LF356N/NOPB

Product Folder Sample & Buy Support & Community Tools & Software Technical Documents LF155, LF156, LF256, LF257 LF355, LF356, LF357 SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 LFx5x JFET Input Operational Amplifiers 1 Features 2 Applications • • • • • • • • 1 • • Advantages – Replace Expensive Hybrid and Module FET Op Amps – Rugged JFETs Allow Blow-Out Free Handling Compared With MOSFET Input Devices – Excellent for Low Noise Applications Using Either High or Low Source Impedance—Very Low 1/f Corner – Offset Adjust Does Not Degrade Drift or Common-Mode Rejection as in Most Monolithic Amplifiers – New Output Stage Allows Use of Large Capacitive Loads (5,000 pF) Without Stability Problems – Internal Compensation and Large Differential Input Voltage Capability Common Features – Low Input Bias Current: 30 pA – Low Input Offset Current: 3 pA – High Input Impedance: 1012 Ω – Low Input Noise Current: 0.01 pA/√Hz – High Common-Mode Rejection Ratio: 100 dB – Large DC Voltage Gain: 106 dB Uncommon Features – Extremely Fast Settling Time to 0.01%: – 4 μs for the LFx55 devices – 1.5 μs for the LFx56 – 1.5 μs for the LFx57 (AV = 5) – Fast Slew Rate: – 5 V/µs for the LFx55 – 12 V/µs for the LFx56 – 50 V/µs for the LFx57 (AV = 5) – Wide Gain Bandwidth: – 2.5 MHz for the LFx55 devices – 5 MHz for the LFx56 – 20 MHz for the LFx57 (AV = 5) – Low Input Noise Voltage: – 20 nV/√Hz for the LFx55 – 12 nV/√Hz for the LFx56 – 12 nV/√Hz for the LFx57 (AV = 5) Precision High-Speed Integrators Fast D/A and A/D Converters High Impedance Buffers Wideband, Low Noise, Low Drift Amplifiers Logarithmic Amplifiers Photocell Amplifiers Sample and Hold Circuits 3 Description The LFx5x devices are the first monolithic JFET input operational amplifiers to incorporate well-matched, high-voltage JFETs on the same chip with standard bipolar transistors (BI-FET™ Technology). These amplifiers feature low input bias and offset currents/low offset voltage and offset voltage drift, coupled with offset adjust, which does not degrade drift or common-mode rejection. The devices are also designed for high slew rate, wide bandwidth, extremely fast settling time, low voltage and current noise and a low 1/f noise corner. Device Information(1) PART NUMBER LFx5x PACKAGE BODY SIZE (NOM) SOIC (8) 4.90 mm × 3.91 mm TO-CAN (8) 9.08 mm × 9.08 mm PDIP (8) 9.81 mm × 6.35 mm (1) For all available packages, see the orderable addendum at the end of the data sheet. Simplified Schematic 3 pF in LF357 series 1 An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications, intellectual property matters and other important disclaimers. PRODUCTION DATA. LF155, LF156, LF256, LF257 LF355, LF356, LF357 SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 www.ti.com Table of Contents 1 2 3 4 5 6 1 1 1 2 3 4 8 6.1 6.2 6.3 6.4 6.5 4 4 4 5 9 Power Supply Recommendations...................... 33 10 Layout................................................................... 33 5 11 Device and Documentation Support ................. 35 6.6 6.7 6.8 6.9 7 7.2 Functional Block Diagram ....................................... 15 7.3 Feature Description................................................. 16 7.4 Device Functional Modes........................................ 16 Features .................................................................. Applications ........................................................... Description ............................................................. Revision History..................................................... Pin Configuration and Functions ......................... Specifications......................................................... Absolute Maximum Ratings ...................................... ESD Ratings.............................................................. Recommended Operating Conditions....................... Thermal Information .................................................. AC Electrical Characteristics, TA = TJ = 25°C, VS = ±15 V.......................................................................... DC Electrical Characteristics, TA = TJ = 25°C, VS = ±15 V.......................................................................... DC Electrical Characteristics .................................... Power Dissipation Ratings ........................................ Typical Characteristics .............................................. Application and Implementation ........................ 17 8.1 Application Information............................................ 17 8.2 Typical Application .................................................. 18 8.3 System Examples ................................................... 20 10.1 Layout Guidelines ................................................. 33 10.2 Layout Example .................................................... 34 11.1 11.2 11.3 11.4 11.5 6 6 7 8 Detailed Description ............................................ 14 7.1 Overview ................................................................. 14 Related Links ........................................................ Community Resources.......................................... Trademarks ........................................................... Electrostatic Discharge Caution ............................ Glossary ................................................................ 35 35 35 35 35 12 Mechanical, Packaging, and Orderable Information ........................................................... 35 4 Revision History NOTE: Page numbers for previous revisions may differ from page numbers in the current version. Changes from Revision C (March 2013) to Revision D Page • Added Pin Configuration and Functions section, ESD Ratings table, Thermal Information table, Feature Description section, Device Functional Modes, Application and Implementation section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and Mechanical, Packaging, and Orderable Information section ................................................................................................................................................................ 1 • Removed THIGH parameter as it is redundant to TA maximum ............................................................................................... 4 Changes from Revision B (March 2013) to Revision C • 2 Page Changed layout of National Data Sheet to TI format ........................................................................................................... 31 Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 LF155, LF156, LF256, LF257 LF355, LF356, LF357 www.ti.com SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 5 Pin Configuration and Functions LMC Package 8-Pin TO-99 Top View D or P Package 8-Pin SOIC or PDIP Top View Available per JM38510/11401 or JM38510/11402 Pin Functions PIN NAME NO. BALANCE I/O DESCRIPTION 1, 5 I Balance for input offset voltage +INPUT 3 I Noninverting input –INPUT 2 I Inverting input NC 8 — No connection OUTPUT 6 O Output V+ 7 — Positive power supply V– 4 — Negative power supply Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 3 LF155, LF156, LF256, LF257 LF355, LF356, LF357 SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 www.ti.com 6 Specifications 6.1 Absolute Maximum Ratings over operating free-air temperature range (unless otherwise noted) (1) (2) (3) MIN Supply voltage Differential input voltage Input voltage (4) ±22 LF35x ±18 LF15x, LF25x, LF356B ±40 LF35x ±30 LF15x, LF25x, LF356B ±20 LF35x ±16 Output short circuit duration TJMAX LF15x 150 LF25x, LF356B, LF35x 115 P package LF25x, LF356B, LF35x 100 D package LF25x, LF356B, LF35x 100 TO-99 package Soldering (10 sec.) PDIP package Soldering (10 sec.) SOIC package (2) (3) (4) V V V — °C 300 260 Vapor phase (60 sec.) LF25x, LF356B, LF35x Infrared (15 sec.) LF25x, LF356B, LF35x °C 215 220 −65 Storage temperature, Tstg (1) UNIT Continuous LMC