cost high speed JFET input operational amplifier with an internally trimmed input offset voltage (BI-FET IITM technology) The device requires a low supply current and yet maintains a large gain bandwidth product and a fast slew rate In addition well matched high voltage JFET input devices provide very low input bias and offset currents The TL081 is pin compatible with the standard LM741 and uses the same offset voltage adjustment circuitry This feature allows designers to immediately upgrade the overall performance of existing LM741 designs The TL081 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 low input bias current high input impedance high slew rate and wide bandwidth The devices has low noise and offset voltage drift but for applications where these requirements are critical the LF356 is recommended If maximum supply current is important however the TL081C is the better choice Features Y Y Y Y Y Y Y Y Y Y Y Internally trimmed offset voltage Low input bias current Low input noise voltage Low input noise current Wide gain bandwidth High slew rate Low supply current High input impedance Low total harmonic distortion AV e 10 RL e 10k VO e 20 Vp-p BW e 20 Hzb20 kHz Low 1 f noise corner Fast settling time to 0 01% 15 mV 50 pA 25 nV 0Hz 0 01 pA 0Hz 4 MHz 13 V ms 1 8 mA 1012X k 0 02% 50 Hz 2 ms Typical Connection Simplified Schematic TL H 8358 – 1 Connection Diagram Dual-In-Line Package TL H 8358 – 2 TL H 8358 – 4 Order Number TL081CP See NS Package Number N08E BI-FET IITM is a trademark of National Semiconductor Corp C1995 National Semiconductor Corporation TL H 8358 RRD-B30M125 Printed in U S A Absolute Maximum Ratings If Military Aerospace specified devices are required please contact the National Semiconductor Sales Office Distributors for availability and specifications Supply Voltage Power Dissipation (Notes 1 and 6) Operating Temperature Range Tj(MAX) Differential Input Voltage g 18V Input Voltage Range (Note 2) Output Short Circuit Duration Storage Temperature Range Lead Temp (Soldering 10 seconds) ijA ESD rating to be determined g 15V Continuous b 65 C to a 150 C 670 mW 0 C to a 70 C 115 C g 30V 260 C 120 C W DC Electrical Characteristics (Note 3) Symbol VOS DVOS DT IOS IB RIN AVOL Parameter Input Offset Voltage Average TC of Input Offset Voltage Input Offset Current Input Bias Current Input Resistance Large Signal Voltage Gain Conditions Min RS e 10 kX TA e 25 C Over Temperature RS e 10 kX Tj e 25 C (Notes 3 4) Tj s 70 C Tj e 25 C (Notes 3 4) Tj s 70 C Tj e 25 C VS e g 15V TA e 25 C VO e g 10V RL e 2 kX Over Temperature VO VCM CMRR PSRR IS Output Voltage Swing Input Common-Mode Voltage Range Common-Mode Rejection Ratio Supply Voltage Rejection Ratio Supply Current VS e g 15V RL e 10 kX VS e g 15V RS s 10 kX (Note 5) 25 15 g 12 g 11 g 13 5 TL081C Typ 5 Max 15 20 Units mV mV mV C 100 4 200 8 pA nA pA nA X V mV V mV V V V dB dB 28 mA 10 25 50 1012 100 a 15 b 12 70 70 100 100 18 AC Electrical Characteristics (Note 3) Symbol SR GBW en in Parameter Slew Rate Gain Bandwidth Product Equivalent Input Noise Voltage Equivalent Input Noise Current Conditions Min VS e g 15V TA e 25 C VS e g 15V TA e 25 C TA e 25 C RS e 100X f e 1000 Hz Tj e 25 C f e 1000 Hz TL081C Typ 13 4 25 0 01 Max V ms MHz nV 0Hz pA 0Hz Units Note 1 For operating at elevated temperature the device must be derated based on a thermal resistance of 120 C W junction to ambient for N package Note 2 Unless otherwise specified the absolute maximum negative input voltage is equal to the negative power supply voltage Note 3 These specifications apply for VS e g 15V and 0 C s TA s a 70 C VOS IB and IOS are measured at VCM e 0 Note 4 The input bias currents are junction leakage currents which approximately double for every 10 C increase in the junction temperature Tj Due to the 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 e TA a ijA PD where ijA 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 5 Supply voltage rejection ratio is measured for both supply magnitudes increasing or decreasing simultaneously in accordance with common practice from VS e g 5V to g 15V Note 6 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 2 Typical Performance Characteristics Input Bias Current Input Bias Current Supply Current Positive Common-Mode Input Voltage Limit Negative Common-Mode Input Voltage Limit Positive Current Limit Negative Current Limit Voltage Swing Output Voltage Swing Gain Bandwidth Bode Plot Slew Rate TL H 8358 – 5 3 Typical Performance Characteristics Distortion vs Frequency (Continued) Open Loop Frequency Response Undistorted Output Voltage Swing Common-Mode Rejection Ratio Power Supply Rejection Ratio Equivalent Input Noise Voltage Open Loop Voltage Gain (V V) Output Impedance Inverter Settling Time TL H 8358 – 6 4 Pulse Response Small Signal Inverting Small Signal Non-Inverting TL H 8358 – 7 TL H 8358 – 13 Large Signal Inverting Large Signal Non-Inverting TL H 8358 – 14 TL H 8358 – 15 Current Limit (RL e 100X) TL H 8358 – 16 Application Hints The TL081 is an op amp with an internally trimmed input offset voltage and JFET input devices (BI-FET II) 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 5 Application Hints (Continued) 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 will 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 TL081 is biased by a zener reference which allows normal circuit operation on g 4V power supplies Supply voltages less than these may result in lower gain bandwidth and slew rate The TL081 will drive a 2 kX load resistance to g 10V over the full temperature range of 0 C to a 70 C 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 Because these amplifiers are JFET rather than MOSFET input op amps they do not require special handling 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 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 Detailed Schematic TL H 8358 – 8 6 Typical Applications Supply Current Indicator Limiter Hi-ZIN Inverting Amplifier TL H 8358 – 9  VOUT switches high when RSIS l VD TL H 8358 – 10 Parasitic input capacitance C1 j (3 pF for TL081 plus any additional layout capacitance) interacts with feedback elements and creates undesirable high frequency pole To compensate add C2 such that R2C2 j R1C1 Ultra-Low (or High) Duty Cycle Pulse Generator Long Time Integrator TL H 8358–11  tOUTPUT HIGH  tOUTPUT LOW 4 8 b 2VS R1C fin 4 8 b VS 2VS b 7 8 R2C fin VS b 7 8 Low leakage capacitor TL H 8358 – 12  50k pot used for less sensitive VOS adjust where VS e V a a l Vb l low leakage capacitor 7 TL081 Wide Bandwidth JFET Input Operational Amplifier Physical Dimensions inches (millimeters) Molded Dual-In-Line Package (N) Order Number TL081CP NS Package Number N08E LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT OF NATIONAL SEMICONDUCTOR CORPORATION As used herein 1 Life support devices or systems are devices or systems which (a) are intended for surgical implant into the body or (b) support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the labeling can be reasonably expected to result in a significant injury to the user National Semiconductor Corporation 1111 West Bardin Road Arlington TX 76017 Tel 1(800) 272-9959 Fax 1(800) 737-7018 2 A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure 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