LMH6642/6643/6644 3V, Low Power, 130MHz, 75mA Rail-to-Rail Output Amplifiers General Description The LMH664X family true single supply voltage feedback amplifiers offer high speed (130MHz), low distortion (−62dBc), and exceptionally high output current (approximately 75mA) at low cost and with reduced power consumption when compared against existing devices with similar performance. Input common mode voltage range extends to 0.5V below V− and 1V from V+. Output voltage range extends to within 40mV of either supply rail, allowing wide dynamic range especially desirable in low voltage applications. The output stage is capable of approximately 75mA in order to drive heavy loads. Fast output Slew Rate (130V/µs) ensures large peak-to-peak output swings can be maintained even at higher speeds, resulting in exceptional full power bandwidth of 40MHz with a 3V supply. These characteristics, along with low cost, are ideal features for a multitude of industrial and commercial applications. Careful attention has been paid to ensure device stability under all operating voltages and modes. The result is a very well behaved frequency response characteristic (0.1dB gain flatness up the 12MHz under 150Ω load and AV = +2) with minimal peaking (typically 2dB maximum) for any gain setting and under both heavy and light loads. This along with fast settling time (68ns) and low distortion allows the device to operate well in ADC buffer, and high frequency filter applications as well as other applications. This device family offers professional quality video performance with low DG (0.01%) and DP (0.01˚) characteristics. Differential Gain and Differential Phase characteristics are also well maintained under heavy loads (150Ω) and throughout the output voltage range. The LMH664X family is offered Closed Loop Gain vs. Frequency for Various Gain 20018535 © 2002 National Semiconductor Corporation DS200185 in single (LMH6642), dual (LMH6643), and quad (LMH6644) options. See ordering information for packages offered. Features (VS = ± 5V, TA = 25˚C, RL = 2kΩ, AV = +1. Typical values unless specified). n −3dB BW (AV = +1) 130MHz n Supply voltage range 3V to 12.8V n Slew rate (Note 8), (AV = −1) 130V/µs n Supply current (no load) 2.7mA/amp n Output short circuit current +115mA/−145mA ± 75mA n Linear output current n Input common mode volt. 0.5V beyond V−, 1V from V+ n Output voltage swing 40mV from rails n Input voltage noise (100kHz) 17nV/ n Input current noise (100kHz) 0.9pA/ n THD (5MHz, RL = 2kΩ, VO = 2VPP, AV = +2) −62dBc n Settling time 68ns n Fully characterized for 3V, 5V, and ± 5V n Overdrive recovery 100ns n Output short circuit protected (Note 11) n No output phase reversal with CMVR exceeded Applications n n n n n Active filters CD/DVD ROM ADC buffer amp Portable video Current sense buffer Large Signal Frequency Response 20018547 www.national.com LMH6642/6643/6644 3V, Low Power, 130MHz, 75mA Rail-to-Rail Output Amplifiers January 2002 LMH6642/6643/6644 Absolute Maximum Ratings (Note 1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. ESD Tolerance Supply Voltage (V - V ) Voltage at Input/Output pins 13.5V V+ +0.8V, V− −0.8V ± 10mA Input Current Storage Temperature Range −65˚C to +150˚C Junction Temperature (Note 4) 3V to 12.8V −40˚C to +85˚C Package Thermal Resistance (Note 4) (θJA) (Note 3), (Note 11) − 260˚C Junction Temperature Range (Note 4) ± 2.5V + Wave Soldering Lead Temp.