package Soldering information (lead temp.) MAX LF155x, LF256x, LF356B 150 °C Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. The maximum power dissipation for these devices must be derated at elevated temperatures and is dictated by TJMAX, θJA, and the ambient temperature, TA. The maximum available power dissipation at any temperature is PD = (TJMAX − TA) / θJA or the 25°C PdMAX, whichever is less. If Military/Aerospace specified devices are required, contact the TI Sales Office/Distributors for availability and specifications. Unless otherwise specified the absolute maximum negative input voltage is equal to the negative power supply voltage. 6.2 ESD Ratings V(ESD) (1) (2) Electrostatic discharge Human body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1) (2) VALUE UNIT ±1000 V JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. 100 pF discharged through 1.5-kΩ resistor 6.3 Recommended Operating Conditions over operating free-air temperature range (unless otherwise noted) Supply voltage, VS MIN NOM MAX LF15x ±15 VS ±20 LF25x ±15 VS ±20 LF356B ±15 VS ±20 LF35x TA 4 UNIT V ±15 LF15x –55 TA 125 LF25x –25 TA 85 LF356B 0 TA 70 LF35x 0 TA 70 Submit Documentation Feedback °C Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 LF155, LF156, LF256, LF257 LF355, LF356, LF357 www.ti.com SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 6.4 Thermal Information LF155, LF156, LF355, LF357 THERMAL METRIC (1) LF356 P (PDIP) D (SOIC) LMC (TO-99) P (PDIP) 8 PINS 8 PINS 8 PINS 8 PINS Junction-to-ambient thermal resistance UNIT 130 195 — 55.2 Still Air — — 160 — 400 LF/Min Air Flow — — 65 — RθJC(top) Junction-to-case (top) thermal resistance — — 23 44.5 °C/W RθJB Junction-to-board thermal resistance — — — 32.4 °C/W ψJT Junction-to-top characterization parameter — — — 21.7 °C/W ψJB Junction-to-board characterization parameter — — — 32.3 °C/W RθJA (1) °C/W For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application report, SPRA953. 6.5 AC Electrical Characteristics, TA = TJ = 25°C, VS = ±15 V PARAMETER TEST CONDITIONS MIN LFx55 SR Slew Rate LF15x: AV = 1 LFx56, LF356B LFx56, LF356B LF357: AV = 5 LFx57 LFx55 GBW ts Gain Bandwidth Product Settling Time to 0.01% (1) en MAX UNIT 5 7.5 12 V/μs 50 2.5 LFx56, LF356B 5 LFx57 20 LFx55 4 LFx56, LF356B 1.5 LFx57 1.5 f = 100 Hz Equivalent Input Noise Voltage TYP RS = 100 Ω f = 1000 Hz LFx55 25 LFx56, LF356B 15 LFx57 15 LFx55 20 LFx56, LF356B 12 LFx57 12 MHz μs nV/√Hz nV/√Hz LFx55 f = 100 Hz in LFx56, LF356B 0.01 pA/√Hz 0.01 pA/√Hz LFx57 Equivalent Input Current Noise LFx55 f = 1000 Hz LFx56, LF356B LFx57 LFx55 CIN Input Capacitance LFx56, LF356B 3 pF LFx57 (1) Settling time is defined here, for a unity gain inverter connection using 2-kΩ resistors for the LF15x. It is the time required for the error voltage (the voltage at the inverting input pin on the amplifier) to settle to within 0.01% of its final value from the time a 10-V step input is applied to the inverter. For the LF357, AV = −5, the feedback resistor from output to input is 2 kΩ and the output step is 10 V (See Settling Time Test Circuit). Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 5 LF155, LF156, LF256, LF257 LF355, LF356, LF357 SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 www.ti.com 6.6 DC Electrical Characteristics, TA = TJ = 25°C, VS = ±15 V PARAMETER TEST CONDITIONS Supply current TYP MAX LF155 MIN 2 4 LF355 2 4 LFx56, LF356B 5 7 LF356 5 10 LF357 5 10 UNIT mA 6.7 DC Electrical Characteristics See (1) PARAMETER TEST CONDITIONS TA = 25°C VOS RS = 50 Ω Input offset voltage TYP MAX LF15x, LF25x, LF356B MIN 3 5 LF35x 3 10 LF15x Over temperature 7 LF25x, LF356B 6.5 LF35x 13 ΔVOS/ΔT Average TC of input offset voltage RS = 50 Ω LF15x, LF25x, LF356B, LF35x 5 ΔTC/ΔVOS Change in average TC with VOS adjust RS = 50 Ω (2) LF15x, LF25x, LF356B, LF35x 0.5 TJ = 25°C (1) IOS (3) Input offset current TJ = 25°C (1) IB (3) Input bias current RIN AVOL VO (1) (2) (3) 6 Input resistance