LMH6682/6683 190MHz Single Supply, Dual and Triple Operational Amplifiers General Description The LMH6682 and LMH6683 are high speed operational amplifiers designed for use in modern video systems. These single supply monolithic amplifiers extend National’s featurerich, high value video portfolio to include a dual and a triple version. The important video specifications of differential gain ( ± 0.01% typ.) and differential phase ( ± 0.08 degrees) combined with an output drive current in each amplifier of 85mA make the LMH6682 and LMH6683 excellent choices for a full range of video applications. Voltage feedback topology in operational amplifiers assures maximum flexibility and ease of use in high speed amplifier designs. The LMH6682/83 is fabricated in National Semiconductor’s VIP10 process. This advanced process provides a superior ratio of speed to quiescient current consumption and assures the user of high-value amplifier designs. Advanced technology and circuit design enables in these amplifiers a −3db bandwidth of 190MHz, a slew rate of 940V/ µsec, and stability for gains of less than −1 and greater than +2. The input stage design of the LM6682/83 enables an input signal range that extends below the negative rail. The output stage voltage range reaches to within 0.8V of either rail when driving a 2kΩ load. Other attractive features include fast settling and low distortion. Other applications for these amplifiers include servo control designs. These applications are sensitive to amplifiers that exhibit phase reversal when the inputs exceed the rated voltage range. The LMH6682/83 amplifiers are designed to be immune to phase reversal when the specified input range is exceeded. See applications section. This feature makes for design simplicity and flexibility in many industrial applications. The LMH6682 dual operational amplifier is offered in miniature surface mount packages, SOIC-8, and MSOP-8. The LMH6683 triple amplifier is offered in SOIC-14 and TSSOP14. Features VS = ± 5V, TA = 25˚C, RL = 100Ω, A = +2 (Typical values unless specified) n DG error 0.01% n DP error 0.08˚ n −3dB BW (A = +2) 190MHz n Slew rate (VS = ± 5V) 940V/µs n Supply current 6.5mA/amp n Output current +80/−90mA n Input common mode voltage 0.5V beyond V−, 1.7V from V+ n Output voltage swing (RL = 2kΩ) 0.8V from rails n Input voltage noise (100KHz) 12nV/ Applications n n n n n CD/DVD ROM ADC buffer amp Portable video Current sense buffer Portable communications Connection Diagrams SOIC-8/MSOP-8 (LMH6682) SOIC-14/TSSOP-14 (LMH6683) 20059003 20059002 Top View © 2002 National Semiconductor Corporation DS200590 Top View www.national.com LMH6682/6683 190MHz Single Supply, Dual and Triple Operational Amplifiers November 2002 LMH6682/6683 Absolute Maximum Ratings Storage Temperature Range (Note 1) Junction Temperature (Note 7) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Supply Voltage (V+ – V−) 2KV(Note 2) Machine Model ± 2.5V Output Short Circuit Duration ± 10mA Supply Voltage (V+ - V−) Voltage at Input/Output pins 12.6V V+ +0.8V, V− −0.8V Soldering Information Infrared or Convection (20 sec.) 235˚C Wave Soldering (10 sec.) 260˚C −40˚C to +85˚C Package Thermal Resistance (Note 7) (Note 4), (Note 6) Input Current 3V to 12V Operating Temperature Range (Note 7) 200V (Note 3) VIN Differential +150˚C Operating Ratings (Note 1) ESD Tolerance Human Body Model −65˚C to +150˚C SOIC-8 190˚C/W MSOP-8 235˚C/W SOIC-14 145˚C/W TSSOP-14 155˚C/W 5V Electrical Characteristics Unless otherwise specified, all