LMH6624/LMH6626 Single/Dual Ultra Low Noise Wideband Operational Amplifier General Description Features The LMH6624/LMH6626 offer wide bandwidth (1.5GHz for single, 1.3GHz for dual) with very low input noise (0.92nV/ , 2.3pA/ ) and ultra low dc errors (100µV VOS, ± 0.1µV/˚C drift) providing very precise operational amplifiers with wide dynamic range. This enables the user to achieve closed-loop gains of greater than 10, in both inverting and non-inverting configurations. The LMH6624 (single) and LMH6626’s (dual) traditional voltage feedback topology provide the following benefits: balanced inputs, low offset voltage and offset current, very low offset drift, 81dB open loop gain, 95dB common mode rejection ratio, and 88dB power supply rejection ratio. The LMH6624/LMH6626 operate from ± 2.5V to ± 6V in dual supply mode and from +5V to +12V in single supply configuration. LMH6624 is offered in SOT23-5 and SOIC-8 packages. The LMH6626 is offered in SOIC-8 and MSOP-8 packages. VS = ± 6V, TA = 25˚C, AV = 20, (Typical values unless specified) n Gain bandwidth (LMH6624) 1.5GHz n Input voltage noise 0.92nV/ n Input offset voltage (limit over temp) 700uV n Slew rate 350V/µs n Slew rate (AV = 10) 400V/µs n HD2 @ f = 10MHz, RL = 100Ω −63dBc n HD3 @ f = 10MHz, RL = 100Ω −80dBc ± 2.5V to ± 6V n Supply voltage range (dual supply) n Supply voltage range (single supply) +5V to +12V n Improved replacement for the CLC425 (LMH6624) n Stable for closed loop |AV| ≥ 10 Applications n n n n n n n Instrumentation sense amplifiers Ultrasound pre-amps Magnetic tape & disk pre-amps Wide band active filters Professional Audio Systems Opto-electronics Medical diagnostic systems Connection Diagrams 5-Pin SOT23 8−Pin SOIC 20058952 20058951 Top View Top View © 2003 National Semiconductor Corporation 8−Pin SOIC/MSOP DS200589 20058961 Top View www.national.com LMH6624/LMH6626 Single/Dual Ultra Low Noise Wideband Operational Amplifier May 2003 LMH6624/LMH6626 Absolute Maximum Ratings Wave Soldering (10 sec.) (Note 1) Storage Temperature Range If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Machine Model Operating Temperature Range (Note 3), (Note 4) 200V (Note 9) ± 1.2V Supply Voltage (V+ - V−) 13.2V Voltage at Input pins −40˚C to +125˚C Package Thermal Resistance (θJA)(Note 4) V+ +0.5V, V− −0.5V Soldering Information Infrared or Convection (20 sec.) +150˚C Operating Ratings (Note 1) 2000V (Note 2) VIN Differential −65˚C to +150˚C Junction Temperature (Note 3), (Note 4) ESD Tolerance Human Body Model 260˚C 235˚C SOIC-8 166˚C/W SOT23–5 265˚C/W MSOP-8 235˚C/W ± 2.5V Electrical Characteristics Unless otherwise specified, all limits guaranteed at TA = 25˚C, V+ = 2.5V, V− = −2.5V, VCM = 0V, AV = +20, RF = 500Ω, RL = 100Ω. Boldface limits apply at the temperature extremes. See (Note 12). Symbol Parameter Conditions Min (Note 6) Typ (Note 5) Max (Note 6) Units Dynamic Performance fCL SR −3dB BW Slew Rate(Note 8) VO = 400mVPP (LMH6624) 90 VO = 400mVPP (LMH6626) 80 VO = 2VPP, AV = +20 (LMH6624) 300 VO = 2VPP, AV = +20 (LMH6626) 290 VO = 2VPP, AV = +10 (LMH6624) 360 MHz V/µs VO = 2VPP, AV = +10 (LMH6626) 340 tr Rise Time VO = 400mV Step, 10% to 90% 4.1 ns tf Fall Time VO = 400mV Step, 10% to 90% 4.1 ns ts Settling Time 0.1% VO = 2VPP (Step) 20 ns Distortion and Noise Response en in HD2 HD3 Input Referred Voltage Noise Input Referred Current Noise 2nd Harmonic Distortion 3 rd Harmonic Distortion f = 1MHz (LMH6624) 0.92 f = 1MHz (LMH6626) 1.0 f = 1MHz (LMH6624) 2.3 f = 1MHz (LMH6626) 1.8 fC = 