(10 sec) Supply Voltage (V+ – V−) 200V (Note 9) Output Short Circuit Duration 235˚C Operating Ratings (Note 1) 2KV (Note 2) VIN Differential Infrared or Convection Reflow(20 sec) +150˚C SOT23-5 265˚C/W SOIC-8 190˚C/W MSOP-8 235˚C/W SOIC-14 145˚C/W TSSOP-14 155˚C/W Soldering Information 3V Electrical Characteristics Unless otherwise specified, all limits guaranteed for at TJ = 25˚C, V+ = 3V, V− = 0V, VCM = VO = V+/2, and RL = 2kΩ to V+/2. Boldface limits apply at the temperature extremes. Symbol BW Parameter −3dB BW Conditions AV = +1, VOUT = 200mVPP Min (Note 6) Typ (Note 5) 80 115 AV = +2, −1, VOUT = 200mVPP 46 Max (Note 6) Units MHz BW0.1dB 0.1dB Gain Flatness AV = +2, RL = 150Ω to V+/2, RL = 402Ω, VOUT = 200mVPP 19 MHz PBW Full Power Bandwidth AV = +1, −1dB, VOUT = 1VPP 40 MHz en Input-Referred Voltage Noise in Input-Referred Current Noise f = 100kHz 17 f = 1kHz 48 f = 100kHz 0.90 f = 1kHz 3.3 THD Total Harmonic Distortion f = 5MHz, VO = 2VPP, AV = −1, RL = 100Ω to V+/2 −48 DG Differential Gain VCM = 1V, NTSC, AV = +2 RL =150Ω to V+/2 0.17 Differential Phase pA/ dBc % RL =1kΩ to V+/2 DP nV/ 0.03 VCM = 1V, NTSC, AV = +2 RL =150Ω to V+/2 0.05 deg RL =1kΩ to V+/2 0.03 CT Rej. Cross-Talk Rejection f = 5MHz, Receiver: Rf = Rg = 510Ω, AV = +2 47 dB TS Settling Time VO = 2VPP, ± 0.1%, 8pF Load, VS = 5V 68 ns SR Slew Rate (Note 8) AV = −1, VI = 2VPP VOS Input Offset Voltage TC VOS Input Offset Average Drift (Note 12) ±5 IB Input Bias Current (Note 7) −1.50 −2.60 −3.25 µA IOS Input Offset Current 20 800 1000 nA RIN Common Mode Input Resistance 3 MΩ CIN Common Mode Input Capacitance 2 pF www.national.com 90 120 ±1 2 V/µs ±5 ±7 mV µV/˚C (Continued) Unless otherwise specified, all limits guaranteed for at TJ = 25˚C, V+ = 3V, V− = 0V, VCM = VO = V+/2, and RL = 2kΩ to V+/2. Boldface limits apply at the temperature extremes. Symbol CMVR Parameter Input Common-Mode Voltage Range Conditions Min (Note 6) CMRR ≥ 50dB Typ (Note 5) Max (Note 6) −0.5 −0.2 −0.1 1.8 1.6 2.0 CMRR Common Mode Rejection Ratio VCM Stepped from 0V to 1.5V 72 95 AVOL Large Signal Voltage Gain VO = 0.5V to 2.5V RL = 2kΩ to V+/2 80 75 96 VO = 0.5V to 2.5V RL = 150Ω to V+/2 74 70 82 VO ISC dB RL = 2kΩ to V+/2, VID = 200mV 2.90 2.98 RL = 150Ω to V+/2, VID = 200mV 2.80 2.93 Output Swing Low RL = 2kΩ to V+/2, VID = −200mV 25 75 + 75 150 Output Short Circuit Current Sourcing to V+/2 VID = 200mV (Note 10) 50 35 95 Sinking to V+/2 VID = −200mV (Note 10) 55 40 110 IOUT Output Current VOUT = 0.5V from either supply +PSRR Positive Power Supply Rejection Ratio V+ = 3.0V to 3.5V, VCM = 1.5V IS Supply Current (per channel) No Load 75 V dB Output Swing High RL = 150Ω to V /2, VID = −200mV Units V mV mA ± 65 mA 85 dB 2.70 4.00 4.50 mA 5V Electrical Characteristics Unless otherwise specified, all limits guaranteed for at TJ = 25˚C, V+ = 5V, V− = 0V, VCM = VO = V+/2, and RL = 2kΩ to V+/2. Boldface limits apply at the temperature extremes. Symbol Parameter BW −3dB BW BW0.1dB 0.1dB Gain Flatness Conditions AV = +1, VOUT = 200mVPP Min (Note 6) Typ (Note 5) 90 120 AV = +2, RL = 150Ω to V+/2, Rf = 402Ω, VOUT = 200mVPP 15 MHz MHz Full Power Bandwidth AV = +1, −1dB, VOUT = 2VPP 22 Input-Referred Voltage Noise f = 100kHz 17 f = 1kHz 48 f = 100kHz 0.90 f = 1kHz 3.3 THD Total Harmonic Distortion f = 5MHz, VO = 2VPP, AV = +2 −60 DG Differential Gain NTSC, AV = +2 RL =150Ω to V+/2 0.16 RL =1kΩ to V+/2 0.05 NTSC, AV = +2 RL =150Ω to V+/2 0.05 RL =1kΩ to V+/2 0.01 DP Differential Phase MHz 46 en