TJ = 25°C Large signal voltage gain VS = ±15 V, VO = ±10 V, RL = 2 kΩ Output voltage swing 3 20 3 50 Over temperature pA 20 LF25x, LF356B 1 LF35x 2 LF15x, LF25x, LF356B 30 100 LF35x 30 200 nA pA 50 LF25x, LF356B 5 LF35x 8 1012 LF15x, LF25x, LF356B, LF35x TA = 25°C μV/°C per mV LF35x LF15x TJ ≤ THIGH mV μV/°C LF15x, LF25x, LF356B LF15x TJ ≤ THIGH UNIT LF15x, LF25x, LF356B 50 200 LF35x 25 200 LF15x, LF25x, LF356B 25 LF35x nA Ω V/mV 15 VS = ±15 V, RL = 10 kΩ LF15x, LF25x, LF356B, LF35x ±12 ±13 VS = ±15 V, RL= 2 kΩ LF15x, LF25x, LF356B, LF35x ±10 ±12 V Unless otherwise stated, these test conditions apply: LF15x LF25x LF356B LF35x Supply Voltage, VS ±15 V ≤ VS ≤ ±20 V ±15 V ≤ VS ≤ ±20 V ±15 V ≤ VS ≤ ±20 V VS = ±15 V TA −55°C ≤ TA ≤ +125°C −25°C ≤ TA ≤ +85°C 0°C ≤ TA ≤ +70°C 0°C ≤ TA ≤ +70°C THIGH +125°C +85°C +70°C +70°C and VOS, IB and IOS are measured at VCM = 0. The Temperature Coefficient of the adjusted input offset voltage changes only a small amount (0.5 μV/°C typically) for each mV of adjustment from its original unadjusted value. Common-mode rejection and open-loop voltage gain are also unaffected by offset adjustment. 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. Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 LF155, LF156, LF256, LF257 LF355, LF356, LF357 www.ti.com SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 DC Electrical Characteristics (continued) See (1) PARAMETER TEST CONDITIONS VCM, High Input common-mode voltage range VCM VS = ±15 V MIN TYP LF15x, LF25x, LF356B 11 15.1 LF35x 10 15.1 LF15x, LF25x, LF356B VCM, Low LF35x −12 –11 −12 –10 CMRR Common-mode rejection ratio LF15x, LF25x, LF356B LF35x 80 100 PSRR Supply voltage rejection ratio (4) LF15x, LF25x, LF356B 85 100 LF35x 80 100 (4) MAX 85 100 UNIT V dB dB Supply Voltage Rejection is measured for both supply magnitudes increasing or decreasing simultaneously, in accordance with common practice. 6.8 Power Dissipation Ratings MIN LMC Package (Still Air) Power Dissipation at TA = 25°C (1) (2) (1) (2) MAX LF15x 560 LF25x, LF356B, LF35x 400 LMC Package (400 LF/Min Air Flow) LF15x 1200 LF25x, LF356B, LF35x 1000 P Package LF25x, LF356B, LF35x 670 D Package LF25x, LF356B, LF35x 380 UNIT mW The maximum power dissipation for these devices must be derated at elevated temperatures and is dictated by TJMAX, θJA, and the ambient temperature, TA. The maximum available power dissipation at any temperature is PD = (TJMAX − TA) / θJA or the 25°C PdMAX, whichever is less. Maximum power dissipation is defined by the package characteristics. Operating the part near the maximum power dissipation may cause the part to operate outside specified limits. Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 7 LF155, LF156, LF256, LF257 LF355, LF356, LF357 SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 www.ti.com 6.9 Typical Characteristics 6.9.1 Typical DC Performance Characteristics Curves are for LF155 and LF156 unless otherwise specified. 8 Figure 1. Input Bias Current Figure 2. Input Bias Current Figure 3. Input Bias Current Figure 4. Voltage Swing Figure 5. Supply Current Figure 6. Supply Current Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 LF155, LF156, LF256, LF257 LF355, LF356, LF357 www.ti.com SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 Typical DC Performance Characteristics (continued) Curves are for LF155 and LF156 unless otherwise specified. Figure 7. Negative Current Limit Figure 8. Positive Current Limit Figure 9. Positive Common-Mode Input Voltage Limit Figure 10. Negative Common-Mode Input Voltage Limit Figure 11. Open-Loop Voltage Gain Figure 12. Output Voltage Swing Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 9 LF155, LF156, LF256, LF257 LF355, LF356, LF357 SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 www.ti.com 6.9.2 Typical AC Performance Characteristics 10 Figure 13. Gain Bandwidth Figure 14. Gain Bandwidth Figure 15. Normalized Slew Rate Figure 16. Output Impedance Figure 