10MHz, VO = 1VPP, RL 100Ω −60 dBc fC = 10MHz, VO = 1VPP, RL 100Ω −76 dBc nV/ pA/ Input Characteristics VOS Input Offset Voltage Average Drift (Note 7) VCM = 0V IOS Input Offset Current VCM = 0V Average Drift (Note 7) VCM = 0V 2 Input Bias Current VCM = 0V 13 Average Drift (Note 7) VCM = 0V 12 nA/˚C Input Resistance (Note 10) Common Mode 6.6 MΩ Differential Mode 4.6 kΩ Common Mode 0.9 pF Differential Mode 2.0 IB RIN CIN CMRR Input Capacitance (Note 10) Common Mode Rejection Ratio www.national.com VCM = 0V −0.75 −0.95 −0.25 +0.75 +0.95 ± 0.25 −1.5 −2.0 −0.05 mV µV/˚C +1.5 +2.0 µA nA/˚C +20 +25 µA Input Referred, VCM = −0.5 to +1.9V VCM = −0.5 to +1.75V 2 87 85 90 dB (Continued) Unless otherwise specified, all limits guaranteed at TA = 25˚C, V+ = 2.5V, V− = −2.5V, VCM = 0V, AV = +20, RF = 500Ω, RL = 100Ω. Boldface limits apply at the temperature extremes. See (Note 12). Symbol Parameter Conditions Min (Note 6) Typ (Note 5) (LMH6624) RL = 100Ω, VO = −1V to +1V 75 70 79 (LMH6626) RL = 100Ω, VO = −1V to +1V 72 67 79 Max (Note 6) Units Transfer Characteristics AVOL Xt Large Signal Voltage Gain Crosstalk Rejection f = 1MHz (LMH6626) dB −75 dB Output Characteristics VO Output Swing ± 1.1 ± 1.0 ± 1.4 ± 1.25 RL = 100Ω No Load ± 1.5 RO Output Impedance f ≤ 100KHz ISC Output Short Circuit Current (LMH6624) Sourcing to Ground ∆VIN = 200mV (Note 3), (Note 11) 90 75 145 (LMH6624) Sinking to Ground ∆VIN = −200mV (Note 3), (Note 11) 90 75 145 (LMH6626) Sourcing to Ground ∆VIN = 200mV (Note 3),(Note 11) 60 50 120 (LMH6626) Sinking to Ground ∆VIN = −200mV (Note 3),(Note 11) 60 50 120 IOUT Output Current V ± 1.7 10 (LMH6624) Sourcing, VO = +0.8V Sinking, VO = −0.8V 100 (LMH6626) Sourcing, VO = +0.8V Sinking, VO = −0.8V 75 mΩ mA mA Power Supply PSRR Power Supply Rejection Ratio VS = ± 2.0V to ± 3.0V IS Supply Current (per channel) No Load 82 80 90 11.4 dB 16 18 mA ± 6V Electrical Characteristics Unless otherwise specified, all limits guaranteed at TA = 25˚C, V+ = 6V, V− = −6V, VCM = 0V, AV = +20, RF = 500Ω, RL = 100Ω. Boldface limits apply at the temperature extremes. See (Note 12). Symbol Parameter Conditions Min (Note 6) Typ (Note 5) Max (Note 6) Units Dynamic Performance fCL SR tr −3dB BW Slew Rate (Note 8) Rise Time VO = 400mVPP (LMH6624) 95 VO = 400mVPP (LMH6626) 85 VO = 2VPP, AV = +20 (LMH6624) 350 VO = 2VPP, AV = +20 (LMH6626) 320 VO = 2VPP, AV = +10 (LMH6624) 400 VO = 2VPP, AV = +10 (LMH6626) 360 VO = 400mV Step, 10% to 90% 3.7 3 MHz V/µs ns www.national.com LMH6624/LMH6626 ± 2.5V Electrical Characteristics LMH6624/LMH6626 ± 6V Electrical Characteristics (Continued) Unless otherwise specified, all limits guaranteed at TA = 25˚C, V+ = 6V, V− = −6V, VCM = 0V, AV = +20, RF = 500Ω, RL = 100Ω. Boldface limits apply at the temperature extremes. See (Note 12). Symbol Parameter Conditions Min (Note 6) Typ (Note 5) Max (Note 6) Units tf Fall Time VO = 400mV Step, 10% to 90% 3.7 ns ts Settling Time 0.1% VO = 2VPP (Step) 18 ns Distortion and Noise Response en in HD2 HD3 Input Referred Voltage Noise Input Referred Current Noise 2nd Harmonic Distortion 3 rd Harmonic Distortion f = 1MHz (LMH6624) 0.92 f = 1MHz (LMH6626) 1.0 f = 1MHz (LMH6624) 2.3 f = 1MHz (LMH6626) 1.8 fC = 10MHz, VO = 1VPP, RL 100Ω −63 dBc fC = 10MHz, VO = 1VPP, RL 100Ω −80 dBc nV/ pA/ Input Characteristics VOS IOS IB −0.5 −0.7 ± 0.10 Input Offset Voltage VCM = 0V +0.5 +0.7 Average Drift (Note 7) VCM = 0V Input Offset Current Average Drift (Note 7) (LMH6624) VCM = 0V −1.1 −2.5 0.05 1.1 2.5 (LMH6626) VCM = 0V −2.0 −2.5 