MAX477 300Mhz High-Speed Op

19-0467; Rev 3; 11/99

EVALUATION KIT MANUAL FOLLOWS DATA SHEET 300MHz High-Speed Op Amp

General Description Features MAX477 The MAX477 is a ±5V wide-bandwidth, fast-settling, High Speed unity-gain-stable op amp featuring low noise, low differ- 300MHz -3dB Bandwidth (AV = +1) ential gain and phase errors, high slew rate, high preci- 200MHz Full-Power Bandwidth (AV = +1, VO = 2Vp-p) sion, and high output current. The MAX477’s archi- 1100V/µs Slew Rate tecture uses a standard voltage-feedback topology that 130MHz 0.1dB Gain Flatness can be configured into any desired gain setting, as with other general-purpose op amps. Drives 100pF Capacitive Loads Without Oscillation Unlike high-speed amplifiers using current-mode feed- Low Differential Phase/Gain Error: 0.01¡/0.01% back architectures, the MAX477 has a unique input 8mA Quiescent Current stage that combines the benefits of the voltage-feedback design (flexibility in choice of feedback resistor, Low Input-Referred Voltage Noise: 5nV/√Hz two high-impedance inputs) with those of the current- Low Input-Referred Current Noise: 2pA/√Hz feedback design (high slew rate and full-power band- Low Input Offset Voltage: 0.5mV width). It also has the precision of voltage-feedback amplifiers, characterized by low input-offset voltage 8000V ESD Protection and bias current, low noise, and high common-mode Voltage-Feedback Topology for Simple Design and power-supply rejection. Configurations The MAX477 is ideally suited for driving 50Ω or 75Ω Short-Circuit Protected loads and is available in 8-pin DIP, SO, space-saving µMAX, and 5-pin SOT23 packages. Available in Space-Saving SOT23 Package

Applications Ordering Information

Broadcast and High-Definition TV Systems PIN- TOP PART TEMP. RANGE Video Switching and Routing PACKAGE MARK Communications MAX477EPA -40°C to +85°C 8 Plastic DIP — Medical Imaging MAX477ESA -40°C to +85°C 8 SO — Precision DAC/ADC Buffer MAX477EUA -40°C to +85°C 8 µMAX — MAX477EUK-T -40°C to +85°C 5 SOT23-5 ABYW MAX477MJA -55°C to +125°C 8 CERDIP —

Typical Operating Circuit Pin Configuration

TOP VIEW

VIN MAX477 Ω MAX477 75 V Ω OUT 75 MAX477 OUT 15VCC N.C. 1 8 N.C.

75Ω IN- 2 7 VCC 500Ω 500Ω VEE 2 IN+ 3 6 OUT

V 4 5 N.C. IN+ 34IN- EE

DIP/SO/µMAX VIDEO/RF CABLE DRIVER SOT23-5

______Maxim Integrated Products 1 For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 300MHz High-Speed Op Amp

ABSOLUTE MAXIMUM RATINGS Supply Voltage (VCC to VEE)...... 12V CERDIP (derate 8.00mW/°C above +70°C)...... 640mW Differential Input Voltage...... (VCC + 0.3V) to (VEE - 0.3V) SOT23 (derate 7.1mW/°C above +70°C)...... 571mW Common-Mode Input Voltage...... (VCC + 0.3V) to (VEE - 0.3V) Operating Temperature Ranges Output Short-Circuit Duration to GND...... Continuous MAX477E_A...... -40°C to +85°C Continuous Power Dissipation (TA = +70°C) MAX477EUK ...... -40°C to +85°C Plastic DIP (derate 9.09mW/°C above +70°C)...... 727mW MAX477MJA ...... -55°C to +125°C SO (derate 5.88mW/°C above +70°C)...... 471mW Storage Temperature Range ...... -65°C to +160°C

MAX477 µMAX (derate 4.1mW/°C above +70°C) ...... 330mW Lead Temperature (soldering, 10s) ...... +300°C