17. Output Impedance Figure 18. LF155 Small Signal Pulse Response, AV = +1 Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 LF155, LF156, LF256, LF257 LF355, LF356, LF357 www.ti.com SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 Typical AC Performance Characteristics (continued) Figure 19. LF156 Small Signal Pulse Response, AV = +1 Figure 20. LF155 Large Signal Pulse Response, AV = +1 Figure 21. LF156 Large Signal Puls Response, AV = +1 Figure 22. Inverter Settling Time Figure 23. Inverter Settling Time Figure 24. Open-Loop Frequency Response Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 11 LF155, LF156, LF256, LF257 LF355, LF356, LF357 SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 www.ti.com Typical AC Performance Characteristics (continued) 12 Figure 25. Bode Plot Figure 26. Bode Plot Figure 27. Bode Plot Figure 28. Common-Mode Rejection Ratio Figure 29. Power Supply Rejection Ratio Figure 30. Power Supply Rejection Ratio Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 LF155, LF156, LF256, LF257 LF355, LF356, LF357 www.ti.com SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 Typical AC Performance Characteristics (continued) Figure 31. Undistorted Output Voltage Swing Figure 32. Equivalent Input Noise Voltage Figure 33. Equivalent Input Noise Voltage (Expanded Scale) Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 13 LF155, LF156, LF256, LF257 LF355, LF356, LF357 SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 www.ti.com 7 Detailed Description 7.1 Overview These are the first monolithic JFET input operational amplifiers to incorporate well matched, high voltage JFETs on the same chip with standard bipolar transistors (BI-FET Technology). These amplifiers feature low input bias and offset currents, as well as low offset voltage and offset voltage drift, coupled with offset adjust which does not degrade drift or common-mode rejection. These devices can replace expensive hybrid and module FET operational amplifiers. Designed for low voltage and current noise and a low 1/f noise corner, these devices are excellent for low noise applications using either high or low source impedance. 14 Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 LF155, LF156, LF256, LF257 LF355, LF356, LF357 www.ti.com SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 7.2 Functional Block Diagram *C = 3 pF in LF357 series. Figure 34. Detailed Schematic Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 15 LF155, LF156, LF256, LF257 LF355, LF356, LF357 SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 www.ti.com 7.3 Feature Description 7.3.1 Large Differential Input Voltage These are operational amplifiers with JFET input devices. 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. 7.3.2 Large Common-Mode Input Voltage These amplifiers will operate with the common-mode input voltage equal to the positive supply. In fact, the common-mode voltage can exceed the positive supply by approximately 100 mV independent of supply voltage and over the full operating temperature range. The positive supply can therefore be used as a reference on an input as, for example, in a supply current monitor and/or limiter. 7.4 Device Functional Modes The LFx5x has a single functional mode and operates according to the conditions listed in the Recommended Operating Conditions. 16 Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 LF155, LF156, LF256, LF257 LF355, LF356, LF357 www.ti.com SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 8 Application and Implementation NOTE Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality. 8.1 Application Information These are op amps with JFET input devices. 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 will be forced to a high state. These amplifiers will operate with the common-mode input voltage equal to the positive supply. In fact, the common-mode voltage can exceed the positive supply by approximately 100 mV independent of supply voltage and over the full operating temperature range. The positive supply can therefore be used as a reference on an input as, for example, in a supply current monitor and/or limiter. 