0.1 2.0 2.5 ± 0.2 VCM = 0V 0.7 Input Bias Current VCM = 0V 13 mV µV/˚C µA nA/˚C +20 +25 µA Average Drift (Note 7) VCM = 0V 12 nA/˚C RIN Input Resistance (Note 10) Common Mode 6.6 MΩ Differential Mode 4.6 kΩ CIN Input Capacitance (Note 10) Common Mode 0.9 Differential Mode 2.0 CMRR Common Mode Rejection Ratio pF Input Referred, VCM = −4.5 to +5.25V VCM = −4.5 to +5.0V 90 87 95 (LMH6624) RL = 100Ω, VO = −3V to +3V 77 72 81 (LMH6626) RL = 100Ω, VO = −3V to +3V 74 70 80 dB Transfer Characteristics AVOL Xt Large Signal Voltage Gain Crosstalk Rejection f = 1MHz (LMH6626) −75 dB dB Output Characteristics VO Output Swing ± 4.4 ± 4.3 ± 4.8 ± 4.65 ± 4.3 ± 4.2 ± 4.8 ± 4.65 (LMH6624) RL = 100Ω (LMH6624) No Load (LMH6626) RL = 100Ω (LMH6626) No Load RO Output Impedance www.national.com f ≤ 100KHz ± 4.9 ± 5.2 ± 4.8 ± 5.2 10 4 V mΩ (Continued) Unless otherwise specified, all limits guaranteed at TA = 25˚C, V+ = 6V, V− = −6V, VCM = 0V, AV = +20, RF = 500Ω, RL = 100Ω. Boldface limits apply at the temperature extremes. See (Note 12). Symbol Parameter Output Short Circuit Current ISC IOUT Output Current Conditions Min (Note 6) Typ (Note 5) (LMH6624) Sourcing to Ground ∆VIN = 200mV (Note 3), (Note 11) 100 85 156 (LMH6624) Sinking to Ground ∆VIN = −200mV (Note 3), (Note 11) 100 85 156 (LMH6626) Sourcing to Ground ∆VIN = 200mV (Note 3), (Note 11) 65 55 120 (LMH6626) Sinking to Ground ∆VIN = −200mV (Note 3), (Note 11) 65 55 120 (LMH6624) Sourcing, VO = +4.3V Sinking, VO = −4.3V 100 (LMH6626) Sourcing, VO = +4.3V Sinking, VO = −4.3V 80 Max (Note 6) Units mA mA Power Supply PSRR Power Supply Rejection Ratio VS = ± 5.4V to ± 6.6V IS Supply Current (per channel) No Load 82 80 88 12 dB 16 18 mA 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 and the test conditions, see the Electrical Characteristics. Note 2: Human body model, 1.5kΩ in series with 100pF. Note 3: Applies to both single-supply and split-supply operation. Continuous short circuit operation at elevated ambient temperature can result in exceeding the maximum allowed junction temperature of 150˚C. Note 4: 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. Note 5: Typical Values represent the most likely parametric norm. Note 6: All limits are guaranteed by testing or statistical analysis. Note 7: Average drift is determined by dividing the change in parameter at temperature extremes into the total temperature change. Note 8: Slew rate is the slowest of the rising and falling slew rates. Note 9: Machine Model, 0Ω in series with 200pF. Note 10: Simulation results. Note 11: Short circuit test is a momentary test. Output short circuit duration is 1.5ms. Note 12: 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. Absolute maximum ratings indicate junction temperature limits beyond which the device may be permanently degraded, either mechanically or electrically. Ordering Information Package SOT23-5 Part Number Package Marking Transport Media NSC Drawing LMH6624MF A94A 1k Units Tape and Reel MF05A LMH6624MFX SOIC-8 LMH6624MA 3k Units Tape and Reel LMH6624MA 95 Units/Rail LMH6624MAX SOIC-8 LMH6626MA 2.5k Units Tape and Reel LMH6626MA 95 Units/Rail LMH6626MAX MSOP-8 LMH6626MM M08A M08A 2.5k Units Tape and Reel A98A 1k Units Tape and Reel LMH6626MMX MUA08A 3.5k Units Tape and Reel 5 www.national.com LMH6624/LMH6626 ± 6V Electrical Characteristics LMH6624/LMH6626 Typical Performance Characteristics Voltage Noise vs. Frequency Current Noise vs. Frequency 20058962 20058963 Inverting Frequency Response Inverting Frequency