limits guaranteed for at TJ = 25˚C, V+ = 5V, V− = 0V, VO = VCM = V+/2, and RL = 100Ω to V+/2, RF = 510Ω. Boldface limits apply at the temperature extremes. Symbol SSBW Parameter −3dB BW Conditions A = +2, VOUT = 200mVPP Min (Note 9) 140 Typ (Note 8) 180 A = −1, VOUT = 200mVPP 180 Max (Note 9) Units MHz GFP Gain Flatness Peaking A = +2, VOUT = 200mVPP DC to 100MHz 2.1 dB GFR Gain Flatness Rolloff A = +2, VOUT = 200mVPP DC to 100MHz 0.1 dB LPD 1˚ 1˚ Linear Phase Deviation A = +2, VOUT = 200mVPP, ± 1˚ 40 MHz GF 0.1dB Gain Flatness A = +2, ± 0.1dB, VOUT = 200mVPP 25 MHz FPBW Full Power −1dB Bandwidth A = +2, VOUT = 2VPP 110 MHz DG Differential Gain NTSC 3.58MHz A = +2, RL = 150Ω to V+/2 Pos video only VCM = 2V 0.03 % DP Differential Phase NTSC 3.58MHz A = +2, RL = 150Ω to V+/2 Pos video only VCM = 2V 0.05 deg 20-80%, VO = 1VPP, AV = +2 2.1 20-80%, VO = 1VPP, AV = −1 2 Overshoot A = +2, VO = 100mVPP 22 % Ts Settling Time VO = 2VPP, ± 0.1%, AV = +2 49 ns SR Slew Rate (Note 11) A = +2, VOUT = 3VPP 520 A = −1, VOUT = 3VPP 500 f = 5MHz, VO = 2VPP, A = +2, RL = 2kΩ −60 f = 5MHz, VO = 2VPP, A = +2, RL = 100Ω −61 f = 5MHz, VO = 2VPP, A = +2, RL = 2kΩ −77 f = 5MHz, VO = 2VPP, A = +2, RL = 100Ω −54 0.1dB Time Domain Response Tr/Tf OS Rise and Fall Time ns V/µs Distortion and Noise Response HD2 HD3 2nd Harmonic Distortion 3rd Harmonic Distortion www.national.com 2 dBc dBc (Continued) Unless otherwise specified, all limits guaranteed for at TJ = 25˚C, V+ = 5V, V− = 0V, VO = VCM = V+/2, and RL = 100Ω to V+/2, RF = 510Ω. Boldface limits apply at the temperature extremes. Symbol Parameter Conditions Min (Note 9) Typ (Note 8) Max (Note 9) Units Distortion and Noise Response THD Total Harmonic Distortion f = 5MHz, VO = 2VPP, A = +2, RL = 2kΩ −60 f = 5MHz, VO = 2VPP, A = +2, RL = 100Ω −53 en Input Referred Voltage Noise f = 1kHz 17 f = 100kHz 12 in Input Referred Current Noise f = 1kHz 8 f = 100kHz 3 CT Cross-Talk Rejection (Amplifier) f = 5MHz, A = +2, SND: RL = 100Ω RCV: RF = RG = 510Ω dBc nV/ pA/ −77 dB Static, DC Performance AVOL CMVR Large Signal Voltage Gain Input Common-Mode Voltage Range VO = 1.25V to 3.75V, RL = 2kΩ to V+/2 85 95 VO = 1.5V to 3.5V, RL = 150Ω to V+/2 75 85 VO = 2V to 3V, RL = 50Ω to V+/2 70 80 −0.2 −0.1 −0.5 3.0 2.8 3.3 CMRR ≥ 50dB ± 1.1 VOS Input Offset Voltage TC VOS Input Offset Voltage Average Drift (Note 12) ±2 IB Input Bias Current (Note 10) −5 TC IB Input Bias Current Drift dB V ±5 ±7 mV µV/˚C −20 −30 0.01 µA nA/˚C IOS Input Offset Current CMRR Common Mode Rejection Ratio VCM Stepped from 0V to 3.0V 72 82 dB +PSRR Positive Power Supply Rejection Ratio V+ = 4.5V to 5.5V, VCM = 1V 70 76 dB IS Supply Current (per channel) No load 50 6.5 3 300 500 9 11 nA mA www.national.com LMH6682/6683 5V Electrical Characteristics LMH6682/6683 5V Electrical Characteristics (Continued) Unless otherwise specified, all limits guaranteed for at TJ = 25˚C, V+ = 5V, V− = 0V, VO = VCM = V+/2, and RL = 100Ω to V+/2, RF = 510Ω. Boldface limits apply at the temperature extremes. Symbol Parameter Conditions Min (Note 9) Typ (Note 8) RL = 2kΩ to V+/2 4.10 3.8 4.25 RL = 150Ω to V+/2 3.90 3.70 4.19 3.75 3.50 4.15 Max (Note 9) Units Miscellaneous Performance VO Output Swing High + RL = 75Ω to V /2 Output Swing Low RL = 2kΩ to V+/2 800 920 1100 RL = 150Ω to V+/2 870 970 1200 = 75Ω to V+/2 885 1100 1250 R IOUT ISC Output Current Output Short Circuit Current (Note 5), (Note 6), (Note 10) V L ± 40 +80/−75 Sourcing to V /2 −100 −80 −155 Sinking from V+/2 100 80 220 VO = 1V from