19-0315; Rev 0; 10/94 950MHz FET-Input Buffer with 75Ω Output The MAX4005 is a ±5V, single-ended unity-gain buffer with a high-impedance JFET input, intended to drive a 75Ω load. A 75Ω thin-film output resistor is included onboard to minimize reflections when driving a 75Ω load through a transmission line of arbitrary length. Gain in this configuration is 0.5. ____________________________Features ♦ 950MHz Bandwidth ♦ 350ps Rise/Fall Times ♦ 0.11%/0.03° Differential Gain/Phase Error ♦ 1000V/µs Slew Rate ♦ 10pA Input Bias Current ♦ 75Ω Output Impedance ________________________Applications Video Buffer / Line Driver Isolation Between High-Impedance Node and Low-Impedance Instrument ______________Ordering Information Remote Signal Sensing Impedance Transformation Fanout Multiplier for 75Ω Distribution Systems __________Typical Operating Circuit PART TEMP. RANGE MAX4005CSA 0°C to +70°C PIN-PACKAGE 8 SO __________________Pin Configuration TOP VIEW -5V 8 1 MAX4005 INPUT +5V 2 7 3 6 4 5 -5V N.C. Z = 75Ω +5V OUT RL = 75Ω VEE 1 8 VEE IN 2 7 PEAK 6 OUT 5 VCCO GND 3 MAX4005 VCC 4 SO ________________________________________________________________ Maxim Integrated Products Call toll free 1-800-998-8800 for free samples or literature. 1 MAX4005 _______________General Description MAX4005 950MHz FET-Input Buffer with 75Ω Output ABSOLUTE MAXIMUM RATINGS Input Voltage.......................................................................±2.5V VCC Supply Voltage ............................................................+5.5V Output-Stage Supply .........................................................+5.5V VEE Supply Voltage..............................................................-5.5V Peaking Pad Voltage.............................................................0.0V Ground Voltage .....................................................................0.0V Continuous Power Dissipation (TA = +70°C) ...................471mW Operating Temperature Range...............................0°C to +70°C Lead Temperature (soldering, 10sec) .............................+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. ELECTRICAL CHARACTERISTICS (VCC = 4.75V to 5.25V, VEE = -4.75V to -5.25V, TA = +25°C, stated performance characterized for TA = 0°C to +70°C, unless otherwise noted.) MIN TYP MAX UNITS +5V VCC Current PARAMETER IVCC1 VIN = 0V, RL = 75Ω 9 14 19 mA +5V Output Stage Quiescent Current IVCC2 VIN = 0V, RL = 75Ω 9 11 14 mA IVEE VIN = 0V, RL = 75Ω 17 24 31 mA RL = 75Ω, gain = 0.5 -3 3 mV 76.5 Ω nA -5V VEE Current SYMBOL Output Offset Voltage Output Resistance Input Current CONDITIONS ROUT IB 74.0 75.0 VIN = 0V -1 0.01 1 Gain RL = 75Ω 0.49 0.50 0.51 Linearity RL = 75Ω, measured over input dynamic range 0.50 1 % Input Dynamic Range +5V VCC Power-Supply Rejection Ratio RL = 75Ω, gain = 0.5 VIN = 0V, RL = 75Ω 1.6 +5V Output Stage Power-Supply Rejection Ratio -5V VEE Power-Supply Rejection Ratio -1.3 40 55 V dB VIN = 0V, RL = 75Ω 50 75 dB VIN = 0V, RL = 75Ω 40 60 dB TYPICAL OPERATING PERFORMANCE (VCC = 5.0V, VEE = -5.0V, RL = 75Ω, TA = +25°C, unless otherwise noted.) -3dB 950 Bandwidth BW -6dB 2000 Input Capacitance Settling Time to 0.1% Rise/Fall Times CIN tSET 2.2 VIN = 0.25V step, VOUT = 0.125V step tRISE/tFALL VIN = 0.25V step with < 30ps rise time pF 2 ns 350 ps ±0.01 dB Gain Flatness GF Gain Flatness ±0.1dB GF1 60 MHz Gain Flatness ±0.2dB GF2 80 MHz 1000 V/µs Slew Rate At 30MHz MHz SR VIN = 2.5V step with 200ps rise time Overdrive Recovery