Response 20058989 20058988 Non-Inverting Frequency Response Non-Inverting Frequency Response 20058904 www.national.com 20058903 6 (Continued) Open Loop Frequency Response Over Temperature Open Loop Frequency Response Over Temperature 20058964 20058966 Frequency Response with Cap. Loading Frequency Response with Cap. Loading 20058984 20058986 Frequency Response with Cap. Loading Frequency Response with Cap. Loading 20058987 20058985 7 www.national.com LMH6624/LMH6626 Typical Performance Characteristics LMH6624/LMH6626 Typical Performance Characteristics (Continued) Non-Inverting Frequency Response Varying VIN Non-Inverting Frequency Response Varying VIN 20058906 20058905 Non-Inverting Frequency Response Varying VIN (LMH6626) Non-Inverting Frequency Response Varying VIN (LMH6624) 20058908 20058981 Non-Inverting Frequency Response Varying VIN (LMH6626) Non-Inverting Frequency Response Varying VIN (LMH6624) 20058907 www.national.com 20058980 8 (Continued) Sourcing Current vs. VOUT (LMH6624) Sourcing Current vs. VOUT (LMH6626) 20058957 20058972 Sourcing Current vs. VOUT (LMH6624) Sourcing Current vs. VOUT (LMH6626) 20058954 20058969 VOS vs. VSUPPLY (LMH6624) VOS vs. VSUPPLY (LMH6626) 20058967 20058968 9 www.national.com LMH6624/LMH6626 Typical Performance Characteristics LMH6624/LMH6626 Typical Performance Characteristics (Continued) Sinking Current vs. VOUT (LMH6624) Sinking Current vs. VOUT (LMH6626) 20058958 20058971 Sinking Current vs. VOUT (LMH6624) Sinking Current vs. VOUT (LMH6626) 20058956 20058970 IOS vs. VSUPPLY Crosstalk Rejection vs. Frequency (LMH6626) 20058979 20058953 www.national.com 10 LMH6624/LMH6626 Typical Performance Characteristics (Continued) Distortion vs. Frequency Distortion vs. Frequency 20058944 20058946 Distortion vs. Frequency Distortion vs. Gain 20058945 20058978 Distortion vs. VOUT Peak to Peak Distortion vs. VOUT Peak to Peak 20058943 20058977 11 www.national.com LMH6624/LMH6626 Typical Performance Characteristics (Continued) Non-Inverting Large Signal Pulse Response Non-Inverting Large Signal Pulse Response 20058973 20058974 Non-Inverting Small Signal Pulse Response Non-Inverting Small Signal Pulse Response 20058975 20058976 PSRR vs. Frequency PSRR vs. Frequency 20058948 www.national.com 20058949 12 (Continued) Input Referred CMRR vs. Frequency Input Referred CMRR vs. Frequency 20058901 20058902 Amplifier Peaking with Varying RF Amplifier Peaking with Varying RF 20058982 20058983 13 www.national.com LMH6624/LMH6626 Typical Performance Characteristics LMH6624/LMH6626 Application Section 20058919 20058918 FIGURE 2. Inverting Amplifier Configuration FIGURE 1. Non-Inverting Amplifier Configuration TOTAL INPUT NOISE vs. SOURCE RESISTANCE INTRODUCTION The LMH6624/LMH6626 are very wide gain bandwidth, ultra low noise voltage feedback operational amplifiers. Their excellent performances enable applications such as medical diagnostic ultrasound, magnetic tape & disk storage and fiber-optics to achieve maximum high frequency signal-tonoise ratios. The set of characteristic plots in the "Typical Performance" section illustrates many of the performance trade offs. The following discussion will enable the proper selection of external components to achieve optimum system performance. To determine maximum signal-to-noise ratios from the LMH6624/LMH6626, an understanding of the interaction between the amplifier’s intrinsic noise sources and the noise arising from its external resistors is necessary. Figure 3 describes the noise model for the