Dual, High Output, Programmable Gain Buffer# Technical Datasheet: LMH6718MA High-Speed Operational Amplifier
Manufacturer : National Semiconductor (NS)
Document Version : 1.0
Date : October 26, 2023
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## 1. Application Scenarios
The LMH6718MA is a high-speed, voltage-feedback operational amplifier designed for applications requiring wide bandwidth, low distortion, and fast settling time. Its architecture makes it suitable for both DC precision and AC performance-critical circuits.
### Typical Use Cases
* Video Signal Processing: The amplifier's 400 MHz large-signal bandwidth and 0.02% / 0.02° differential gain/phase error make it ideal for driving 75Ω video lines, RGB amplifiers, and HDTV component video buffers.
* High-Speed Data Acquisition Front-Ends: Its fast settling time (10 ns to 0.1% for a 2V step) is critical for sample-and-hold circuits and the input buffers of high-speed analog-to-digital converters (ADCs) in oscilloscopes and communication systems.
* Active Filters & Equalizers: The wide unity-gain bandwidth allows for the implementation of high-frequency active filters (e.g., Sallen-Key topology) for signal conditioning in disk drives and RF intermediate frequency (IF) stages.
* Pulse Amplification: With a high slew rate (3100 V/µs), it is well-suited for amplifying and shaping fast digital pulses in test equipment and laser diode drivers.
* Differential Line Drivers: When used in pairs, it can effectively drive differential lines for standards like LVDS in professional video and high-speed digital interfaces.
### Industry Applications
* Professional Broadcast & AV Equipment: For distribution amplifiers, switchers, and production gear requiring transparent signal integrity.
* Test & Measurement: Used in the analog signal path of high-bandwidth oscilloscopes, arbitrary waveform generators, and spectrum analyzers.
* Medical Imaging: In ultrasound and other imaging systems where high-fidelity analog front-ends are necessary.
* Communications Infrastructure: IF strip amplification and filtering in wireless base stations and microwave backhaul systems.
### Practical Advantages and Limitations
Advantages:
* Excellent Speed-Power Ratio: Provides high bandwidth and slew rate while maintaining a moderate quiescent current (10.5 mA typical).
* High Output Drive: Capable of driving heavy capacitive loads (up to 100 pF) and resistive loads as low as 100Ω while maintaining stability, which is uncommon for many high-speed op-amps.
* Disable Function: The `SHDN` (shutdown) pin allows the amplifier to be placed in a low-power standby mode (~1.5 mA), useful for power-sensitive or multiplexed applications.
* Good DC Performance: Low input offset voltage (1 mV max) and high open-loop gain (80 dB min) allow for use in DC-coupled applications.
Limitations:
* Voltage Noise: At 4.3 nV/√Hz, the voltage noise density is higher than some precision, lower-bandwidth amplifiers. This may limit its use in very low-noise, high-gain preamplifier stages for sensitive sensors.
* Power Supply Range: Operates on ±5V supplies (10V total). It is not a single-supply or low-voltage (e.g., 3.3V) part, which may limit its use in modern mixed-signal systems without appropriate power rails.
* Thermal Considerations: In high-frequency, high-output drive applications, the SOIC-8 package has a θJA of 160°C/W. Care must be taken to manage power dissipation to avoid thermal shutdown or performance degradation.
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## 2. Design Considerations
### Common Design Pitfalls and Solutions
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