either supply rail + RIN Common Mode Input Resistance 3 CIN Common Mode Input Capacitance 1.6 ROUT Output Resistance Closed Loop f = 1kHz, A = +2, RL = 50Ω 0.02 f = 1MHz, A = +2, RL = 50Ω 0.12 mV mA mA MΩ pF Ω ± 5V Electrical Characteristics Unless otherwise specified, all limits guaranteed for at TJ = 25˚C, V+ = 5V, V− = −5V, VO = VCM = 0V, and RL = 100Ω to 0V, RF = 510Ω. Boldface limits apply at the temperature extremes. Symbol SSBW Parameter −3dB BW Conditions A = +2, VOUT = 200mVPP Min (Note 9) 150 Typ (Note 8) 190 A = −1, VOUT = 200mVPP 190 Max (Note 9) Units MHz GFP Gain Flatness Peaking A = +2, VOUT = 200mVPP DC to 100MHz 1.7 dB GFR Gain Flatness Rolloff A = +2, VOUT = 200mVPP DC to 100MHz 0.1 dB LPD 1˚ 1˚ Linear Phase Deviation A = +2, VOUT = 200mVPP, ± 1˚ 40 MHz GF 0.1dB Gain Flatness A = +2, ± 0.1dB, VOUT = 200mVPP 25 MHz FPBW Full Power −1dB Bandwidth A = +2, VOUT = 2VPP 120 MHz DG Differential Gain NTSC 3.58MHz A = +2, RL = 150Ω to 0V 0.01 % DP Differential Phase NTSC 3.58MHz A = +2, RL = 150Ω to 0V 0.08 deg 20-80%, VO = 1VPP, A = +2 1.9 20-80%, VO = 1VPP, A = −1 2 0.1dB Time Domain Response Tr/Tf Rise and Fall Time ns OS Overshoot A = +2, VO = 100mVPP 19 % Ts Settling Time VO = 2VPP, ± 0.1%, A = +2 42 ns www.national.com 4 (Continued) Unless otherwise specified, all limits guaranteed for at TJ = 25˚C, V+ = 5V, V− = −5V, VO = VCM = 0V, and RL = 100Ω to 0V, RF = 510Ω. Boldface limits apply at the temperature extremes. Symbol Parameter Conditions Min (Note 9) Typ (Note 8) Max (Note 9) Units Time Domain Response SR Slew Rate (Note 11) A = +2, VOUT = 6VPP 940 A = −1, VOUT = 6VPP 900 f = 5MHz, VO = 2VPP, A = +2, RL = 2kΩ −63 f = 5MHz, VO = 2VPP, A = +2, RL = 100Ω −66 f = 5MHz, VO = 2VPP, A = +2, RL = 2kΩ −82 f = 5MHz, VO = 2VPP, A = +2, RL = 100Ω −54 f = 5MHz, VO = 2VPP, A = +2, RL = 2kΩ −63 f = 5MHz, VO = 2VPP, A = +2, RL = 100Ω −54 V/µs Distortion and Noise Response HD2 HD3 THD 2nd Harmonic Distortion 3rd Harmonic Distortion Total Harmonic Distortion en Input Referred Voltage Noise f = 1kHz 18 f = 100kHz 12 in Input Referred Current Noise f = 1kHz 6 f = 100kHz 3 CT Cross-Talk Rejection (Amplifier) dBc dBc dBc nV/ pA/ −78 f = 5MHz, A = +2, SND: RL = 100Ω RCV: RF = RG = 510Ω dB Static, DC Performance AVOL CMVR Large Signal Voltage Gain Input Common Mode Voltage Range VO = −3.75V to 3.75V, RL = 2kΩ to V+/2 87 100 VO = −3.5V to 3.5V, RL = 150Ω to V+/2 80 90 VO = −3V to 3V, RL = 50Ω to V+/2 75 85 −5.2 −5.1 −5.5 3.0 2.8 3.3 CMRR ≥ 50dB ±1 VOS Input Offset Voltage TC VOS Input Offset Voltage Average Drift (Note 12) ±2 IB Input Bias Current (Note 10) −5 TC IB Input Bias Current Drift dB V ±5 ±7 mV µV/˚C −20 −30 0.01 µA nA/˚C IOS Input Offset Current CMRR Common Mode Rejection Ratio VCM Stepped from −5V to 3.0V 75 84 dB +PSRR Positive Power Supply Rejection Ratio V+ = 8.5V to 9.5V, V− = −1V 75 82 dB −PSRR Negative Power Supply Rejection Ratio V− = −4.5V to −5.5V, V+ = 5V 78 85 dB 50 5 300 500 nA www.national.com LMH6682/6683 ± 5V Electrical Characteristics LMH6682/6683 ± 5V Electrical Characteristics (Continued) Unless otherwise specified, all limits guaranteed for at TJ = 25˚C, V+ = 5V, V− = −5V, VO = VCM = 0V, and RL = 100Ω to 0V, RF = 510Ω. Boldface limits apply at the temperature extremes. Symbol Parameter Conditions Min (Note 9) Typ (Note 8) Max (Note 9) 6.5 9.5 11 Units Static, DC Performance IS Supply Current (per channel) No load mA Miscellaneous Performance VO Output Swing High Output Swing Low RL = 2kΩ to 0V 4.10 3.80 4.25 RL = 150Ω to 0V 3.90 3.70 4.20 