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

DC ELECTRICAL CHARACTERISTICS

(VCC = +5V, VEE = -5V, VOUT = 0, RL = ∞, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS MAX477ESA/EPA/EUA/MJA 0.5 2.0 TA = +25°C MAX477EUK 0.5 2.0 Input Offset Voltage VOS mV MAX477ESA/EPA/EUA/MJA TA = TMIN to 3.0 MAX477EUK TMAX 5.0 Input Offset-Voltage Drift TCVOS 2 µV/°C TA = +25°C 13 Input Bias Current IB µA TA = TMIN to TMAX 5.0 TA = +25°C 0.2 1.0 Input Offset Current IOS µA TA = TMIN to TMAX 2.0 Differential-Mode Input R Either input 1 MΩ Resistance IN(DM)

Common-Mode Input Voltage TA = +25°C ±3.0 ±3.5 VCM V Range TA = TMIN to TMAX ±2.5 TA = +25°C VCM = ±3V 70 90 Common-Mode Rejection Ratio CMRR dB TA = TMIN to TMAX VCM = ±2.5V 60 Power-Supply Rejection Ratio PSRR VS = ±4.5V to ±5.5V 70 85 dB

Open-Loop Voltage Gain VOUT = ±2.0V, MAX477E_A/477MJA 55 65 Open-Loop Voltage Gain AVOL dB VCM = 0V, RL = 50Ω MAX477EUK 50 65 TA = +25°C RL = ∞ ±3.5 ±3.9 Output Voltage Swing VOUT RL = 100Ω ±3.0 V TA = TMIN to TMAX RL = 50Ω ±2.5 Minimum Output Current IOUT TA = -40 °C to +85 °C 70 100 mA Short-Circuit Output Current ISC Short to ground 150 mA Open-Loop Output Resistance ROUT VOUT = 0, f = DC 0.1 Ω TA = +25°C 810 mA Quiescent Supply Current ISY MAX477E_ _, TA = TMIN to TMAX 12 mA MAX477MJA, TA = TMIN to TMAX 14

2 ______

MAX477 MAX477-03 Hz Hz √ √ Ω % ns ns pF dB dBc V/µs MHz MHz MHz dBm UNITS nV/ pA/ degrees = +10V/V) VCL 1 2 5 2 36 10 12 2.5 -58 -74 300 130 200 FREQUENCY (Hz) 0.01 0.01 1100 SMALL-SIGNAL GAIN vs. FREQUENCY (A MIN TYP MAX 100k 1M 10M 100M

16 15 14 13 21 20 19 18 17 12 22

GAIN (dB) GAIN MAX477-02 = +25°C, and guaranteed by design over tem- = +25°C, and guaranteed by design over A = +2V/V) to 0.1% to 0.01% VCL = 2Vp-p = 2Vp-p = 2Vp-p CONDITIONS FREQUENCY (Hz) OUT OUT SMALL-SIGNAL GAIN OUT 0.1Vp-p 0.1Vp-p vs. FREQUENCY (A ≤ ≤ = 2Vp-p = ±2Vp-p = 2V step = 2V step 300MHz High-Speed Op Amp High-Speed 300MHz 1M 10M 100M 1G = +25°C, unless otherwise noted.) = +25°C, unless otherwise = 10MHz, V OUT OUT OUT OUT OUT OUT = +25°C, unless otherwise noted.) 2 1 0 5 4 3 7 6 8 c

A -1 -2 f = 5MHz, V f = 10MHz, V V V f = 10MHz f = 10MHz, either input f = 3.58MHz f = 3.58MHz Either input f = 10MHz f V V V V

GAIN (dB) GAIN MAX477-01 = +1, T F n S n -3dB , t = 0pF, T i 0.1dB t e OUT SR DP IP3 DG R THD IN(DM) L t Z VCL SFDR FPBW BW C BW SYMBOL , C , A Ω Ω = +1V/V) VCL = 100 = 100 L L ______3 FREQUENCY (Hz) = -5V, R = -5V, R SMALL-SIGNAL GAIN EE EE vs. FREQUENCY (A PARAMETER perature. an amplitude of 40IRE superimposed on a linear ramp (0 to 100IRE). An IRE is Tested with a 3.58MHz video test signal with by the Institute of Radio Engineers. 140IRE = 1V. a unit of video-signal amplitude developed Specifications for the MAX477EUK (SOT23 package) are 100% tested at T Specifications for the MAX477EUK (SOT23 1M 10M 100M 1G = +5V, V = +5V, V 2 1 0 -6 -7 -8 -3 -4 -5 -1 -2