Time tOD VIN = 2.5V step 5 ns 2nd Harmonic Distortion 2HD At 50MHz -50 dBc 3rd Harmonic Distortion 3HD At 50MHz < -60 dBc 3rd-Order Intercept TOI At 100MHz 28 dBm Differential Gain Error DG At 3.58MHz 0.11 % Differential Phase Error DP At 3.58MHz 0.03 degrees 2 _______________________________________________________________________________________ 950MHz FET-Input Buffer with 75Ω Output SMALL-SIGNAL STEP RESPONSE OUTPUT VOLTAGE (10mV/div) VOLTAGE GAIN (5dB/div) 10 100 tRISE = 340ps 1000 MAX4005-03 OUTPUT VOLTAGE (20mV/div) MAX4005-01 -3dB, 977MHz -6dB 0.3 1 SMALL-SIGNAL STEP RESPONSE MAX4005-02 GAIN vs. FREQUENCY tRISE = 357ps TIME (2ns/div) TIME (2ns/div) FREQUENCY (kHz) THIRD-ORDER INTERCEPT vs. FREQUENCY CL = 5.6pF CL = 10pF CL = 18pF CL = 33pF VIN = 200mV STEP RL = 75Ω MAX4005-05 40 THIRD-ORDER INTERCEPT (dBm) OUTPUT VOLTAGE (20mV/div) MAX4005-04 SMALL-SIGNAL STEP RESPONSE vs. CAPACITIVE LOAD 35 30 25 20 15 10 5 0 TIME (2ns/div) 100 150 200 250 300 350 400 FREQUENCY (MHz) _______________________________________________________________________________________ 3 MAX4005 __________________________________________Typical Operating Characteristics (TA = +25°C, unless otherwise noted.) MAX4005 950MHz FET-Input Buffer with 75Ω Output _____________________Pin Description PIN NAME FUNCTION 1, 8 VEE -5V Negative Supplies 2 IN High-Impedance Input 3 GND Ground 4 VCC +5V Positive Supply 5 VCCO Output Stage +5V Positive Supply 6 OUT Output (ZOUT = 75Ω) 7 PEAK Normally no connection. Capacitor to ground will peak frequency response. __________Applications Information Power Supply The MAX4005 allows for two separate +5V supplies for the output stage and the rest of the MAX4005 circuit. The supplies are bonded out separately to give the option of using a different +5V supply. The output stage is a Class A type, with the output transistor fed by a current source in the emitter, so its current will vary with output signal. For best bandwidth and pulse response, solder bypass chip capacitors directly from the supply pins on the four corners of the package to a ground plane. Input Impedance The MAX4005 has a JFET input with an input capacitance of only 2pF. As a result, the leakage current is typically less than 10pA. This exceptionally high input impedance is important in applications that require isolation between a high source impedance and a lowimpedance transmission cable. An attenuator may be used in front of the MAX4005 to increase the dynamic range and reduce input capacitance. Output Impedance A 75Ω precision thin-film output resistor is included onboard to provide more precise reverse termination than standard discrete resistors. This minimizes reflections caused by impedance mismatching when driving transmission cable. The MAX4005 can also drive a 50Ω load with only a slight loss in amplitude (gain drops from 0.5 to 0.4). The typical operating performance specifications shown in the Electrical Characteristics have been verified with a 50Ω load, as well as a 75Ω load. Frequency Response Peaking To peak the response to compensate for losses when driving long transmission lines, connect a chip capacitor of about 10pF to 50pF between the PEAK pin and ground. This peaking occurs in the 200MHz to 500MHz range. The PEAK pin will normally be left open for flattest response. Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. 4 ___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 © 1994 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.