non-inverting amplifier configuration showing all noise sources. In addition to the intrinsic input voltage noise (en) and current noise (in = in+ = in−) source, there is also thermal voltage noise (et = √(4KTR)) associated with each of the external resistors. Equation 1 provides the general form for total equivalent input voltage noise density (eni). Equation 2 is a simplification of Equation 1 that assumes BIAS CURRENT CANCELLATION To cancel the bias current errors of the non-inverting configuration, the parallel combination of the gain setting (Rg) and feedback (Rf) resistors should equal the equivalent source resistance (Rseq) as defined in Figure 1. Combining this constraint with the non-inverting gain equation also seen in Figure 1, allows both Rf and Rg to be determined explicitly from the following equations: Rf = AVRseq and Rg = Rf/(AV-1) When driven from a 0Ω source, such as the output of an op amp, the non-inverting input of the LMH6624/LMH6626 should be isolated with at least a 25Ω series resistor. As seen in Figure 2, bias current cancellation is accomplished for the inverting configuration by placing a resistor (Rb) on the non-inverting input equal in value to the resistance seen by the inverting input (Rf||(Rg+Rs)). Rb should to be no less than 25Ω for optimum LMH6624/LMH6626 performance. A shunt capacitor can minimize the additional noise of Rb. www.national.com 20058920 FIGURE 3. Non-Inverting Amplifier Noise Model 14 Rf||Rg should be as low as possible to minimize noise. Results similar to Equation 1 are obtained for the inverting configuration of Figure 2 if Rseq is replaced by Rb and Rg is replaced by Rg + Rs. With these substitutions, Equation 1 will yield an eni referred to the non-inverting input. Referring eni to the inverting input is easily accomplished by multiplying eni by the ratio of non-inverting to inverting gains. (Continued) (1) Rf||Rg = Rseq for bias current cancellation. Figure 4 illustrates the equivalent noise model using this assumption. Figure 5 is a plot of eni against equivalent source resistance (Rseq) with all of the contributing voltage noise source of Equation 2. This plot gives the expected eni for a given (Rseq) which assumes Rf||Rg = Rseq for bias current cancellation. The total equivalent output voltage noise (eno) is eni*AV. NOISE FIGURE Noise Figure (NF) is a measure of the noise degradation caused by an amplifier. (3) The Noise Figure formula is shown in Equation 3. The addition of a terminating resistor RT, reduces the external thermal noise but increases the resulting NF. The NF is increased because RT reduces the input signal amplitude thus reducing the input SNR. 20058921 FIGURE 4. Noise Model with Rf||Rg = Rseq (4) The noise figure is related to the equivalent source resistance (Rseq) and the parallel combination of Rf and Rg. To minimize noise figure. • Minimize Rf||Rg • Choose the Optimum RS (ROPT) ROPT is the point at which the NF curve reaches a minimum and is approximated by: ROPT ≈ en/in (2) As seen in Figure 5, eni is dominated by the intrinsic voltage noise (en) of the amplifier for equivalent source resistances below 33.5Ω. Between 33.5Ω and 6.43kΩ, eni is dominated by the thermal noise (et = √(4kT(2Rseq)) of the external resistor. Above 6.43kΩ, eni is dominated by the amplifier’s current noise (in = √(2) inRseq). When Rseq = 464Ω (ie., en/√(2) in) the contribution from voltage noise and current noise of LMH6624/LMH6626 is equal.. For example, configured with a gain of +20V/V giving a −3dB