CC CC Total Harmonic Distortion Spurious-Free Dynamic Range Third-Order Intercept (dB) GAIN Differential-Mode Input Capacitance Output Impedance Input Current Noise Density Differential Gain (Note 2) Differential Phase (Note 2) Rise Time, Fall Time Input Voltage Noise Density Full-Power Bandwidth Full-Power Bandwidth Slew Rate Settling Time Small Signal, ±0.1dB Gain Flatness Small Signal, -3dB Bandwidth Note 2: Note 1: ______Typical Operating Characteristics ______Typical (V AC ELECTRICAL CHARACTERISTICS AC ELECTRICAL (V MAX477 (100mV/div) (50mV/div) VOLTAGE 300MHz High-SpeedOpAmp VOLTAGE (V ______4 GAIN (dB) (2V/div) (1V/div) -0.6 -0.3 -0.2 -0.1 -0.5 -0.4 CC 0.1 0.2 OUT OUT 0 IN IN = +5V,V M1M10 1G 100M 10M 1M SMALL-SIGNAL PULSERESPONSE LARGE-SIGNAL PULSERESPONSE vs. FREQUENCY(A EE GAINFLATNESS (A = -5V,R (A FREQUENCY (Hz) TIME (10ns/div) VCL TIME (10ns/div) VCL =+2V/V) =+2V/V) L VCL = 100 =+1V/V) Ω , C L = 0pF,T GND GND

GND GND MAX477-04 (500mV/div) (50mV/div) VOLTAGE

VOLTAGE GAIN (dB) (200mV/ (2V/div) A Typical OperatingCharacteristics(continued) -6 -2 -1 -5 -4 -3 OUT 0 1 2 3 = +25°C,unlessotherwisenoted.) div) OUT IN IN M1M10 1G 100M 10M 1M LARGE-SIGNAL PULSERESPONSE SMALL-SIGNAL PULSERESPONSE vs. FREQUENCY(A LARGE-SIGNALGAIN (A (A FREQUENCY (Hz) VCL TIME (50ns/div) VCL TIME (50ns/div) =+10V/V) =+10V/V) VCL =+1V/V)

GND GND MAX477-05 GND GND (100mV/div) (100mV/div) VOLTAGE VOLTAGE VOLTAGE (2V/div) OUT OUT OUT IN IN IN SMALL-SIGNAL PULSERESPONSE LARGE-SIGNAL PULSERESPONSE SMALL-SIGNAL PULSERESPONSE (A VCL (A (A =+1V/V,C TIME (10ns/div) VCL TIME (10ns/div) TIME (20ns/div) VCL =+1V/V) =+1V/V) L =50pF) GND GND GND GND GND GND

MAX477 GND GND MAX477-19 5 100 ) B = 100pF)

L MAX477-21 ) TIME (20ns/div) CM = +1V/V, C = 0V TEMPERATURE (˚C) vs. TEMPERATURE 100 CM VCL V INPUT BIAS CURRENT (I (A -25 0 25 50 75 125 C) ˚ LARGE-SIGNAL PULSE RESPONSE -50 0 IN

3.5 3.0 2.5 2.0 1.5 1.0 0.5 OUT (2V/div) (µA) CURRENT BIAS INPUT VOLTAGE TEMPERATURE (

vs. TEMPERATURE MAX477-18 GND GND -25 0 25 50 75 125 ) INPUT COMMON-MODE RANGE (V SY 100 -50

2.8 4.2 3.8 3.6 3.4 3.2 3.0 4.0 COMMON-MODE RANGE (±V) RANGE COMMON-MODE = 50pF) L TIME (20ns/div) TEMPERATURE (˚C) = +1V/V, C vs. TEMPERATURE