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. All of the bias currents in these amplifiers are set by FET current sources. The drain currents for the amplifiers are therefore essentially independent of supply voltage. 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 six 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. Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 17 LF155, LF156, LF256, LF257 LF355, LF356, LF357 SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 www.ti.com 8.2 Typical Application Figure 35. Settling Time Test Circuit 8.2.1 Design Requirements Settling time is tested with the LF35x connected as unity gain inverter and LF357 connected for AV = −5 8.2.2 Detailed Design Procedure Connect the circuit components as shown in Figure 35. In particular, use FET to isolate the probe capacitance. Apply a 10-V step function to the input. Use an oscilloscope to probe the circuit as shown in Figure 35. 18 Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 LF155, LF156, LF256, LF257 LF355, LF356, LF357 www.ti.com SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 Typical Application (continued) 8.2.3 Application Curves Large Signal Inverter Output, VOUT (from Settling Time Circuit) Figure 36. LF355 Figure 37. LF356 Figure 38. LF357 Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 19 LF155, LF156, LF256, LF257 LF355, LF356, LF357 SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 www.ti.com 8.3 System Examples Figure 39. Low Drift Adjustable Voltage Reference • • • • • 20 ΔVOUT / ΔT = ±0.002%/°C All resistors and potentiometers should be wire-wound P1: drift adjust P2: VOUT adjust Use LF155 for – Low IB – Low drift – Low supply current Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 LF155, LF156, LF256, LF257 LF355, LF356, LF357 www.ti.com SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 System Examples (continued) Figure 40. Fast Logarithmic Converter • • • • • Dynamic range: 100 μA ≤ Ii ≤ 1 mA (5 decades), |VO| = 1 V/decade Transient response: 3 μs for ΔIi = 1 decade C1, C2, R2, R3: added dynamic compensation VOS adjust the LF156 to minimize quiescent error RT: Tel Labs type Q81 + 0.3%/°C (1) Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 21 LF155, LF156, LF256, LF257 LF355, LF356, LF357 SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 www.ti.com System Examples (continued) Figure 41. Precision Current Monitor • • • 22 VO = 5 R1/R2 (V/mA of IS) R1, R2, R3: 0.1% resistors Use LF155 for – Common-mode range to supply range – Low IB – Low VOS – Low Supply Current Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 LF155, LF156, LF256, LF257 LF355, LF356, LF357 www.ti.com SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 System Examples (continued) Figure 42. 8-Bit D/A Converter With Symmetrical Offset Binary Operation • • R1, R2 should be matched within ±0.05% Full-scale response time: 3 μs Table 1. Bit Illustration of the 8-Bit D/A Converter EO B1 B2 B3 B4 B5 B6 B7 B8 COMMENTS +9.920 1 1 1 1 1 1 1 1 Positive Full-Scale +0.040 1 0 0 0 0 0 0 0 (+) Zero-Scale −0.040 0 1 1 1 1 1 1 1 (−) Zero-Scale −9.920 0 0 0 0 0 0 0 0 Negative Full-Scale Figure 43. Wide BW Low Noise, Low Drift Amplifier (2) Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 23 LF155, LF156, LF256, LF257 LF355, LF356, LF357 SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 www.ti.com Parasitic input capacitance C1 ≃ (3 pF for LF155, LF156 and LF357 plus any additional layout capacitance) interacts with feedback elements and creates undesirable high frequency pole. To compensate add C2 such that: R2 C2 ≃ R1 C1. Figure 44. Boosting the LF156 With a Current Amplifier • IOUT(MAX) ≃ 150 mA (will drive RL ≥ 100 Ω) (3) • No additional phase shift added by the current