Texas Instruments LMH6550MAX

Overview

LMH6550MAX from Texas Instruments is a high-speed, fully differential voltage-feedback operational amplifier optimized for driving high-performance ADCs and balanced transmission lines. It delivers 400 MHz −3-dB bandwidth (V_OUT = 0.5 V_PP), 3000 V/µs slew rate, and −92/−103 dB HD2/HD3 at 5 MHz under ±5 V supply - enabling precision differential signaling in IF/RF, video-over-twisted-pair, and single-ended-to-differential conversion applications.

For engineers reviewing the LMH6550MAX datasheet, LMH6550MAX pinout, LMH6550MAX application, or LMH6550MAX equivalent, key selection considerations include its differential I/O architecture with integrated common-mode feedback, enable-controlled power-down (10 ns toggle), V_CM-settable output common-mode voltage, and SOIC-8 package compatibility with standard PCB layouts for high-frequency analog signal chains.

Technical Context

The LMH6550MAX implements a three-channel functional architecture: two high-gain, inverting-mode differential signal paths (V₊/V₋) and a dedicated common-mode feedback loop that senses output average voltage and compares it to the V_CM pin reference. This enables precise control of output common-mode level and maintains amplitude/phase balance even with single-ended input drive.

It operates as a voltage-feedback amplifier requiring external gain-setting resistors (e.g., R_F = R_G = 365 Ω for unity gain). The V_CM pin accepts an external reference (or floats to midsupply via internal 50-kΩ dividers) and must be bypassed with 0.1-µF ceramic capacitor to suppress noise coupling into the output common-mode path.

Key Specifications

Pinout & Package

LMH6550MAX is housed in an 8-pin SOIC package (4.90 mm × 3.91 mm body size), optimized for thermal performance and high-frequency layout with short internal trace lengths.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar differential amplifier applications.

Compared with THS4561DR and ADA4940-1ARZ, the LMH6550MAX offers the highest small-signal bandwidth and slew rate among the three, making it uniquely suitable for wideband IF/RF signal chains demanding both speed and linearity - especially where 400 MHz operation and 3000 V/µs transient response are critical.

Availability

LMH6550MAX is available at Aetrix Electronics and suitable for high-speed data acquisition, video-over-cable, IF/RF signal conditioning, and single-ended-to-differential conversion requiring stable component supply and long-term industrial availability.

Supply support for LMH6550MAX includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor leader specializing in analog and embedded processing technologies, with decades of expertise in high-speed amplifiers and data converter interfaces.

The LMH6550MAX belongs to TI's high-speed differential amplifier product line, engineered specifically for precision, wideband signal conditioning in ADC driver, communications, and video infrastructure applications.

FAQ

What is the recommended supply voltage range for stable operation of the LMH6550MAX?

The LMH6550MAX operates reliably across a total supply voltage range of 4.5 V to 12 V, supporting both split-rail (e.g., ±5 V) and single-supply (e.g., 5 V with V_CM = 2.5 V) configurations. At ±5 V, it achieves full 400 MHz bandwidth and −103 dBc HD3 at 5 MHz. Operation below ±2.25 V per rail risks degraded slew rate and bandwidth; above ±6 V exceeds absolute maximum ratings.

How does the V_CM pin function in the LMH6550MAX, and what happens if left unconnected?

The V_CM pin on the LMH6550MAX sets the output common-mode voltage via an internal error amplifier. If left floating, it defaults to midsupply (e.g., 0 V with ±5 V supplies) using internal 50-kΩ resistive dividers. However, TI strongly recommends bypassing this high-impedance node with a 0.1-µF ceramic capacitor to ground - unfiltered V_CM introduces noise directly into the output common-mode path, degrading dynamic range and balance error.

Can the LMH6550MAX drive a 50-Ω differential load directly, and what external components are required?

Yes, the LMH6550MAX can drive a 50-Ω differential load directly, delivering up to 7.8 V_PP swing and ±75 mA linear output current. To ensure stability and optimal distortion performance, external gain-setting resistors (e.g., R_F = R_G = 365 Ω for unity gain) and series output resistors (R_O ≈ 10–22 Ω per leg) are required. These R_O resistors isolate the amplifier from capacitive loads like ADC input capacitance or cable termination.

What is the purpose of the EN pin on the LMH6550MAX, and how does it affect output behavior during disable?

The EN pin on the LMH6550MAX controls power-down mode: logic high (>2.0 V) enables normal operation; logic low (<1.5 V) reduces quiescent current to 1.2 mA. During disable, the output stage enters high-impedance state - but the external feedback and gain resistors remain connected, so input-to-output isolation is poor. Signal sources may couple through R_F/R_G networks, making EN unsuitable for true signal blocking without additional switching.

How does the LMH6550MAX achieve single-ended-to-differential conversion without external transformers or baluns?

The LMH6550MAX achieves active single-ended-to-differential conversion using its integrated common-mode feedback architecture. With only IN+ driven and IN− grounded (or biased), the V_CM loop forces −OUT to mirror +OUT in amplitude while maintaining opposite polarity. This eliminates the need for passive baluns, reduces size/cost, and avoids transformer bandwidth limitations - enabling flat response from DC to 400 MHz in compact PCB layouts.