VCL (A MAX477-20 -25 0 25 50 75 125 300MHz High-Speed Op Amp High-Speed 300MHz LARGE-SIGNAL PULSE RESPONSE QUIESCENT SUPPLY CURRENT (I -50 100 = +25°C, unless otherwise noted.) = +25°C, unless otherwise 8 6 4 2 0 IN 8 Typical Operating Characteristics (continued) Operating Characteristics Typical 14 12 10 = 50W

OUT L A = 100W

= L R QUIESCENT SUPPLY CURRENT (mA) CURRENT SUPPLY QUIESCENT L R R (2V/div) VOLTAGE

˚ MAX477-17 GND GND = 0pF, T L , C ) Ω 100 TEMPERATURE ( OS vs. TEMPERATURE OUTPUT VOLTAGE SWING C) ˚ = 100 -25 0 25 50 75 125 L = 100pF) L -50 ______

2.5 4.0 3.5 3.0 = -5V, R (±V) SWING VOLTAGE OUTPUT TIME (20ns/div) TEMPERATURE ( = +1V/V, C = 0V vs. TEMPERATURE EE CM VCL V (A INPUT OFFSET VOLTAGE (V -25 0 25 50 75 125 SMALL-SIGNAL PULSE RESPONSE = +5V, V -50 0 IN

CC 400 300 200 100 OUT

-300 -100 -200 (V (µV) VOLTAGE OFFSET INPUT VOLTAGE (100mV/div) MAX477 300MHz High-SpeedOpAmp (V ______6 CC = +5V,V

DISTORTION (dB) POWER-SUPPLY REJECTJION (dB) -100 -110 -100 DIFF PHASE (DEGREES) DIFF GAIN (%) EE -80 -60 -40 -20 -20 -90 -70 -50 -80 -60 -40 -30 -0.002 -0.004 -0.002 -0.004 0.000 0.002 0.004 0.006 0.000 0.002 0.004 0.006 = -5V,R 0 0k1 0 100M 10M 1M 100k 30k k1k1 10M 1M 10k 1k TOTAL HARMONICDISTORTION THIRD HARMONIC 100 0 100 0 DIFFERENTIAL GAINANDPHASE POWER-SUPPLY REJECTION SECOND HARMONIC L HARMONIC DISTORTION (A = 100 VCL vs. FREQUENCY vs. FREQUENCY FREQUENCY (Hz) FREQUENCY (Hz) 0k100M 100k =+1,R Ω , C IRE IRE L L =150 = 0pF,T Ω ) A Typical OperatingCharacteristics(continued) = +25°C,unlessotherwisenoted.)

MAX477-24 MAX477-25 MAX477-22

OUTPUT IMPEDANCE (Ω) DIFF PHASE (DEGREES) DIFF GAIN (%) 100

-0.002 -0.001 -0.012 -0.008 -0.004 OPEN-LOOP GAIN (dB) 0.1 10 0.000 0.001 0.002 0.003 0.000 0.004 1k 1 -10 10 -8 -4 -6 -2 0 4 8 2 6 0k1 0 0M500M 100M 10M 1M 100k 50M GAIN ANDPHASEvs.FREQUENCY 100 0 100 0 DIFFERENTIAL GAINANDPHASE PHASE (A OUTPUT IMPEDANCE VCL vs. FREQUENCY FREQUENCY (Hz) FREQUENCY (Hz) =+2,R OPEN-LOOP 0M500M 100M IRE GAIN IRE L =150 Ω ) MAX477-16

