LME49871 High Performance, High Fidelity Current Feedback Audio Operational Amplifier General Description Key Specifications The LME49871 is an ultra-low distortion, low noise, ultra high slew rate current feedback operational amplifier optimized and fully specified for high performance, high fidelity applications. Combining advanced leading-edge process technology with state-of-the-art circuit design, the LME49871 current feedback operational amplifier delivers superior signal amplification for outstanding performance. Operating on a wide supply range of ±5V to ±22V, the LME49871 combines extremely low voltage noise density (1.9nV/√Hz) with very low THD+N (0.00012%) to easily satisfy the most demanding applications. To ensure that the most challenging loads are driven without compromise, the LME49871 has a high slew rate of ±1900V/μs and an output current capability of ±100mA. Further, dynamic range is maximized by an output stage that drives 150Ω loads to within 2.9V of either power supply voltage. The LME49871 's outstanding CMRR (88dB), PSRR (102dB), and VOS (0.05mV) give the amplifier excellent operational amplifier DC performance. The LME49871 is available in an 8–lead narrow body SOIC. Demonstration boards are available. ■ Power Supply Voltage Range ±5V to ±22V ■ THD+N (AV = 1, RL = 100Ω, VOUT = 2VP-P, f = 1kHz) 0.00021% (typ) ■ THD+N (AV = 1, RL = 600Ω, VOUT = 1.4VRMS, f = 1kHz) 0.00012% (typ) ■ Input Noise Density 1.9nV/√Hz (typ) ■ Slew Rate ±1900V/μs (typ) ■ Bandwidth (AV = 1, RL= 2kΩ, RF = 800Ω) ■ Input Bias Current ■ Input Offset Voltage 213MHz (typ) 1.8μA (typ) 0.05mV (typ) ■ PSRR 102dB (typ) ■ CMRR 90dB (typ) Features ■ ■ ■ ■ Easily drives 150Ω loads Optimized for superior audio signal fidelity Output short circuit protection SOIC package Applications ■ ■ ■ ■ ■ ■ ■ ■ ■ © 2008 National Semiconductor Corporation 300426 Ultra high quality audio amplification High fidelity preamplifiers High fidelity multimedia State of the art phono pre amps High performance professional audio High fidelity equalization and crossover networks High performance line drivers High performance line receivers High fidelity active filters www.national.com LME49871 High Performance, High Fidelity Current Feedback Audio Operational Amplifier April 28, 2008 LME49871 Connection Diagrams SOIC Package 30042601 Order Number LME49871MA See NS Package Number M08A LME49871MA Top Mark 30042602 N = National Logo Z = Assembly plant code X = 1 Digit date code TT = Die traceability L49871 = LME49871 MA = Package code www.national.com 2 If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Power Supply Voltage (VS = V+ - V-) Storage Temperature Input Voltage 46V −65°C to 150°C Output Short Circuit (Note 3) Power Dissipation 2000V 200V 100V 150°C θJA (MA) Temperature Range (V-) - 0.7V to (V+) + 0.7V Continuous Internally Limited 145°C/W TMIN ≤ TA ≤ TMAX Supply Voltage Range –40°C ≤ TA ≤ 85°C ±5.0V ≤ VS ≤ ±22V Electrical Characteristics (Notes 1, 2) The following specifications apply for ±22V, RL = 2kΩ, RSOURCE = 10Ω, fIN = 1kHz, and TA = 25°C, unless otherwise specified. LME49871 Symbol Parameter Conditions Typical Limit (Note 6) (Note 7) Units (Limits) AV = 1, f = 1kHz, RF = 1.2kΩ THD+N Total Harmonic Distortion + Noise RL = 100Ω, VOUT = 3VRMS RL = 600Ω, VOUT = 1.4VRMS 0.00021 0.00012 % % 0.00009 % 213 MHz ±1900 V/μs IMD Intermodulation Distortion AV = 1, VIN = 3VRMS Two-tone, 60Hz & 7kHz 4:1 BW Bandwidth AV = –1, RF = 800Ω SR Slew Rate VOUT = 20VP-P, AV = –5 FPBW Full Power