of 90MHz and driven from Rseq = 25Ω, the LMH6624 produces a total 1.57*90MHz) of equivalent input noise voltage (eni x 16.5µVrms. NON-INVERTING GAINS LESS THAN 10V/V Using the LMH6624/LMH6626 at lower non-inverting gains requires external compensation such as the shunt compensation as shown in Figure 6. The compensation capacitors are chosen to reduce frequency response peaking to less than 1dB. 20058924 FIGURE 6. External Shunt Compensation INVERTING GAINS LESS THAN 10V/V The lag compensation of Figure 7 will achieve stability for lower gains. It is best used for the inverting configuration because of its affect on the non-inverting input impedance. 20058922 FIGURE 5. Voltage Noise Density vs. Source Resistance If bias current cancellation is not a requirement, then Rf||Rg need not equal Rseq. In this case, according to Equation 1, 15 www.national.com LMH6624/LMH6626 Application Section LMH6624/LMH6626 Application Section (Continued) 20058927 20058925 FIGURE 9. Transimpedance Amplifier Configuration FIGURE 7. External Lag Compensation SINGLE SUPPLY OPERATION The LMH6624/LMH6626 can be operated with single power supply as shown in Figure 8. Both the input and output are capacitively coupled to set the DC operating point. 20058928 FIGURE 10. Current Noise Density vs. Feedback Resistance 20058926 FIGURE 8. Single Supply Operation LOW NOISE TRANSIMPEDANCE AMPLIFIER Figure 9 implements a low-noise transimpedance amplifier commonly used with photo-diodes. The transimpedance gain is set by Rf. Equation 4 provides the total input current noise density (ini) equation for the basic transimpedance configuration and is plotted against feedback resistance (Rf) showing all contributing noise sources in Figure 10. This plot indicates the expected total equivalent input current noise density (ini) for a given feedback resistance (Rf). The total equivalent output voltage noise density (eno) is ini*Rf. www.national.com (5) LOW NOISE INTEGRATOR The LMH6624/LMH6626 implement a deBoo integrator shown in Figure 11. Positive feedback maintains integration linearity. The LMH6624/LMH6626’s low input offset voltage and matched inputs allow bias current cancellation and provide for very precise integration. Keeping RG and RS low helps maintain dynamic stability. 16 LMH6624/LMH6626 Application Section (Continued) 20058931 FIGURE 13. Noise Magnetic Media Equalizer 20058929 FIGURE 11. Low Noise Integrator HIGH-GAIN SALLEN-KEY ACTIVE FILTERS The LMH6624/LMH6626 are well suited for high gain SallenKey type of active filters. Figure 12 shows the 2nd order Sallen-Key low pass filter topology. Using component predistortion methods discussed in OA-21 enables the proper selection of components for these high-frequency filters. 20058932 FIGURE 14. Equalizer Frequency Response LAYOUT CONSIDERATION National Semiconductor suggests the copper patterns on the evaluation boards listed below as a guide for high frequency layout. These boards are also useful as an aid in device testing and characterization. As is the case with all highspeed amplifiers, accepted-practice RF design technique on the PCB layout is mandatory. Generally, a good high frequency layout exhibits a separation of power supply and ground traces from the inverting input and output pins. Parasitic capacitances between these nodes and ground may cause frequency response peaking and possible circuit oscillations (see Application Note OA-15 for more information). Use high quality chip capacitors with values in the range of 1000pF to 