RL = 75Ω to 0V 3.75 3.50 4.18 V RL = 2kΩ to 0V −4.19 −4.07 −3.80 RL = 150Ω to 0V −4.05 −3.89 −3.65 R −4.00 −3.70 −3.50 L = 75Ω to 0V IOUT Output Current VO = 1V from either supply rail ± 45 +85/−80 ISC Output Short Circuit Current (Note 5) , (Note 6),(Note 10) Sourcing to 0V −120 −100 −180 Sinking from 0V 120 100 230 RIN Common Mode Input Resistance 4 CIN Common Mode Input Capacitance 1.6 ROUT Output Resistance Closed Loop f = 1kHz, A = +2, RL = 50Ω 0.02 f = 1MHz, A = +2, RL = 50Ω 0.12 mV mA mA MΩ pF Ω 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: Machine Model, 0Ω in series with 200pF. Note 4: 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 5: Short circuit test is a momentary test. See next note. Note 6: Output short circuit duration is infinite for VS < 6V at room temperature and below. For VS > 6V, allowable short circuit duration is 1.5ms. Note 7: 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 8: Typical values represent the most likely parametric norm. Note 9: All limits are guaranteed by testing or statistical analysis. Note 10: Positive current corresponds to current flowing into the device. Note 11: Slew rate is the average of the rising and falling slew rates Note 12: Offset Voltage average drift determined by dividing the change in VOS at temperature extremes into the total temperature change. www.national.com 6 LMH6682/6683 Typical Schematic 20059001 Ordering Information Package 8-Pin SOIC Part Number LMH6682MA LMH6682MAX 8-Pin MSOP LMH6682MM LMH6682MMX 14-Pin SOIC LMH6683MA LMH6683MAX 14-Pin TSSOP LMH6683MT LMH6683MTX Package Marking Transport Media 95 Units/Rail LMH6682MA 2.5k Units Tape and Reel 1k Units Tape and Reel A90A 2.5k Units Tape and Reel 55 Units/Rail LMH6683MA 2.5k Units Tape and Reel 94 Units/Rail LMH6683MT 2.5 Units Tape and Reel 7 NSC Drawing M08A MUA08A M14A MTC14 www.national.com LMH6682/6683 Typical Performance Characteristics At TA = 25˚C, V+ = +5V, V− = −5V, RF = 510Ω for A = +2; unless otherwise specified. Non-Inverting Frequency Response Inverting Frequency Response 20059004 20059006 Non-Inverting Frequency Response for Various Gain Inverting Frequency Response for Various Gain 20059005 20059007 Non-Inverting Phase vs. Frequency for Various Gain Inverting Phase vs. Frequency for Various Gain 20059024 www.national.com 20059025 8 (Continued) Open Loop Gain and Phase vs. Frequency Over Temperature Open Loop Gain & Phase vs. Frequency 20059008 20059057 Non-Inverting Frequency Response Over Temperature Inverting Frequency Response Over Temperature 20059038 20059037 Gain Flatness 0.1dB Differential Gain & Phase for A = +2 20059013 20059009 9 www.national.com LMH6682/6683 Typical Performance Characteristics LMH6682/6683 Typical Performance Characteristics (Continued) Transient Response Negative Transient Response Positive 20059012 20059010 Noise vs. Frequency Noise vs. Frequency 20059039 20059020 Harmonic Distortion vs. VOUT Harmonic Distortion vs. VOUT 20059044 20059045 www.national.com 10 LMH6682/6683 Typical Performance Characteristics (Continued) Harmonic Distortion vs. VOUT THD vs. for Various Frequencies 20059043 20059042 Harmonic Distortion vs. Frequency Crosstalk vs. Frequency 20059046 20059014 ROUT vs. Frequency IOS vs. VSUPPLY Over Temperature 20059021 20059023 11 www.national.com LMH6682/6683 Typical Performance Characteristics (Continued) VOS vs. VS @ −40˚C VOS vs. VS @ 25˚C 20059047 20059048 VOS vs. VS @ 85˚C VOS vs. VS @ 125˚C 20059049 20059050 VOS vs. VOUT VOS vs. VOUT 20059035 www.national.com 