Bandwidth VOUT = 20VP-P, –3dB referenced to output magnitude at f = 1kHz, AV = 1 30 MHz ts Settling Time AV = –1, 10V step, 0.1% error range 50 ns Equivalent Input Noise Voltage fBW = 20Hz to 20kHz 0.26 0.6 μVRMS Equivalent Input Noise Density f = 1kHz f = 10Hz 1.9 11.5 4.0 nV/√Hz in Current Noise Density f = 1kHz f = 10Hz 16 160 VOS Input Offset Voltage en ±0.05 Average Input Offset Voltage Drift vs ΔVOS/ΔTemp –40°C ≤ TA ≤ 85°C Temperature PSRR Average Input Offset Voltage Shift vs VS = ±22V, ΔVS = 30V (Note 8) Power Supply Voltage IB Input Bias Current ΔIOS/ΔTemp IOS (max) pA/√Hz pA/√Hz ±1.0 mV (max) μV/°C 0.29 102 100 dB (min) VCM = 0V 1.8 6 μA (max) Input Bias Current Drift vs Temperature –40°C ≤ TA ≤ 85°C Inverting input Non-inverting input 4.5 4.7 Input Offset Current VCM = 0V 1.3 5 μA (max) ±20.5 (V+) – 1.0 (V-) + 1.0 V (min) V (min) 86 dB (min) VIN-CM Common-Mode Input Voltage Range VS = ±22V CMRR Common-Mode Rejection ZIN (max) nA/°C nA/°C –10V ≤ VCM ≤ 10V 90 Non-inverting-input Input Impedance –10V ≤ VCM ≤ 10V 1.2 MΩ –10V ≤ VCM ≤ 10V 58 Ω Inverting-input Input Impedance VOUT = ±10V ZT Transimpedance RL = 200Ω 4.2 4.7 RL = ∞ 3 2.0 2.65 MΩ (min) MΩ (min) www.national.com LME49871 ESD Rating (Note 4) ESD Rating (Note 5) Pins 1, 4, 7 and 8 Pins 2, 3, 5 and 6 Junction Temperature Thermal Resistance Absolute Maximum Ratings (Notes 1, 2) LME49871 LME49871 Symbol VOUTMAX Maximum Output Voltage Swing IOUT Output Current IOUT-CC Instantaneous Short Circuit Current Units (Limits) Typical Limit (Note 6) (Note 7) RL = 150Ω ±18.6 ±17.6 V (min) RL = 600Ω ±19.4 ±18.4 V (min) RL = 150Ω, VS = ±22V ±100 ±93 mA (min) Parameter Conditions ±140 ROUT Output Resistance fIN = 5MHz Open-Loop IS Total Quiescent Current IOUT = 0mA 10 8.3 mA 9.5 Ω mA (max) Note 1: “Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur, including inoperability and degradation of device reliability and/or performance. Functional operation of the device and/or non-degradation at the Absolute Maximum Ratings or other conditions beyond those indicated in the Recommended Operating Conditions is not implied. TheRecommended Operating Conditions indicate conditions at which the device is functional and the device should not be operated beyond such conditions. All voltages are measured with respect to the ground pin, unless otherwise specified. Note 2: The Electrical Characteristics tables list guaranteed specifications under the listed Recommended Operating Conditions except as otherwise modified or specified by the Electrical Characteristics Conditions and/or Notes. Typical specifications are estimations only and are not guaranteed. Note 3: Amplifier output connected to GND, any number of amplifiers within a package. Note 4: Human body model, applicable std. JESD22-A114C. Note 5: Machine model, applicable std. JESD22-A115-A. Note 6: Typical values represent most likely parametric norms at TA = +25ºC, and at the Recommended Operation Conditions at the time of product characterization and are not guaranteed. Note 7: Datasheet min/max specification limits are guaranteed by test or statistical analysis. Note 8: PSRR is measured as follows: VOS is measured at two supply voltages, ±7V and ±22V. PSRR = | 20log(ΔVOS/ΔVS) |. www.national.com 4 FFT of 1kHz Sinewave, 0dBr Input Magnitude VOUT = 3VRMS, RL = 1kΩ, VS = ±15V, AV = 1 FFT of 1kHz Sinewave, 0dBr Input Magnitude VOUT = 3VRMS, RL = 100Ω, VS = ±15V, AV = 1 30042619 30042620 FFT of 1kHz Sinewave, 0dBr Input Magnitude VOUT = 3VRMS, RL = 600Ω, VS = ±15V, AV = 1 FFT of 1kHz Sinewave, 0dBr Input Magnitude VOUT = 1.4VRMS, RL = 1kΩ, VS = ±15V, AV = 1 30042621 30042616 FFT of 1kHz Sinewave, 0dBr Input Magnitude VOUT = 1.4VRMS, RL = 100Ω, VS = ±15V, AV = 1 FFT of 1kHz Sinewave, 0dBr Input Magnitude VOUT = 1.4VRMS, RL = 600Ω, VS = ±15V, AV = 1 30042617 30042618 5 www.national.com LME49871 Typical Performance Characteristics LME49871 FFT of 1kHz Sinewave, 0dBr Input Magnitude VOUT = 3VRMS, RL = 1kΩ, VS = ±22V, AV = 1 FFT of 1kHz Sinewave, 0dBr Input Magnitude VOUT = 3VRMS, RL = 100Ω, VS = ±22V, AV = 1 30042681 30042682 FFT of 1kHz Sinewave, 0dBr Input Magnitude VOUT = 3VRMS, RL = 600Ω, VS = ±22V, AV = 1 FFT of 1kHz Sinewave, 0dBr Input Magnitude VOUT = 1.4VRMS, RL = 1kΩ, VS = ±22V, AV = 1 30042680 30042677 FFT of 1kHz Sinewave, 0dBr Input Magnitude VOUT = 1.4VRMS, RL = 100Ω, VS = ±22V, AV = 1 FFT of 1kHz Sinewave, 0dBr Input Magnitude VOUT = 1.4VRMS, RL = 600Ω, VS = ±22V, AV = 1 30042678 www.national.com 30042679 6 LME49871 Output Voltage vs Supply Voltage AV = 1, RL = 600Ω, 1% THD+N Output Voltage vs Supply Voltage AV = 1, RL = open, 1% THD+N 30042687 30042688 Supply Current (ICC) vs Power Supply RL = open Gain vs Frequency VS = ±15V, G = –1 30042604 30042689 Gain vs Frequency VS = ±15V, G = –2 Gain vs Frequency VS = ±15V, G = –5 30042605 30042606 7 www.national.com LME49871 Gain vs Frequency VS = ±15V, G = –10 Gain vs Frequency VS = ±15V, RF = 800Ω 30042607 30042608 Gain vs Frequency VS = ±15V, RF = 1.2kΩ Gain vs Frequency VS = ±15V, RF = 2kΩ 30042610 30042609 Gain vs Frequency VS = ±15V, RF = 3kΩ Gain vs Frequency VS = ±22V, RF = 1.2kΩ 30042611 30042683 www.national.com 8 LME49871 Gain vs Frequency VS = ±22V, RF = 2kΩ Gain vs Frequency VS = ±22V, RF = 3kΩ 30042685 30042684 Gain vs Frequency VS = ±22V, RF = 800Ω Gain vs Frequency VS = ±22V, AV = –1 30042671 30042686 Gain vs Frequency VS = ±22V, AV = –2 Gain vs Frequency VS = ±22V, AV = –5 30042673 30042675 9 www.national.com LME49871 Gain vs Frequency VS = ±22V, AV = –10 30042670 www.national.com 10 GENERAL AMPLIFIER FUNCTION oltage feedback amplifiers have a small-signal bandwidth that is a function of the closed-loop gain. Conversely, the LME49871 current feedback amplifier features a small-signal bandwidth that is relatively independent of the closed-loop gain. This is shown in Figure 1 where the LME49871’s gain is –1,–2, –5 and –10. Like all current feedback amplifiers, the LME49871’s closed-loop bandwidth is a function of the feedback resistance value. Therefore, Rs must be varied to select the desired closed-loop gain. DRIVING CAPACITIVE LOADS The LME49871 can drive significantly higher capacitive loads than many current feedback amplifiers. Although the LME49871 can directly drive as much as 100pF without oscillating, the resulting response will be a function of the feedback resistor value. POWER SUPPLY BYPASSING AND LAYOUT CONSIDERATIONS Properly placed and correctly valued supply bypassing is essential for optimized high-speed amplifier operation. The supply bypassing must maintain a wideband, low-impedance capacitive connection between the amplifier’s supply pin and ground. This helps preserve high speed signal and fast transient fidelity. The bypassing is easily accomplished using a parallel combination of a 10μF tantalum and a 0.1μF ceramic capacitors for each power supply pin. The bypass capacitors should be placed as close to the amplifier power supply pins as possible. CAPACITIVE FEEDBACK It is quite common to place a small