0.1F for power supply bypassing. One terminal of each chip capacitor is connected to the ground plane and the other terminal is connected to a point that is as close as possible to each supply pin as allowed by the manufacturer’s design rules. In addition, connect a tantalum capacitor with a value between 4.7µF and 10µF in parallel with the chip capacitor. Signal lines connecting the feedback and gain resistors should be as short as possible to minimize inductance and microstrip line effect. Place input and output termination resistors as close as possible to the input/output pins. Traces greater than 1 inch in length should be impedance matched to the corresponding load termination. 20058930 FIGURE 12. Sallen-Key Active Filter Topology LOW NOISE MAGNETIC MEDIA EQUALIZER The LMH6624/LMH6626 implement a high-performance low noise equalizer for such application as magnetic tape channels as shown in Figure 13. The circuit combines an integrator with a bandpass filter to produce the low noise equalization. The circuit’s simulated frequency response is illustrated in Figure 14. 17 www.national.com LMH6624/LMH6626 Application Section by-product of the board layout and component placement. Moreover, a large resistor will also add more thermal noise to the signal path. Either way, keeping the resistor values low will diminish this interaction. On the other hand, choosing very low value resistors could load down nodes and will contribute to higher overall power dissipation and high distortion. (Continued) Symmetry between the positive and negative paths in the layout of differential circuitry should be maintained to minimize the imbalance of amplitude and phase of the differential signal. These free evaluation boards are shipped when a device sample request is placed with National Semiconductor. Component value selection is another important parameter in working with high speed/high performance amplifiers. Choosing external resistors that are large in value compared to the value of other critical components will affect the closed loop behavior of the stage because of the interaction of these resistors with parasitic capacitances. These parasitic capacitors could either be inherent to the device or be a www.national.com 18 Device Package Evaluation Board Part Number LMH6624MF SOT23–5 CLC730216 LMH6624MA SOIC-8 CLC730227 LMH6626MA SOIC-8 CLC730036 LMH6626MM MSOP-8 CLC730123 LMH6624/LMH6626 Physical Dimensions inches (millimeters) unless otherwise noted 5-Pin SOT23 NS Package Number MF05A 8-Pin SOIC NS Package Number M08A 19 www.national.com LMH6624/LMH6626 Single/Dual Ultra Low Noise Wideband Operational Amplifier Physical Dimensions inches (millimeters) unless otherwise noted (Continued) 8-Pin MSOP NS Package Number MUA08A 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. National Semiconductor Americas Customer Support Center Email: [email protected] Tel: 1-800-272-9959 www.national.com National Semiconductor Europe Customer Support Center Fax: +49 (0) 180-530 85 86 Email: [email protected] Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +44 (0) 870 24 0 2171 Français Tel: +33 (0) 1 41 91 8790 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 of the life support device or system, or to affect its safety or effectiveness. National Semiconductor Asia Pacific Customer Support Center Email: [email protected] National Semiconductor Japan Customer Support Center Fax: 81-3-5639-7507 Email: [email protected] 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.