20059036 12 LMH6682/6683 Typical Performance Characteristics (Continued) ISUPPLY/Amp vs. VCM ISUPPLY/Amp vs. VSUPPLY 20059030 20059026 VOUT vs. ISOURCE VOUT vs. ISINK 20059031 20059033 VOUT vs. ISOURCE VOUT vs. ISINK 20059032 20059034 13 www.national.com LMH6682/6683 Typical Performance Characteristics (Continued) VOS vs. VCM |IB|vs. VS 20059064 20059028 Short Circuit ISOURCE vs. VS Short Circuit ISINK vs. VS 20059059 20059058 Linearity Input vs. Output Linearity Input vs. Output 20059041 www.national.com 20059040 14 LMH6682/6683 Typical Performance Characteristics (Continued) CMRR vs. Frequency PSRR vs. Frequency 20059011 20059022 Small Signal Pulse Response for A = +2 Small Signal Pulse Response A = −1 20059015 20059016 Large Signal Pulse Response Large Signal Pulse Response 20059017 20059018 15 www.national.com LMH6682/6683 Applications Section LARGE SIGNAL BEHAVIOR Amplifying high frequency signals with large amplitudes (as in video applications) has some special aspects to look after. The bandwidth of the Op Amp for large amplitudes is less than the small signal bandwidth because of slew rate limitations. While amplifying pulse shaped signals the slew rate properties of the OpAmp become more important at higher amplitude ranges. Due to the internal structure of an Op Amp the output can only change with a limited voltage difference per time unit (dV/dt). This can be explained as follows: To keep it simple, assume that an Op Amp consists of two parts; the input stage and the output stage. In order to stabilize the Op Amp, the output stage has a compensation capacitor in its feedback path. This Miller C integrates the current from the input stage and determines the pulse response of the Op Amp. The input stage must charge/discharge the feedback capacitor, as can be seen in Figure 1. 20059061 FIGURE 2. This property of the LMH6682/83 guaranties a higher slew rate at higher differential input voltages. ∆V/∆t = ∆V*Gm/C (5) In Figure 3 one can see that a higher transient voltage than will lead to a higher slew rate. 20059060 FIGURE 1. When a voltage transient is applied to the non inverting input of the Op Amp, the current from the input stage will charge the capacitor and the output voltage will slope up. The overall feedback will subtract the gradually increasing output voltage from the input voltage. The decreasing differential input voltage is converted into a current by the input stage (Gm). I*∆t = C *∆V (1) ∆V/∆t = I/C (2) I=∆V*Gm (3) where I = current t = time C = capacitance V = voltage Gm = transconductance Slew rate ∆V/∆t = volt/second In most amplifier designs the current I is limited for high differential voltages (Gm becomes zero). The slew rate will than be limited as well: ∆V/∆t = Imax/C (4) The LMH6682/83 has a different setup of the input stage. It has the property to deliver more current to the output stage when the input voltage is higher (class AB input). The current into the Miller capacitor exhibits an exponential character, while this current in other Op Amp designs reaches a saturation level at high input levels: (see Figure 2) www.national.com 20059062 FIGURE 3. HANDLING VIDEO SIGNALS When handling video signals, two aspects are very important especially when cascading amplifiers in a NTSC- or PAL video system. A composite video signal consists of both amplitude and phase information. The amplitude represents saturation while phase determines color (color burst is 3.59MHz for NTSC and 4.58MHz for PAL systems). In this case it is not