lead-compensation capacitor in parallel with a voltage feedback amplifier’s feedback resistance, Rf. This compensation reduces the amplifier’s peaking in the frequency domain and damps the transient response. Whereas this yields the expected results when used with voltage feedback amplifiers, this technique must not be used with current feedback amplifiers. The dynamic impedance of capacitors in the feedback loop reduces the amplifier’s stability. Instead, reduced peaking in the frequency response and bandwidth limiting can be accomplished by adding an RC circuit to the amplifier’s input. FEEDBACK RESISTOR SELECTION (Rf) The value of the Rf, is also a dominant factor in compensating the LME49871. For general applications, the LME49871 will maintain specified performance with an 1.2kΩ feedback resistor. Although this value will provide good results for most applications, it may be advantageous to adjust this value slightly for best pulse response optimized for the desired bandwidth. In addition to reducing bandwidth, increasing the feedback resistor value also reduces overshoot in the time domain response. 300426p0 FIGURE 1. Bandwidth as a function of gain 11 www.national.com LME49871 SLEW RATE CONSIDERATIONS A current feedback amplifier’s slew rate characteristics are different than that of voltage feedback amplifiers. A voltage feedback amplifier’s slew rate limiting or non-linear amplifier behavior is dominated by the finite availability of the first stage tail current charging the second stage voltage amplifier’s compensation capacitor. Conversely, a current feedback amplifier’s slew rate is not constant. Transient current at the inverting input determines slew rate for both inverting and non-inverting gains. The non-inverting configuration slew rate is also determined by input stage limitations. Accordingly, variations of slew rates occur for different circuit topologies. Application Information LME49871 Revision History Rev Date 1.0 04/24/08 Initial release. 1.01 04/28/08 Changed the Limit values on VIN-CM from –2.0 and +2.0 to –1.0 and +1.0. www.national.com Description 12 LME49871 Physical Dimensions inches (millimeters) unless otherwise noted SOIC Package Order Number LME49871MA NS Package Number M08A 13 www.national.com LME49871 High Performance, High Fidelity Current Feedback Audio Operational Amplifier Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: Products Design Support Amplifiers www.national.com/amplifiers WEBENCH www.national.com/webench Audio www.national.com/audio Analog University www.national.com/AU Clock Conditioners www.national.com/timing App Notes www.national.com/appnotes Data Converters www.national.com/adc Distributors www.national.com/contacts Displays www.national.com/displays Green Compliance www.national.com/quality/green Ethernet www.national.com/ethernet Packaging www.national.com/packaging Interface www.national.com/interface Quality and Reliability www.national.com/quality LVDS www.national.com/lvds Reference Designs www.national.com/refdesigns Power Management www.national.com/power Feedback www.national.com/feedback Switching Regulators www.national.com/switchers LDOs www.national.com/ldo LED Lighting www.national.com/led PowerWise www.national.com/powerwise Serial Digital Interface (SDI) www.national.com/sdi Temperature Sensors www.national.com/tempsensors Wireless (PLL/VCO) www.national.com/wireless THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. 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