LH4001 Wideband Current Buffer General Description Features The LH4001 is a high speed unity gain buffer designed to provide high current drive capability at frequencies from DC to over 25 MHz. It is capable of providing a continuous output current of g 100 mA and a peak of g 200 mA. The LH4001 is designed to fulfill a wide range of applications such as impedance transformation, high impedance input buffers for A/D converters and comparators, as well as high speed line drivers. It is also suitable for use in current booster applications within an op amp loop. This allows the output current capability of existing op amps to be increased to g 100 mA. Y Y Y Y Y DC to 25 MHz bandwidth 125 V/ms slew rate Drives g 10V into 50X Operates from g 5 to g 20V supplies Output swing approaches supply voltage Applications Y Y Y Y Boost op amp output Buffer amplifiers Isolate capacitive loads Drive long cables Typical Applications and Connection Diagram TL/K/8628 – 1 Dual-In-Line Package TL/K/8628 – 2 Top View *Note: Electrically connected internally. No connection should be made to these pins. Order Number LH4001CN See NS Package Number N10A C1995 National Semiconductor Corporation TL/K/8628 RRD-B30M115/Printed in U. S. A. LH4001 Wideband Current Buffer February 1995 Absolute Maximum Ratings Storage Temperature Range, TSTG Junction Temperature, TJ Lead Temp. (Soldering, k10 seconds) ESD rating is to be determined. If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/Distributors for availability and specifications. Supply Voltage, VS Continuous Output Current, IO Peak Output Current, IO(peak) (50 ms On/1 Sec Off) Input Voltage Range, VIN Power Dissipation g 22V b 65§ C to a 150§ C 150§ C 260§ C g 100 mA Operating Ratings g 200 mA Temperature Range, TA Thermal Resistance iJA g VS 0§ C to a 70§ C 120§ C/W 500 mW Electrical Characteristics (Note 1) Symbol Min Typ Max Units Voltage Gain RS e 10 kX, RL e 1 kX VIN e g 10V 0.95 0.97 1 V/V RIN Input Impedance RS e 200 kX, RL e 1 kX VIN e g 1.0V 180 400 ROUT Output Impedance RS e 10 kX, RL e 50X VIN e g 1.0V VO Output Swing VS e g 15V, RS e 50X RL e 100X, VIN e g 12V IB Input Bias Current RS e 10 kX, RL e 1 kX tr Rise Time RL e 100X, DVIN e 100 mV SR Slew Rate VIN e g 5V, RL e 100X IS Supply Current RS e 10 kX VOS Offset Voltage RS e 300X, RL e 1 kX AV Parameter Conditions 6 g 10 kX 10 g 11 g 10 X V g 50 mA 7 ns 125 V/ms g6 g 10 mA g 10 g 50 mV Note 1: Specification applies for TA e 25§ C with a 12V on Pins 1 & 2; b 12V on Pins 4 & 5 unless otherwise specified. Typical Performance Characteristics Input Offset Current Frequency Response Supply Current TL/K/8628 – 3 Pulse Response TL/K/8628 – 10 VIN e g 2.5V, RS e RL e 50X 2 Applications Information Figure 1 shows a simple implementation of a non-inverting buffer amplifier of unity gain. Popular industry standard operational amplifiers such as LF156, LF351, LF411, LF441, LM11, LM741, etc. can be used in this configuration. Due to the high bandwidth of the LH4001, it is suitable for use with most monolithic op amps. Figure 2 shows an implementation of an inverting amplifier with output current capability in excess of g 100 mA. The gain of this amplifier is determined by the values of RF and RIN. The resistor between the non-inverting input and ground is used to minimize the output offset voltage resulting from the input bias current. Because of its high current drive capability, the LH4001 buffer amplifier is suitable for driving terminated or unterminated co-axial cables, and high current or reactive loads. Figure 3 shows a co-axial cable drive circuit. The 43X resistor matches the driving source to the cable, however, its inclusion rarely will result in substantial improvement in pulse response into a terminated cable. If the 43X resistor is included, the output voltage to the load is about half what it would be without the near end termination. Figure 4 shows a non-inverting amplifier with gain and output current capability in excess of g 100 mA. It is capable of providing g 10 mA into a 1 kX load or g 100 mA into a 100X load ( g 10V swing). Figures 5 and 6 show two different methods of providing current limit or short circuit protection for the LH4001. In Figure 6, the 10X resistor limits the output current to approximately 70 mA. This circuit is highly recommended if there is a potential for a short circuit to occur. TL/K/8628 – 4 FIGURE 1. Non-Inverting Buffer Amplifier VOUT R eb F VIN RIN TL/K/8628 – 6 FIGURE 2. Inverting Buffer Amplifier with Current Limit 3 Applications Information (Continued) RLIM e 100X, 1W TL/K/8628 – 7 FIGURE 3. Coaxial Cable Drive Circuit TL/K/8628 – 5 VOUT e VIN # 1a R2 R1 J FIGURE 4. Non-Inverting Buffer Amplifier with Gain TL/K/8628 – 8 FIGURE 5. LH4001 Using Resistor Current Limiting Q1, Q2 e 2N2905 Q3, Q4 e 2N2219 TL/K/8628 – 9 FIGURE 6. Current Limit Using Current Sources 4 5 LH4001 Wideband Current Buffer Physical Dimensions inches (millimeters) Lit. Ý106408 Molded Dual-in-Line Package (N) Order Number LH4001CN NS Package Number N10A 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 OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. 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