MAX477-23 MAX477-26 -360 -180 0 180 360

PHASE (DEGREES) MAX477 OUT V Setting Gain F R and PC Board Layout and PC Board MAX477 Grounding, Bypassing, Grounding, Bypassing, IN ) V G G Applications InformationApplications R /R F = -(R IN OUT V V Do not use wire-wrap boards. They are too inductive. Do not use wire-wrap boards. They are parasitic capaci- Do not use IC sockets. They increase tance and inductance. have shorter In general, surface-mount components giving better leads and lower parasitic reactance, com- high-frequency performance than through-hole ponents. two layers, with The PC board should have at least a ground plane. one side a signal layer and the other as possible. Keep signal lines as short and straight Do not make 90° turns; round all corners. from voids as The ground plane should be as free possible. Figure 1a. Inverting Gain Configuration The MAX477 can be configured as an inverting or non-The MAX477 can be configured as as any other inverting gain block in the same manner is determined by voltage-feedback op amp. The gain not affect amplifier the ratio of two resistors and does CMF op amps, frequency compensation. This is unlike resistors, typi- which have a limited range of feedback cally one resistor value for each gain and load setting. This is because the -3dB bandwidth of a CMF op amp is set by the feedback and load resistors. Figure 1a shows the inverting gain configuration and its gain To obtain the MAX477’s full 300MHz bandwidth, micro- To obtain the MAX477’s techniques are recommended in strip and stripline the PC board does not degrade most cases. To ensure design the board for a fre- the amplifier’s performance, 1GHz. Even with very short traces, quency greater than at critical points, such as inputs use these techniques you use a constant-impedance and outputs. Whether the following guidelines when board or not, observe designing the board: • • • • • • 300MHz High-Speed Op Amp High-Speed 300MHz Applications FUNCTION High-Performance Amplifier Output Positive Power Supply No Connect. Not inter- nally connected. Inverting Input Noninverting Input Negative Power Supply in the EE CC IN- V IN+ N.C. V OUT NAME Detailed Description 1 5 4 3 2 — ______7 SOT23 Output Short-Circuit Protection section. 3 4 6 7 2 PIN 1, 5, 8 SO/µMAX/DIP ______Pin Description ______Pin Video Distribution Amplifier Information Under short-circuit conditions, the output current is typi- cally limited to 150mA. This is low enough that a short to ground of any duration will not cause permanent damage to the chip. However, a short to either supply will significantly increase the power dissipation and may cause permanent damage. The high output- current capability is an advantage in systems that trans- mit a signal to several loads. See The MAX477 allows the flexibility and ease of a classic The MAX477 allows the flexibility and maintaining the voltage-feedback architecture while feedback (CMF) high-speed benefits of current-mode a voltage-feedback amplifiers. Although the MAX477 is an 1100V/µs op amp, its internal architecture provides CMF ampli- slew rate and a low 8mA supply current. low supply fiers offer high slew rates while maintaining resistors as part current, but use the feedback and load network. In of the amplifier’s frequency compensation with high imped- addition, they have only one input ance. specifications like The MAX477 has speed and power but has high input those of current-feedback amplifiers, Like other voltage- impedance at both input terminals. compensation is feedback op amps, its frequency resistors, and it independent of the feedback and load product. However, exhibits a constant gain-bandwidth unlike standard voltage-feedback amplifiers, its large- signal slew rate is not limited by an internal current source, so the MAX477 exhibits a very high full-power bandwidth. MAX477 300MHz High-SpeedOpAmp done intheusualway.Thefollowinganalysisshows MAX477 allowsDCerrorandnoisecalculationstobe The standardvoltage-feedbacktopologyofthe bandwidth forseveralgainvalues. recommended resistorcombinationsandmeasured and causeoscillations(Figure2).Table1showsthe by R excess phaseresultingfromthepolefrequencyformed In eithertheinvertingornoninvertingconfiguration, The MAX477’sinputcapacitanceisapproximately1pF. capacitance. lack ofleadsalsominimizeparasiticinductanceand linear mannerusingathickfilm.Theirsmallsizeand tors, buttominimizeinductance,itisdepositedinaflat, cuits. Theirmaterialissimilartothatofmetal-filmresis- Surface-mount resistorsarebestforhigh-frequencycir- select resistorsthataresmallandnoninductive. with current-feedbackamplifiers).However,besureto in theinvertingornoninvertinggainconfigurations(as The feedbackandinputresistorvaluesarenotcritical configuration. equation, whileFigure1bshowsthenoninvertinggain Parasitic CapacitanceonBandwidth Figure 2.EffectofHigh-Feedback ResistorValuesand Figure 1b.NoninvertingGainConfiguration ______8 f || V IN R V g OUT and Ccandegradeamplifierphasemargin =[1+(R R G R G F /R C G V )] V IN IN MAX477 Choosing ResistorValues MAX477 DC andNoiseErrors R R F F R L V V OUT OUT )InFigure3,totaloutputoffseterrorisgivenby: 1) errors andlowernoisecomparedtoCMFamplifiers. vides aprecisionamplifierwithsignificantlylowerDC that theMAX477’svoltage-feedbackarchitecturepro- hr e where MAX477’s totalinput-referrednoiseinaclosed- The 2) Various Closed-LoopGainConfigurations Table 1.ResistorandBandwidthValuesfor V=1+ – OUT necessitate theuseoflow-valueresistorsforR tice, high-speedconfigurationsfortheMAX477 drops outoftheequationfortotalDCerror.Inprac- and Rg.Inthiscase,theV For thespecialcaseinwhichR loop feedbackconfigurationcanbecalculatedby: DC errorsource. equal toR for I GAIN (V/V) +10 -10 +5 +2 +1 -5 -2 -1 e R i OS n        R n EQ RIRIRRR R I IR IRR V SBSBfgO g f S OS g f B S B OS (R eeeiR = input-referred noisecurrentofthe = input-referred noisevoltageofthe = totalequivalentsourceresistanceat = R R TnRnEQ S f + g f =++ the twoinputs,i.e.,R resistor noisevoltagedueto R MAX477 (2pA MAX477 (5nV || + (R    

