270MHz Single Supply, Single & Dual Operational Amplifiers# Technical Documentation: LMH6658MMX High-Speed Operational Amplifier
Manufacturer : National Semiconductor Corporation (NSC)
Component : LMH6658MMX (Dual, High-Speed, Voltage Feedback Op-Amp)
Package : 8-Pin VSSOP (MMX)
Document Revision : 1.0
Date : October 2023
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## 1. Application Scenarios
### 1.1 Typical Use Cases
The LMH6658MMX is a dual, high-speed voltage-feedback operational amplifier optimized for applications requiring wide bandwidth, fast settling, and low distortion. Its design centers on a unity-gain stable architecture with a gain-bandwidth product (GBW) of 400 MHz and a slew rate of 1600 V/µs.
* Active Filtering : Ideal for high-frequency active filters (e.g., Sallen-Key, Multiple Feedback topologies) in signal conditioning paths, such as anti-aliasing filters for high-speed ADCs or reconstruction filters for DACs. Its bandwidth supports filter cut-off frequencies well into the tens of MHz.
* ADC/DAC Buffering : Serves as an excellent buffer or driver for high-speed data converters (10-14 bit ADCs, sampling at 50+ MSPS). Its low harmonic distortion and fast settling time minimize signal integrity loss during acquisition.
* Video Signal Processing : Suitable for SD/HD video distribution, switching, and line driving due to its high slew rate and differential gain/phase performance, ensuring minimal signal degradation.
* Test & Measurement Equipment : Used in the front-end amplification stages of oscilloscope probes, arbitrary waveform generators, and spectrum analyzers where signal fidelity and wide bandwidth are critical.
* Transimpedance Amplification (TIA) : Can be configured for moderate-bandwidth photodiode amplification in optical communication receivers, though its voltage-noise density should be evaluated against the specific photodiode capacitance.
### 1.2 Industry Applications
* Communications Infrastructure : IF/RF signal chain amplification in software-defined radios (SDR), base transceiver stations, and radar systems.
* Medical Imaging : Ultrasound pre-amplification and signal conditioning channels where high slew rate and bandwidth are needed for accurate pulse echo reception.
* Professional Audio/Video : High-end broadcast equipment, video routers, and professional audio mixing consoles for clean signal amplification and routing.
* Automated Test Equipment (ATE) : Pin electronics and parametric measurement units requiring precise, fast analog stimulus and response.
### 1.3 Practical Advantages and Limitations
Advantages:
* High Speed : 400 MHz GBW and 1600 V/µs slew rate enable processing of fast-edged signals.
* Low Distortion : Excellent harmonic distortion performance (e.g., -80 dBc SFDR at 5 MHz) preserves signal purity.
* Rail-to-Rail Output (RRO) : Maximizes dynamic range when operating on low supply voltages (as low as ±2.5V).
* Dual Configuration : Saves board space and power in multi-channel systems compared to two single op-amps.
* Good DC Performance : Low input offset voltage (typ. 1 mV) and bias current simplify DC-coupled designs.
Limitations:
* Not Rail-to-Rail Input (RRI) : The input common-mode voltage range extends to within approximately 2V of the supply rails. This restricts its use in very low-voltage, single-supply applications where the signal nears ground.
* Moderate Power Consumption : With a typical supply current of 6.5 mA per amplifier, power-sensitive portable/battery-operated designs may require evaluation against lower-power alternatives.
* Stability Considerations : Like all high-speed voltage-feedback amps, it