only important to have an accurate amplification of the amplitude but also it is important not to add a varying phase shift to the video signals. It is a known phenomena that at different dc levels over a certain load the phase of the amplified signal will vary a little bit. In a video chain many amplifiers will be cascaded and all errors will be added together. For this reason, it is necessary to have strict requirements for the variation in gain and phase in conjunction to different dc levels. As can be seen in the tables the number for the differential gain for the LMH6682/83 is only 0.01% and for the differential phase it is only 0.08˚ at a supply voltage of ± 5V. Note that the phase is very depen16 interconnect them. The board becomes a real part itself, adding its own high frequency properties to the overall performance of the circuit. It’s good practice to have at least one ground plane on a PCB giving a low impedance path for all decouplings and other ground connections. Care should be taken especially that on board transmission lines have the same impedance as the cables they are connected to (i.e. 50Ω for most applications and 75Ω in case of video and cable TV applications). These transmission lines usually require much wider traces on a standard double sided PCB than needed for a ’normal’ connection. Another important issue is that inputs and outputs must not ’see’ each other or are routed together over the PCB at a small distance. Furthermore it is important that components are placed as flat as possible on the surface of the PCB. For higher frequencies a long lead can act as a coil, a capacitor or an antenna. A pair of leads can even form a transformer. Careful design of the PCB avoids oscillations or other unwanted behavior. When working with really high frequencies, the only components which can be used will be the surface mount ones (for more information see OA-15). As an example of how important the component values are for the behavior of your circuit, look at the following case: On a board with good high frequency layout, an amplifier is placed. For the two (equal) resistors in the feedback path, 5 different values are used to set the gain to +2. The resistors vary from 200Ω to 3kΩ. (Continued) dent of the load resistance, mainly because of the dc current delivered by the parts output stage into the load. For more information about differential gain and phase and how to measure it see National Semiconductors application note OA-24 which can be found on via Nationals home page http://www.national.com OUTPUT PHASE REVERSAL This is a problem with some operational amplifiers. This effect is caused by phase reversal in the input stage due to saturation of one or more of the transistors when the inputs exceed the normal expected range of voltages. Some applications, such as servo control loops among others, are sensitive to this kind of behavior and would need special safeguards to ensure proper functioning. The LMH6682/ 6683 is immune to output phase reversal with input overload. With inputs exceeded, the LMH6682/6683 output will stay at the clamped voltage from the supply rail. Exceeding the input supply voltages beyond the Absolute Maximum Ratings of the device could however damage or otherwise adversely effect the reliability or life of the device. DRIVING CAPACITIVE LOADS The LMH6682/6683 can drive moderate values of capacitance by utilizing a series isolation resistor between the output and the capacitive load. Capacitive load tolerance will