Input-Referred Current Noise Units AV = +2, −1, VOUT = 200mVPP PBW in Max (Note 6) nV/ pA/ dBc % deg CT Rej. Cross-Talk Rejection f = 5MHz, Receiver: Rf = Rg = 510Ω, AV = +2 47 dB TS Settling Time VO = 2VPP, ± 0.1%, 8pF Load 68 ns 3 www.national.com LMH6642/6643/6644 3V Electrical Characteristics LMH6642/6643/6644 5V Electrical Characteristics (Continued) Unless otherwise specified, all limits guaranteed for at TJ = 25˚C, V+ = 5V, V− = 0V, VCM = VO = V+/2, and RL = 2kΩ to V+/2. Boldface limits apply at the temperature extremes. Symbol Parameter Conditions SR Slew Rate (Note 8) AV = −1, VI = 2VPP VOS Input Offset Voltage Min (Note 6) Typ (Note 5) 95 125 ±1 Input Offset Average Drift (Note 12) Input Bias Current (Note 7) IOS Input Offset Current RIN Common Mode Input Resistance 3 CIN Common Mode Input Capacitance 2 CMVR Input Common-Mode Voltage Range CMRR ≥ 50dB µV/˚C µA 20 800 1000 nA 3.8 3.6 4.0 72 95 Common Mode Rejection Ratio VCM Stepped from 0V to 3.5V AVOL Large Signal Voltage Gain VO = 0.5V to 4.50V RL = 2kΩ to V+/2 86 82 98 VO = 0.5V to 4.25V RL = 150Ω to V+/2 76 72 82 MΩ pF −0.2 −0.1 dB RL = 2kΩ to V+/2, VID = 200mV 4.90 4.98 RL = 150Ω to V+/2, VID = 200mV 4.65 4.90 Output Swing Low RL = 2kΩ to V+/2, VID = −200mV 25 100 + 100 150 Output Short Circuit Current Sourcing to V+/2 VID = 200mV (Note 10) 55 40 115 Sinking to V+/2 VID = −200mV (Note 10) 70 55 140 Output Current VO = 0.5V from either supply +PSRR Positive Power Supply Rejection Ratio V+ = 4.0V to 6V IS Supply Current (per channel) No Load V mV mA ± 70 79 V dB Output Swing High IOUT mV −1.70 CMRR ISC ±5 ±7 −2.60 −3.25 −0.5 RL = 150Ω to V /2, VID = −200mV Units V/µs ±5 TC VOS IB VO Max (Note 6) mA dB 90 2.70 4.25 5.00 mA ± 5V Electrical Characteristics Unless otherwise specified, all limits guaranteed for at TJ = 25˚C, V+ = 5V, V− = −5V, VCM = VO = 0V and RL = 2kΩ to ground. Boldface limits apply at the temperature extremes. Symbol Parameter BW −3dB BW BW0.1dB 0.1dB Gain Flatness Conditions AV = +1, VOUT = 200mVPP Min (Note 6) Typ (Note 5) 95 130 Units MHz AV = +2, −1, VOUT = 200mVPP 46 AV = +2, RL = 150Ω to V+/2, Rf = 806Ω, VOUT = 200mVPP 12 MHz MHz PBW Full Power Bandwidth AV = +1, −1dB, VOUT = 2VPP 24 en Input-Referred Voltage Noise f = 100kHz 17 f = 1kHz 48 www.national.com Max (Note 6) 4 nV/ (Continued) Unless otherwise specified, all limits guaranteed for at TJ = 25˚C, V+ = 5V, V− = −5V, VCM = VO = 0V and RL = 2kΩ to ground. Boldface limits apply at the temperature extremes. Symbol Parameter Conditions Min (Note 6) Typ (Note 5) in Input-Referred Current Noise f = 100kHz 0.90 f = 1kHz 3.3 THD Total Harmonic Distortion f = 5MHz, VO = 2VPP, AV = +2 −62 DG Differential Gain NTSC, AV = +2 RL =150Ω to V+/2 0.15 + DP Differential Phase RL =1kΩ to V /2 0.01 NTSC, AV = +2 RL =150Ω to V+/2 0.04 RL =1kΩ to V+/2 0.01 CT Rej. Cross-Talk Rejection f = 5MHz, Receiver: Rf = Rg = 510Ω, AV = +2 47 TS Settling Time VO = 2VPP, ± 0.1%, 8pF Load, VS = 5V 68 SR Slew Rate (Note 8) AV = −1, VI = 2VPP VOS Input Offset Voltage 100 ±1 Input Offset Average Drift (Note 12) Input Bias Current (Note 7) IOS Input Offset Current RIN Common Mode Input Resistance 3 CIN Common Mode Input Capacitance 2 CMVR Input Common-Mode Voltage Range deg dB ns V/µs ±5 ±7 CMRR ≥ 50dB µV/˚C µA 20 800 1000 nA −5.5 3.8 3.6 4.0 74 95 VCM Stepped from −5V to 3.5V AVOL Large Signal Voltage Gain VO = −4.5V to 4.5V, RL = 2kΩ 88 84 96 VO = −4.0V to 4.0V, RL = 150Ω 78 74 82 MΩ pF −5.2 −5.1 dB RL = 2kΩ, VID = 200mV 4.90 4.96 RL = 150Ω, VID = 200mV 4.65 4.80 Output Swing Low RL = 2kΩ, VID = −200mV −4.96 −4.90 RL = 150Ω, VID = −200mV −4.80 −4.65 Output Short Circuit Current Sourcing to Ground VID = 200mV (Note 10) 60 35 115 Sinking to Ground VID = −200mV (Note 10) 85 65 145 VO = 0.5V from either supply + V Power Supply Rejection Ratio (V , V ) = (4.5V, −4.5V) to (5.5V, −5.5V) ± 75 IS Supply Current (per channel) No Load 78 mA dB 90 2.70 5 V mA − PSRR V dB Output Swing High Output Current mV −1.60 Common Mode Rejection Ratio IOUT % −2.60 −3.25 CMRR ISC dBc ±5 TC VOS Units pA/ 135 IB VO Max (Note 6) 4.50 5.50 mA www.national.com LMH6642/6643/6644 ± 5V Electrical Characteristics LMH6642/6643/6644 ± 5V Electrical Characteristics (Continued) 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: Positive current corresponds to current flowing into the device. Note 8: Slew rate is the average of the rising and falling slew rates. Note 9: Machine Model, 0Ω in series with 200pF. Note 10: Short circuit test is a momentary test. See Note 11. Note 11: 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 12: Offset voltage average drift determined by dividing the change in VOS at temperature extremes by the total temperature change. Connection Diagrams SOT23-5 (LMH6642) SOIC-8 and MSOP-8 (LMH6643) SOIC-8 (LMH6642) 20018561 Top View 20018562 Top View 20018563 Top View SOIC-14 and TSSOP-14 (LMH6644) 20018568 Top View www.national.com 6 At TJ = 25˚C, V+ = +5, V− = −5V, RF = RL = 2kΩ. Unless otherwise specified. Closed Loop Frequency Response for Various Supplies Closed Loop Gain vs. Frequency for Various Gain 20018557 20018551 Closed Loop Frequency Response for Various Temperature Closed Loop Gain vs. Frequency for Various Gain 20018550 20018535 Closed Loop Frequency Response for Various Temperature Closed Loop Gain vs. Frequency for Various Supplies 20018548 20018534 7 www.national.com LMH6642/6643/6644 Typical Performance Characteristics LMH6642/6643/6644 Typical Performance Characteristics At TJ = 25˚C, V+ = +5, V− = −5V, RF = RL = 2kΩ. Unless otherwise specified. (Continued) Closed Loop Small Signal Frequency Response for Various Supplies Large Signal Frequency Response 20018546 20018547 ± 0.1dB Gain Flatness for Various Supplies Closed Loop Frequency Response for Various Supplies 20018544 20018545 VOUT (VPP) for THD < 0.5% VOUT (VPP) for THD < 0.5% 20018509 www.national.com 20018508 8 At TJ = 25˚C, V+ = +5, V− = −5V, RF = RL = 2kΩ. Unless otherwise specified. (Continued) VOUT (VPP) for THD < 0.5% Open Loop Gain/Phase for Various Temperature 20018532 20018510 Open Loop Gain/Phase for Various Temperature HD2 (dBc) vs. Output Swing 20018533 20018514 HD3 (dBc) vs. Output Swing HD2 vs. Output Swing 20018504 20018515 9 www.national.com LMH6642/6643/6644 Typical Performance Characteristics LMH6642/6643/6644 Typical Performance Characteristics At TJ = 25˚C, V+ = +5, V− = −5V, RF = RL = 2kΩ. Unless otherwise specified. (Continued) HD3 vs. Output Swing THD (dBc) vs. Output Swing 20018505 20018506 Settling Time vs. Input Step Amplitude (Output Slew and Settle Time) Input Noise vs. Frequency 20018512 20018513 + − VOUT from V vs. ISOURCE VOUT from V vs. ISINK 20018518 www.national.com 20018519 10 At TJ = 25˚C, V+ = +5, V− = −5V, RF = RL = 2kΩ. Unless otherwise specified. (Continued) VOUT from V+ vs. ISOURCE VOUT from V− vs. ISINK 20018516 20018517 Swing vs. VS Short Circuit Current (to VS/2) vs. VS 