LMH6628MA

LMH6628 Dual Wideband, Low Noise, Voltage Feedback Op Amp January 2003 LMH6628 Dual Wideband, Low Noise, Voltage Feedback Op Amp General Description The National LMH6628 is a high speed dual op amp that offers a traditional voltage feedback topology featuring unity gain stability and slew enhanced circuitry. The LMH6628’s low noise and very low harmonic distortion combine to form a wide dynamic range op amp that operates from a single (5V to 12V) or dual ( ± 5V) power supply. Each of the LMH6628’s closely matched channels provides a 300MHz unity gain bandwidth and low input voltage noise ). Low 2nd/3rd harmonic distortion (−65/ density (2nV/ −74dBc at 10MHz) make the LMH6628 a perfect wide dynamic range amplifier for matched I/Q channels. With its fast and accurate settling (12ns to 0.1%), the LMH6628 is also an excellent choice for wide dynamic range, anti-aliasing filters to buffer the inputs of hi resolution analog-to-digital converters. Combining the LMH6628’s two tightly matched amplifiers in a single 8-pin SOIC package reduces cost and board space for many composite amplifier applications such as active filters, differential line drivers/ receivers, fast peak detectors and instrumentation amplifiers. The LMH6628 is fabricated using National’s VIP10™ complimentary bipolar process. To reduce design times and assist in board layout, the LMH6628 is supported by an evaluation board (CLC730036). Features n n n n n n n Wide unity gain bandwidth: 300MHz Low noise: 2nV/ Low Distortion: −65/−74dBc (10MHz) Settling time: 12ns to 0.1% Wide supply voltage range: ± 2.5V to ± 6V High output current: ± 85mA Improved replacement for CLC428 Applications n n n n n n High speed dual op amp Low noise integrators Low noise active filters Driver/receiver for transmission systems High speed detectors I/Q channel amplifiers Connection Diagram 8-Pin SOIC Inverting Frequency Response 20038535 Top View 20038515 © 2003 National Semiconductor Corporation DS200385 www.national.com LMH6628 Absolute Maximum Ratings (Note 1) Maximum Junction Temperature Storage Temperature Range Lead Temperature (soldering 10 sec) +150˚C −65˚C to +150˚C +300˚C If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. ESD Tolerance (Note 4) Human Body Model Machine Model Supply Voltage Short Circuit Current Common-Mode Input Voltage Differential Input Voltage 2kV 200V 13.5 (Note 3) V + - V− V + - V− Operating Ratings (Note 1) Thermal Resistance (Note 5) Package SOIC Temperature Range Nominal Supply Voltage (θJC) 65˚C/W (θJA) 145˚C/W −40˚C to +85˚C ± 2.5V to ± 6V Electrical Characteristics (Note 2) VCC = ± 5V, AV = +2V/V, RF = 100Ω, RG = 100Ω, RL = 100Ω; unless otherwise specified. Boldface limits apply at the temperature extremes. Symbol GB SSBW SSBW GFL GFP GFR LPD TR TS OS SR HD2 HD3 VN IN XTLKA GOL VIO DVIO IBN DIBN IOS IOSD PSRR CMRR ICC Parameter Gain Bandwidth Product -3dB Bandwidth, AV = +1 -3dB Bandwidth, AV = +2 Gain Flatness Peaking Rolloff Linear Phase Deviation Rise and Fall Time Settling Time Overshoot Slew Rate 2nd Harmonic Distortion 3rd Harmonic Distortion Equivalent Input Noise Voltage Current Crosstalk Open-Loop Gain Input Offset Voltage Average Drift Input Bias Current Average Drift Input Offset Current Average Drift Power Supply Rejection Ratio Common-Mode Rejection Ratio Supply Current Per Channel, RL = ∞ 60 46 57 54 7.5 7.0 1MHz to 100MHz 1MHz to 100MHz Input Referred, 10MHz 56 53 2 2 −62 63 nV/ pA/ dB dB Conditions VO < 0.5VPP VO < 0.5VPP VO < 0.5VPP VO < 0.5VPP DC to 200MHz DC to 20MHz DC to 20MHz 1V Step 2V Step to 0.1% 1V Step 4V Step 1VPP, 10MHz 1VPP, 10MHz 300 0.0 .1 .1 4 12 1 550 −65 −74 dB dB deg ns ns % V/µs dBc dBc 180 Min Typ 200 300 100 Max Units MHz MHz MHz Frequency Domain Response Time Domain Response Distortion And Noise Response Static, DC Performance ± .5 5 ±2 ± 2.6 ± 20 ± 30 ±6 mV µV/˚C µA nA/˚C µA nA/˚C dB dB ± .7 150 0.3 5 70 62 9 12 12.5 mA www.national.com 2 LMH6628 Electrical Characteristics (Note 2) Symbol RIN CIN ROUT VO VOL CMIR IO Input Voltage Range Output Current Parameter Input Resistance Input Capacitance Output Resistance Output Voltage Range (Continued) VCC = ± 5V, AV = +2V/V, RF = 100Ω, RG = 100Ω, RL = 100Ω; unless otherwise specified. Boldface limits apply at the temperature extremes. Conditions Common-Mode Differential-Mode Common-Mode Differential-Mode Closed-Loop RL = ∞ RL = 100Ω Common- Mode Min Typ 500 200 1.5 1.5 .1 Max Units kΩ kΩ pF pF Ω V V V mA Miscellaneous Performance ± 3.2 ± 3.1 ± 50 ± 3.8 ± 3.5 ± 3.7 ± 85 Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but specific performance is not guaranteed. For guaranteed specifications, see the Electrical Characteristics