amplifier Figure 45. Decades VCO 24 Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 LF155, LF156, LF256, LF257 LF355, LF356, LF357 www.ti.com SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 R1, R4 matched. Linearity 0.1% over 2 decades. (4) Figure 46. Isolating Large Capacitive Loads • • • Overshoot 6% ts 10 μs When driving large CL, the VOUT slew rate determined by CL and IOUT(MAX): (5) Figure 47. Low Drift Peak Detector • • • • By adding D1 and Rf, VD1 = 0 during hold mode. Leakage of D2 provided by feedback path through Rf. Leakage of circuit is essentially Ib (LF155, LF156) plus capacitor leakage of Cp. Diode D3 clamps VOUT (A1) to VIN − VD3 to improve speed and to limit reverse bias of D2. Maximum input frequency should be 100 Use LF155 for – Low IB – Low supply current Figure 55. VOS Adjustment • • • • VOS is adjusted with a 25-k potentiometer The potentiometer wiper is connected to V+ For potentiometers with temperature coefficient of 100 ppm/°C or less the additional drift with adjust is ≈ 0.5 μV/°C/mV of adjustment Typical overall drift: 5 μV/°C ±(0.5 μV/°C/mV of adj.) Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 31 LF155, LF156, LF256, LF257 LF355, LF356, LF357 SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 www.ti.com Figure 56. Driving Capacitive Loads • • • * LF15x R = 5k, LF357 R = 1.25 k Due to a unique output stage design, these amplifiers have the ability to drive large capacitive loads and still maintain stability. CL(MAX) ≃ 0.01 μF. Overshoot ≤ 20%, Settling time (ts) ≃ 5 μs Figure 57. LF357 - A Large Power BW Amplifier For distortion ≤ 1% and a 20 Vp-p VOUT swing, power bandwidth is: 500 kHz. 32 Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 LF155, LF156, LF256, LF257 LF355, LF356, LF357 www.ti.com SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 9 Power Supply Recommendations See the Recommended Operating Conditions for the minimum and maximum values for the supply input voltage and operating junction temperature. 10 Layout 10.1 Layout Guidelines 10.1.1 Printed-Circuit-Board Layout For High-Impedance Work It is generally recognized that any circuit which must operate with less than 1000 pA of leakage current requires special layout of the PCB. When one wishes to take advantage of the low input bias current of the LFx5x, typically less than 30 pA, it is essential to have an excellent layout. Fortunately, the techniques of obtaining low leakages are quite simple. First, the user must not ignore the surface leakage of the PCB, even though it may sometimes appear acceptably low, because under conditions of high humidity or dust or contamination, the surface leakage will be appreciable. To minimize the effect of any surface leakage, lay out a ring of foil completely surrounding the inputs of the LFx5x and the terminals of capacitors, diodes, conductors, resistors, relay terminals, and so forth, connected to the inputs of the op amp, as in Figure 62. To have a significant effect, guard rings must be placed on both the top and bottom of the PCB. This PC foil must then be connected to a voltage that is at the same voltage as the amplifier inputs, because no leakage current can flow between two points at the same potential. For example, a PCB trace-to-pad resistance of 10 TΩ, which is normally considered a very large resistance, could leak 5 pA if the trace were a 5-V bus adjacent to the pad of the input. If a guard ring is used and held close to the potential of the amplifier inputs, it will significantly reduce this leakage current. Figure 58. Inverting Amplifier Figure 59. Noninverting Amplifier Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 33 LF155, LF156, LF256, LF257 LF355, LF356, LF357 SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 www.ti.com Layout Guidelines (continued) Figure 60. Typical Connections Of Guard Rings The designer should be aware that when it is inappropriate to lay out a PCB for the sake of just a few