20018529 20018531 Output Sinking Saturation Voltage vs. IOUT Output Sourcing Saturation Voltage vs. IOUT 20018520 20018501 11 www.national.com LMH6642/6643/6644 Typical Performance Characteristics LMH6642/6643/6644 Typical Performance Characteristics At TJ = 25˚C, V+ = +5, V− = −5V, RF = RL = 2kΩ. Unless otherwise specified. (Continued) Closed Loop Output Impedance vs. Frequency AV = +1 PSRR vs. Frequency 20018502 20018503 Crosstalk Rejection vs. Frequency (Output to Output) CMRR vs. Frequency 20018507 20018511 VOS vs. VOUT (Typical Unit) VOS vs. VCM (Typical Unit) 20018527 20018530 www.national.com 12 At TJ = 25˚C, V+ = +5, V− = −5V, RF = RL = 2kΩ. Unless otherwise specified. (Continued) VOS vs. VS (for 3 Representative Units) VOS vs. VS (for 3 Representative Units) 20018522 20018523 VOS vs. VS (for 3 Representative Units) IB vs. VS 20018525 20018524 IOS vs. VS IS vs. VCM 20018528 20018526 13 www.national.com LMH6642/6643/6644 Typical Performance Characteristics LMH6642/6643/6644 Typical Performance Characteristics At TJ = 25˚C, V+ = +5, V− = −5V, RF = RL = 2kΩ. Unless otherwise specified. (Continued) IS vs. VS Small Signal Step Response 20018553 20018521 Large Signal Step Response Large Signal Step Response 20018541 20018539 Small Signal Step Response Small Signal Step Response 20018556 www.national.com 20018536 14 At TJ = 25˚C, V+ = +5, V− = −5V, RF = RL = 2kΩ. Unless otherwise specified. (Continued) Small Signal Step Response Small Signal Step Response 20018552 20018538 Large Signal Step Response Large Signal Step Response 20018537 20018554 Large Signal Step Response 20018560 15 www.national.com LMH6642/6643/6644 Typical Performance Characteristics LMH6642/6643/6644 Application Notes Circuit Description: This device family was designed to avoid output phase reversal. With input overdrive, the output is kept near supply rail (or as closed to it as mandated by the closed loop gain setting and the input voltage). See Figure 1: The LMH664X family is based on National Semiconductor’s proprietary VIP10 dielectrically isolated bipolar process. This device family architecture features the following: • Complimentary bipolar devices with exceptionally high ft (∼8GHz) even under low supply voltage (2.7V) and low bias current. • A class A-B “turn-around” stage with improved noise, offset, and reduced power dissipation compared to similar speed devices (patent pending). • Common Emitter push-push output stage capable of 75mA output current (at 0.5V from the supply rails) while consuming only 2.7mA of total supply current per channel. This architecture allows output to reach within milli-volts of either supply rail. • Consistent performance from any supply voltage (3V-10V) with little variation with supply voltage for the most important specifications (e.g. BW, SR, IOUT, etc.) • Significant power saving (∼40%) compared to competitive devices on the market with similar performance. Application Hints: This Op Amp family is a drop-in replacement for the AD805X family of high speed Op Amps in most applications. In addition, the LMH664X will typically save about 40% on power dissipation, due to lower supply current, when compared to competition. All AD805X family’s guaranteed parameters are included in the list of LMH664X guaranteed specifications in order to ensure equal or better level of performance. However, as in most high performance parts, due to subtleties of applications, it is strongly recommended