Rg, theI Open = 4KT R = e 100 150 300 125 500 ( R     50 50 f Ω REQ g || ) 22   Rg) <

IN V (dB) GAIN Figure 4. Effect of C Figure 3. Output Offset Voltage Figure 3. Output Offset of the amplifier itself is much higher. Note that adding an isolation resistor degrades gain accuracy. The load and isolation resistor form a divider that decreases the voltage delivered to the load. The MAX477 drives capacitive loads up to 100pF with- The MAX477 drives capacitive loads (in the frequen- out oscillation. However, some peaking cy domain) or ringing (in the time domain) may occur. This is shown in Figure 4 and in the Small and Large- Signal Pulse Response graphs in the Characteristics To drive larger-capacitance loads or to reduce ringing, add an isolation resistor between the amplifier’s output and the load, as shown in Figure 5. The value of R capacitive load. Figure 6 shows the Bode plots that result when a 20 age follower driving a range of capacitive loads. At the higher capacitor values, the bandwidth is dominated by the RC network, formed by R . Ω RMS = 500 300MHz High-Speed Op Amp High-Speed 300MHz µ g , and assum- = = z = R H f √ , R     Ω cable). However, the f g ) and input noise volt- 471 239 R R Ω OS = 5.5nV = 75 , multiplied by the gain , multiplied by the x MHz V T = ()

    T S    + Driving Capacitive Loads 500 500 + || 1    ______9 () OUT T e = e1+ e = + 22 2 ()

ΩΩΩΩ 523232555 4 325 2 3 25 () ). For a current-mode feedback amplifier with ). For a current-mode feedback amplifier 75 500 500 325 n == +° = =+ ./ . . OUT input-referred noise, e input-referred noise, factor: T EQ R e = x 5.5nV e nV nV pA x nV Hz e KT x nV Hz at C R Note that for both DC and noise calculations, errors are Note that for both DC and noise calculations, As an example, consider R As an example, consider offset and noise errors significantly higher, the calcula- offset and noise errors significantly tions are very different. dominated by offset voltage (V ing a signal bandwidth of 300MHz (471MHz noise ing a signal bandwidth of 300MHz bandwidth is: bandwidth), total output noise in this The MAX477 provides maximum AC performance with The MAX477 provides maximum AC the case when the no output load capacitance. This is transmission MAX477 is driving a correctly terminated line (i.e., a back-terminated 75 MAX477 is capable of driving capacitive loads up to 100pF without oscillations, but with reduced AC performance. Driving large capacitive loads increases the chance of oscillations in most amplifier circuits. This is especially true for circuits with high loop gain, such as voltage fol- lowers. The amplifier’s output resistance and the load capacitor combine to add a pole and excess phase to the loop response. If the frequency of this pole is low enough and phase margin is degraded sufficiently, oscillations may occur. A second problem when driving capacitive loads results from the amplifier’s output impedance, which looks inductive at high frequency. This inductance forms an L-C resonant circuit with the capacitive load, which causes peaking in the frequency response and degrades the amplifier’s gain margin. 3) is simply total MAX477’s output-referred noise The Then: age (e In the above example, with e MAX477 and a1.2GHzinputbandwidth. ADCs. BothoftheseADCshavea50 250Msps MAX100andthe500MspsMAX101flash Figure 7showsapreampfordigitizingvideo,usingthe drive theinputsofADCwhilemaintainingaccuracy. ADC. Withitslowoutputimpedance,theMAX477can ing thelow-impedanceinputofahigh-speedflash to drivecapacitiveloadsmakeitwellsuitedforbuffer- The MAX477’shighoutput-drivecapabilityandability 300MHz High-SpeedOpAmp Figure 7.PreampforVideoDigitizer Figure 6.EffectofC Figure 5.Capacitive-LoadDrivingCircuit Isolation Resistor 0______10 V IN 500 VIDEO IN