improve with higher closed loop gain values. Applications such as ADC buffers, among others, present complex and varying capacitive loads to the Op Amp; best value for this isolation resistance is often found by experimentation and actual trial and error for each application. DISTORTION Applications with demanding distortion performance requirements are best served with the device operating in the inverting mode. The reason for this is that in the inverting configuration, the input common mode voltage does not vary with the signal and there is no subsequent ill effects due to this shift in operating point and the possibility of additional non-linearity. Moreover, under low closed loop gain settings (most suited to low distortion), the non-inverting configuration is at a further disadvantage of having to contend with the input common voltage range. There is also a strong relationship between output loading and distortion performance (i.e. 2kΩ vs. 100Ω distortion improves by about 15dB @1MHz) especially at the lower frequency end where the distortion tends to be lower. At higher frequency, this dependence diminishes greatly such that this difference is only about 5dB at 10MHz. But, in general, lighter output load leads to reduced HD3 term and thus improves THD. (see the curve THD vs. VOUT over various frequencies). 20059063 FIGURE 4. In Figure 4 can be seen that there’s more peaking with higher resistor values, which can lead to oscillations and bad pulse responses. On the other hand the low resistor values will contribute to higher overall power consumption. NSC suggests the following evaluation boards as a guide for high frequency layout and as an aid in device testing and characterization. PRINTED CIRCUIT BOARD LAYOUT AND COMPONENT VALUES SELECTION Generally it is a good idea to keep in mind that for a good high frequency design both the active parts and the passive ones are suitable for the purpose you are using them for. Amplifying frequencies of several hundreds of MHz is possible while using standard resistors but it makes life much easier when using surface mount ones. These resistors (and capacitors) are smaller and therefore parasitics have lower values and will have less influence on the properties of the amplifier. Another important issue is the PCB, which is no longer a simple carrier for all the parts and a medium to Device Package Evaluation Board PN LMH6682MA 8-Pin SOIC CLC730036 LMH6682MM 8-Pin MSOP CLC730123 LMH6683MA 14-Pin SOIC CLC730031 LMH6683MT 14-Pin TSSOP CLC730131 These free evaluation boards are shipped when a device sample request is placed with National Semiconductor. 17 www.national.com LMH6682/6683 Applications Section LMH6682/6683 Physical Dimensions inches (millimeters) unless otherwise noted 8-Pin SOIC NS Package Number M08A 8-Pin MSOP NS Package Number MUA08A www.national.com 18 LMH6682/6683 Physical Dimensions inches (millimeters) unless otherwise noted (Continued) 14-Pin SOIC NS Package Number M14A 14-Pin TSSOP NS Package Number MTC14 19 www.national.com LMH6682/6683 190MHz Single Supply, Dual and Triple Operational Amplifiers Notes 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 Corporation Americas Email: [email protected] www.national.com National Semiconductor Europe 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 Response Group Tel: 65-2544466 Fax: 65-2504466 Email: [email protected] National Semiconductor Japan Ltd. Tel: 81-3-5639-7560 Fax: 81-3-5639-7507 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.