that the performance of the part to be evaluated is tested under actual operating conditions to ensure full compliance to all specifications. With 3V supplies and a common mode input voltage range that extends 0.5V below V−, the LMH664X find applications in low voltage/low power applications. Even with 3V supplies, the −3dB BW (@ AV = +1) is typically 115MHz with a tested limit of 80MHz. Production testing guarantees that process variations with not compromise speed. High frequency response is exceptionally stable confining the typical -3dB BW over the industrial temperature range to ± 2.5%. As can be seen from the typical performance plots, the LMH664X output current capability (∼75mA) is enhanced compared to AD805X. This enhancement, increases the output load range, adding to the LMH664X’s versatility. Because of the LMH664X’s high output current capability attention should be given to device junction temperature in order not to exceed the Absolute Maximum Rating. www.national.com 20018542 FIGURE 1. Input and Output Shown with CMVR Exceeded However, if the input voltage range of −0.5V to 1V from V+ is exceeded by more than a diode drop, the internal ESD protection diodes will start to conduct.The current in the diodes should be kept at or below 10mA. Output overdrive recovery time is less than 100ns as can be seen from Figure 2 plot: 20018543 FIGURE 2. Overload Recovery Waveform 16 Amp input capacitance and Q1 equivalent collector capacitance together (CIN) will cause additional phase shift to the signal fed back to the inverting node. Cf will function as a zero in the feedback path counter-acting the effect of the CIN and acting to stabilized the circuit. By proper selection of Cf such that the Op Amp open loop gain is equal to the inverse of the feedback factor at that frequency, the response is optimized with a theoretical 45˚ phase margin. (Continued) Single Supply, Low Power Photodiode Amplifier: The circuit shown in Figure 3 is used to amplify the current from a photo-diode into a voltage output. In this circuit, the emphasis is on achieving high bandwidth and the transimpedance gain setting is kept relatively low. Because of its high slew rate limit and high speed, the LMH664X family lends itself well to such an application. This circuit achieves approximately 1V/mA of transimpedance gain and capable of handling up to 1mApp from the photodiode. Q1, in a common base configuration, isolates the high capacitance of the photodiode (Cd) from the Op Amp input in order to maximize speed. Input is AC coupled through C1 to ease biasing and allow single supply operation. With 5V single supply, the device input/output is shifted to near half supply using a voltage divider from VCC. Note that Q1 collector does not have any voltage swing and the Miller effect is minimized. D1, tied to Q1 base, is for temperature compensation of Q1’s bias point. Q1 collector current was set to be large enough to handle the peak-to-peak photodiode excitation and not too large to shift the U1 output too far from mid-supply. No matter how low an Rf is selected, there is a need for Cf in order to stabilize the circuit. The reason for this is that the Op (1) where GBWP is the Gain Bandwidth Product of the Op Amp Optimized as such, the I-V converter will have a theoretical pole, fp, at: (2) With Op Amp input capacitance of 3pF and an estimate for Q1 output capacitance of about 3pF as well, CIN = 6pF. From the typical