Ω GAIN (dB) -6 -5 -4 -3 -2 -1 0 1 MAX477 M1M10 1G 100M 10M 1M R LOAD ISO MAX477 =20W 500 on FrequencyResponsewith Ω FREQUENCY (Hz) C C L =22pF L C =100pF L =47pF Flash ADCPreamp R ISO C L Ω C (MAX100/MAX101) input resistance L =0pF FLASH ADC R L V OUT Bessel filter. delay inthepassband,whichischaracteristicof filter’s frequencyresponseanddelay.Noticetheflat square-wave pulseresponse,andFigure10bshowsthe width of10MHz,anda28nsdelay.Figure10ashows nent valuesarechosenforagainof+2,-3dBband- filter usingamultiplefeedbacktopology.Thecompo- Figure 9showsawide-bandwidth,second-orderBessel ues canbechosenindependentlyofopampbias. design isstraightforwardbecausethecomponentval- used inallstandardactivefiltertopologies.The Two high-impedanceinputsallowtheMAX477tobe the attachmentofuptosix±2Vp-p,150 cables (Figure8).Thehighoutput-currentdriveallows excellent driverforback-terminated75 In againof+2configuration,theMAX477makesan the MAX496/MAX497datasheet. gain-of-2 videolinedriversinasinglepackage,referto need forexternalgain-settingresistors.Formultiple similar amplifierconfiguredforagainof+2withoutthe the numberofloadsmaydouble.TheMAX4278isa MAX477 at+25°C.Withtheoutputlimitedto±1Vp-p, Figure 8.High-PerformanceVideo DistributionAmplifier VIDEO IN 500 Ω MAX477 500 Wide-Bandwidth BesselFilter Ω High-Performance Video Distribution Amplifier 75 75 75 Ω Ω Ω 75 75 75 Ω Ω Ω Ω Ω video coaxial loads tothe 75 75 75 Ω Ω Ω OUTN OUT2 OUT1 MAX477 EE ______Chip Information______Chip TRANSISTOR COUNT: 175 TRANSISTOR COUNT: TO V SUBSTRATE CONNECTED

OUT

V DELAY (ns) DELAY 300MHz High-Speed Op Amp High-Speed 300MHz GND GND -42 -32 -22 -52 -12 48 38 28 18 8 -2 GAIN DELAY MAX477 20pF TIME (50ns/div) FREQUENCY (MHz) Ω Ω ______11 110 100pF 602 IN 1M 10M 100M OUT 0.2V -0.2V Ω 8 6 4 2 0

-2 -4 -6 -8 10

-10 301 (100mV/div) (dB) GAIN (200mV/div) VOLTAGE (V) IN V Figure 10b. Gain and Delay vs. Frequency Figure 10a. 5MHz Square Wave Input Figure 9. 8MHz Bessel Filter MAX477 300MHz High-SpeedOpAmp 2______12 ______Package Information

SOT5L.EPS 8LUMAXD.EPS