tables. Note 2: Electrical Table values apply only for factory testing conditions at the temperature indicated. Factory testing conditions result in very limited self-heating of the device such that TJ = TA. No guarantee of parametric performance is indicated in the electrical tables under conditions of internal self heating where TJ > TA. See Note 6 for information on temperature de-rating of this device." Min/Max ratings are based on product characterization and simulation. Individual parameters are tested as noted. Note 3: Output is short circuit protected to ground, however maximum reliability is obtained if output current does not exceed 160mA. Note 4: Human body model, 1.5kΩ in series with 100pF. Machine model, 0Ω In series with 200pF. Note 5: The maximum power dissipation is a function of TJ(MAX), θJA and TA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(MAX)-TA)/ θJA. All numbers apply for packages soldered directly onto a PC board. Ordering Information Package 8-pin SOIC Part Number LMH6628MA LMH6628MAX Package Marking LMH6628MA Transport Media Rails 2.5k Units Tape and Reel NSC Drawing M08A 3 www.national.com LMH6628 Typical Performance Characteristics less specified) Non-Inverting Frequency Response (TA = +25˚, AV = +2, VCC = ± 5V, Rf =100Ω, RL = 100Ω, unInverting Frequency Response 20038513 20038515 Frequency Response vs. Load Resistance Frequency Response vs. Output Amplitude 20038525 20038510 Frequency Response vs. Capacitive Load Gain Flatness & Linear Phase 20038516 20038524 www.national.com 4 LMH6628 Typical Performance Characteristics (TA = +25˚, AV = +2, VCC = ±5V, Rf =100Ω, RL = 100Ω, unless specified) (Continued) Channel Matching Channel to Channel Crosstalk 20038514 20038509 Pulse Response (VO = 2V) Pulse Response (VO = 100mV) 20038511 20038512 2nd Harmonic Distortion vs. Output Voltage 3rd Harmonic Distortion vs. Output Voltage 20038507 20038508 5 www.national.com LMH6628 Typical Performance Characteristics (TA = +25˚, AV = +2, VCC = ±5V, Rf =100Ω, RL = 100Ω, unless specified) (Continued) 2nd & 3rd Harmonic Distortion vs. Frequency PSRR and CMRR ( ± 5V) 20038517 20038522 PSRR and CMRR ( ± 2.5V) Closed Loop Output Resistance ( ± 2.5V) 20038523 20038518 Closed Loop Output Resistance ( ± 5V) Open Loop Gain & Phase ( ± 2.5V) 20038519 20038521 www.national.com 6 LMH6628 Typical Performance Characteristics (TA = +25˚, AV = +2, VCC = ±5V, Rf =100Ω, RL = 100Ω, unless specified) (Continued) Open Loop Gain & Phase ( ± 5V) Recommended RS vs. CL 20038520 20038526 DC Errors vs. Temperature Maximum VO vs. RL 20038546 20038545 2-Tone, 3rd Order Intermodulation Intercept Voltage & Current Noise vs. Frequency 20038544 20038547 7 www.national.com LMH6628 Typical Performance Characteristics (TA = +25˚, AV = +2, VCC = ±5V, Rf =100Ω, RL = 100Ω, unless specified) (Continued) Settling Time vs. Accuracy 20038548 Application Section LOW NOISE DESIGN Ultimate low noise performance from circuit designs using the LMH6628 requires the proper selection of external resistors. By selecting appropriate low valued resistors for RF and RG, amplifier circuits using the LMH6628 can achieve output noise that is approximately the equivalent voltage input multiplied by the desired gain (AV). noise of 2nV/ DC BIAS CURRENTS AND OFFSET VOLTAGES Cancellation of the output offset voltage due to input bias currents is possible with the LMH6628. This is done by making the resistance seen from the inverting and noninverting inputs equal. Once done, the residual output offset voltage will be the input offset voltage (VOS) multiplied by the desired gain (AV). National Application Note OA-7 offers several solutions to further reduce the output offset. OUTPUT AND SUPPLY CONSIDERATIONS With ± 5V supplies, the LMH6628 is capable of a typical output swing of ± 3.8V under a no-load condition. Additional output swing is possible with slightly higher supply voltages. For loads of less than 50Ω, the output swing will be limited by the LMH6628’s output current capability, typically 85mA. Output settling time when driving capacitive loads can be improved by the use of a series output resistor. See the plot labeled "RS vs. CL" in the Typical Performance section. LAYOUT Proper power supply bypassing is critical to insure good high frequency performance and low noise. De-coupling capacitors of 0.1µF should be placed as close as possible to the power supply pins. The use of surface mounted capacitors is recommended due to their low series inductance. A good high frequency layout will keep power supply and ground traces away from the inverting input and output pins. Parasitic capacitance from these nodes to ground causes frequency response peaking and possible circuit oscillation. See OA-15 for more information. National suggests the 730036 (SOIC) dual op amp evaluation board as a guide for high frequency layout and as an aid in device evaluation. ANALOG DELAY CIRCUIT (ALL-PASS NETWORK) The circuit in Figure 1 implements an all-pass network using the LMH6628. A wide bandwidth buffer (LM7121) drives the circuit and provides a high input impedance for the source. As shown in Figure 2, the circuit provides a 13.1ns delay (with R = 40.2Ω, C = 47pF). RF and RG should be of equal and low value for parasitic insensitive operation. 