performance plots, LMH6642/6643 family GBWP is approximately 57MHz. Therefore, with Rf = 1k, from Equation 1 and 2 above. Cf = ∼4.1pF, and fp = 39MHz 20018564 FIGURE 3. Single Supply Photodiode I-V Converter 17 www.national.com LMH6642/6643/6644 Application Notes LMH6642/6643/6644 Application Notes Printed Circuit Board Layout and Component Values Sections: (Continued) For this example, optimum Cf was empirically determined to be around 5pF. This time domain response is shown in Figure 4 below showing about 9ns rise/fall times, corresponding to about 39MHz for fp. The overall supply current from the +5V supply is around 5mA with no load. Generally, a good high frequency layout will keep power supply and ground traces away from the inverting input and output pins. Parasitic capacitances on these nodes to ground will cause frequency response peaking and possible circuit oscillations (see Application Note OA-15 for more information). National Semiconductor suggests the following evaluation boards as a guide for high frequency layout and as an aid in device testing and characterization: Device Package Evaluation Board PN LMH6642MF SOT23-5 CLC730068 LMH6642MA 8-Pin SOIC CLC730027 LMH6643MA 8-Pin SOIC CLC730036 LMH6643MM 8-Pin MSOP CLC730123 LMH6644MA 14-Pin SOIC CLC730031 These free evaluation boards are shipped when a device sample request is placed with National Semiconductor. Another important parameter in working with high speed/high performance amplifiers, is the component values selection. Choosing external resistors that are large in value will effect the closed loop behavior of the stage because of the interaction of these resistors with parasitic capacitances. These capacitors could be inherent to the device or a by-product of the board layout and component placement. Either way, keeping the resistor values lower, will diminish this interaction to a large extent. On the other hand, choosing very low value resistors could load down nodes and will contribute to higher overall power dissipation. 20018565 FIGURE 4. Converter Step Response (1VPP, 20 ns/DIV) Ordering Information Package Part Number Package Marking Transport Media NSC Drawing 5-Pin SOT-23 LMH6642MF A64A 1k Units Tape and Reel MF05A LMH6642MFX SOIC-8 LMH6642MA 3k Units Tape and Reel LMH6642MA LMH6642MAX LMH6643MA LMH6643MA LMH6643MAX MSOP-8 LMH6643MM LMH6644MA LMH6644MT 1k Units Tape and Reel LMH6644MA MUA08A Rails M14A 2.5k Units Tape and Reel LMH6644MT LMH6644MTX www.national.com Rails 3.5k Units Tape and Reel LNH6644MAX TSSOP-14 M08A 2.5k Units Tape and Reel A65A LMH6643MMX SOIC-14 Rails 2.5k Units Tape and Reel Rails 2.5k Units Tape and Reel 18 MTC14 LMH6642/6643/6644 Physical Dimensions inches (millimeters) unless otherwise noted 5-Pin SOT23 NS Package Number MF05A Physical Dimensions inches (millimeters) unless otherwise noted 8-Pin SOIC NS Package Number M08A 19 www.national.com LMH6642/6643/6644 Physical Dimensions inches (millimeters) unless otherwise noted 8-Pin MSOP NS Package Number MUA08A www.national.com 20 LMH6642/6643/6644 Physical Dimensions inches (millimeters) unless otherwise noted 14-Pin SOIC NS Package Number M14A 21 www.national.com LMH6642/6643/6644 3V, Low Power, 130MHz, 75mA Rail-to-Rail Output Amplifiers Physical Dimensions inches (millimeters) unless otherwise noted 14-Pin TSSOP NS Package Number MTC14 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. 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