circuits, there is another technique which is even better than a guard ring on a PCB: Do not insert the input pin of the amplifier into the board at all, but bend it up in the air and use only air as an insulator. Air is an excellent insulator. In this case you may have to forego some of the advantages of PCB construction, but the advantages are sometimes well worth the effort of using point-to-point up-in-the-air wiring. See Figure 61. (Input pins are lifted out of PCB and soldered directly to components. All other pins connected to PCB). Figure 61. Air Wiring Another potential source of leakage that might be overlooked is the device package. When the LFx5x is manufactured, the device is always handled with conductive finger cots. This is to assure that salts and skin oils do not cause leakage paths on the surface of the package. We recommend that these same precautions be adhered to, during all phases of inspection, test and assembly. 10.2 Layout Example Figure 62. Examples Of Guard Ring In PCB Layout 34 Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 LF155, LF156, LF256, LF257 LF355, LF356, LF357 www.ti.com SNOSBH0D – MAY 2000 – REVISED NOVEMBER 2015 11 Device and Documentation Support 11.1 Related Links The table below lists quick access links. Categories include technical documents, support and community resources, tools and software, and quick access to sample or buy. Table 2. Related Links PARTS PRODUCT FOLDER SAMPLE & BUY TECHNICAL DOCUMENTS TOOLS & SOFTWARE SUPPORT & COMMUNITY LF156 Click here Click here Click here Click here Click here LF256 Click here Click here Click here Click here Click here LF356 Click here Click here Click here Click here Click here 11.2 Community Resources The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of Use. TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help solve problems with fellow engineers. Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and contact information for technical support. 11.3 Trademarks BI-FET, E2E are trademarks of Texas Instruments. All other trademarks are the property of their respective owners. 11.4 Electrostatic Discharge Caution These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. 11.5 Glossary SLYZ022 — TI Glossary. This glossary lists and explains terms, acronyms, and definitions. 12 Mechanical, Packaging, and Orderable Information The following pages include mechanical, packaging, and orderable information. This information is the most current data available for the designated devices. This data is subject to change without notice and revision of this document. For browser-based versions of this data sheet, refer to the left-hand navigation. Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated LF156 LF256 LF356 35 PACKAGE OPTION ADDENDUM www.ti.com 10-Feb-2020 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish MSL Peak Temp (2) (6) (3) Op Temp (°C) Device Marking (4/5) LF156 MD8 ACTIVE DIESALE Y 0 204 Green (RoHS & no Sb/Br) Call TI Level-1-NA-UNLIM -55 to 125 LF156H ACTIVE TO-99 LMC 8 500 TBD Call TI Call TI -55 to 125 ( LF156H, LF156H) LF156H/NOPB ACTIVE TO-99 LMC 8 500 Green (RoHS & no Sb/Br) Call TI Level-1-NA-UNLIM -55 to 125 ( LF156H, LF156H) LF256H ACTIVE TO-99 LMC 8 500 TBD Call TI Call TI -25 to 85 ( LF256H, LF256H) LF256H/NOPB ACTIVE TO-99 LMC 8 500 Green (RoHS & no Sb/Br) Call TI Level-1-NA-UNLIM -25 to 85 ( LF256H, LF256H) LF356M NRND SOIC D 8 95 TBD Call TI Call TI 0 to 70 LF356 M LF356M/NOPB ACTIVE SOIC D 8 95 Green (RoHS & no Sb/Br) SN Level-1-260C-UNLIM 0 to 70 LF356 M LF356MX/NOPB ACTIVE SOIC D 8 2500 Green (RoHS & no Sb/Br) SN Level-1-260C-UNLIM 0 to 70 LF356 M LF356N/NOPB ACTIVE PDIP P 8 40 Green (RoHS & no Sb/Br) Call TI | SN Level-1-NA-UNLIM 0 to 70 LF 356N (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may reference these types of products as "Pb-Free". RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption. Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of