20038501 FIGURE 1. 20038502 FIGURE 2. Delay Circuit Response to 0.5V Pulse www.national.com 8 LMH6628 Application Section (Continued) The circuit gain is +1 and the delay is determined by the following equations. (1) Td = 1 dφ 360 df ; (2) where Td is the delay of the op amp at AV = +1. The LMH6628 provides a typical delay of 2.8ns at its −3dB point. FULL DUPLEX DIGITAL OR ANALOG TRANSMISSION Simultaneous transmission and reception of analog or digital signals over a single coaxial cable or twisted-pair line can reduce cabling requirements. The LMH6628’s wide bandwidth and high common-mode rejection in a differential amplifier configuration allows full duplex transmission of video, telephone, control and audio signals. In the circuit shown in Figure 3, one of the LMH6628’s amps is used as a "driver" and the other as a difference "receiver" amplifier. The output impedance of the "driver" is essentially zero. The two R’s are chosen to match the characteristic impedance of the transmission line. The "driver" op amp gain can be selected for unity or greater. Receiver amplifier A2 (B2) is connected across R and forms differential amplifier for the signals transmitted by driver A2 (B2). If RF equals RG, receiver A2 (B1) will then reject the signals from driver A1 (B1) and pass the signals from driver B1 (A1). FIGURE 4. POSITIVE PEAK DETECTOR 20038531 The LMH6628’s dual amplifiers can be used to implement a unity-gain peak detector circuit as shown in Figure 5. 20038505 FIGURE 5. The acquisition speed of this circuit is limited by the dynamic resistance of the diode when charging Chold. A plot of the circuit’s performance is shown in Figure 6 with a 1MHz sinusoidal input. 20038503 FIGURE 3. The output of the receiver amplifier will be: (3) Care must be given to layout and component placement to maintain a high frequency common-mode rejection. The plot of Figure 4 shows the simultaneous reception of signals transmitted at 1MHz and 10MHz. 9 www.national.com LMH6628 Application Section (Continued) (4) To build a boost circuit, use the design equations Eq. 6 and Eq. 7. (5) (6) 20038537 FIGURE 6. A current source, built around Q1, provides the necessary bias current for the second amplifier and prevents saturation when power is applied. The resistor, R, closes the loop while diode D2 prevents negative saturation when VIN is less than VC. A MOS-type switch (not shown) can be used to reset the capacitor’s voltage. The maximum speed of detection is limited by the delay of the op amps and the diodes. The use of Schottky diodes will provide faster response. ADJUSTABLE OR BANDPASS EQUALIZER A "boost" equalizer can be made with the LMH6628 by summing a bandpass response with the input signal, as shown in Figure 7. Select R2 and C using Eq. 6. Use reasonable values for high frequency circuits - R2 between 10Ω and 5kΩ, C between 10pF and 2000pF. Use Eq. 7 to determine the parallel combination of Ra and Rb. Select Ra and Rb by either the 10Ω to 5kΩ criteria or by other requirements based on the impedance Vin is capable of driving. Finish the design by determining the value of K from Eq. 8. (7) Figure 8 shows an example of the response of the circuit of Figure 9, where fo is 2.3MHz. The component values are as follows: Ra =2.1kΩ, Rb = 68.5Ω, R2 = 4.22kΩ, R = 500Ω, KR = 50Ω, C = 120pF. 20038506 20038543 FIGURE 7. The overall transfer function is shown in Eq. 5. FIGURE 8. www.national.com 10 LMH6628 Dual Wideband, Low Noise, Voltage Feedback Op Amp Physical Dimensions unless otherwise noted inches (millimeters) 8-Pin SOIC NS Package Number M08A 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 AND GENERAL COUNSEL 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. 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National Semiconductor Asia Pacific Customer Support Center Fax: 65-6250 4466 Email: ap.support@nsc.com Tel: 65-6254 4466 National Semiconductor Japan Customer Support Center Fax: 81-3-5639-7507 Email: nsj.crc@jksmtp.nsc.com Tel: 81-3-5639-7560 National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.