Texas Instruments OPA628AU

Overview

OPA628AU from Burr-Brown (now Texas Instruments) is a unity-gain-stable, voltage-feedback operational amplifier optimized for broadcast-quality video and precision wideband signal conditioning. It delivers 0.015% differential gain error, 0.015° differential phase error at NTSC/PAL frequencies, 90dB spurious-free dynamic range (SFDR), 160MHz unity-gain bandwidth, and 2.5nV/√Hz input voltage noise - enabling high-fidelity analog front-ends in medical imaging and ADC/DAC buffering.

For engineers reviewing the OPA628AU datasheet, OPA628AU pinout, OPA628AU application, or OPA628AU equivalent, this page provides verified technical context, validated pin functions, real-world application constraints (e.g., ±5V dual supply, 8-pin SOIC package, –40°C to +85°C operation), and confirmed alternative options for low-distortion wideband op amp selection.

Technical Context

The OPA628AU employs a multistage voltage-feedback architecture with fully symmetrical differential inputs, laser-trimmed thin-film resistors for DC/AC parameter optimization, and separate input/output stage power supplies (±VCC, Input; ±VCC, Output) to suppress package parasitic coupling. Its 60° phase margin ensures unity-gain stability while maintaining 30MHz 0.1dB gain flatness at G = +2.

Distortion performance is achieved via high open-loop gain and layout-aware compensation: harmonic distortion reaches –98dBc (3rd harmonic, 5MHz, RL = 100Ω, G = +1), two-tone third-order intercept is 60dBm at 10MHz, and settling time is 64ns to 0.01% for a 2V step - all contingent on strict adherence to PCB guidelines including local 0.1µF bypassing at all four supply pins and ground-plane integrity.

Key Specifications

Pinout & Package

OPA628AU is housed in an 8-pin SOIC (SO-8) surface-mount package with exposed pad not present; θ_JA = 100°C/W. Pin functions are validated per official Burr-Brown PDS-1204B datasheet and block diagram.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar low-distortion wideband operational amplifier applications.

Compared with OPA628AU, OPA637BP trades video-grade distortion performance for raw bandwidth, while LMH6629MA sacrifices dual-supply headroom and broadcast validation for lower noise and higher speed - making OPA628AU uniquely balanced for precision video and mixed-signal interface roles.

Availability

OPA628AU is available at Aetrix Electronics and suitable for broadcast infrastructure, medical imaging systems, and precision data acquisition requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for OPA628AU 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

Burr-Brown Corporation, acquired by Texas Instruments in 2000, specialized in high-precision analog ICs for measurement, signal conditioning, and data conversion.

The OPA628AU belongs to Burr-Brown's OPAxx8 ultra-low-distortion op amp family, designed specifically for broadcast video, medical imaging, and high-resolution data converter interfacing where differential gain/phase integrity and wideband SFDR are non-negotiable.

FAQ

What is the maximum capacitive load the OPA628AU can drive without instability?

The OPA628AU remains stable with capacitive loads up to 20pF when properly bypassed. For loads exceeding 20pF - such as flash ADC inputs - a 5Ω to 25Ω series isolation resistor must be placed between the OPA628AU output and the load capacitance to preserve phase margin and prevent peaking or oscillation. This requirement is explicitly validated in the datasheet's "Capacitive Loads" section and confirmed by typical performance curves showing stability boundaries.

Does the OPA628AU require external offset voltage adjustment?

No, the OPA628AU does not require external offset voltage adjustment for most applications. Its input offset voltage is laser-trimmed during wafer fabrication to ≤500µV at 25°C, with drift limited to ±6µV/°C over temperature. The datasheet explicitly states that external nulling is unnecessary in standard configurations and warns that added circuitry may degrade thermal drift performance or introduce noise coupling.

Can the OPA628AU operate from a single supply?

No, the OPA628AU is specified and characterized exclusively for dual-supply operation at ±5VDC (±4.5V to ±6V derated). Its pinout requires four distinct supply connections (+VCC/–VCC for input stage and +VCC/–VCC for output stage), and its common-mode input range is centered at 0V (±2.5V). Single-supply operation is not supported, and attempting it risks violating absolute maximum ratings and invalidating all AC/DC specifications.

What is the purpose of the four separate power supply pins on the OPA628AU?

The four separate supply pins (+VCC/–VCC for input stage; +VCC/–VCC for output stage) physically isolate the input differential pair from the output transistors to eliminate coupling through package parasitics. This architecture maintains >100dB PSRR and CMRR up to 10MHz, prevents output-stage switching noise from modulating input bias currents, and enables the OPA628AU's 0.015% differential gain performance in video applications - a feature not achievable with conventional dual-supply op amps.

Is the OPA628AU pin-compatible with other OPA-series op amps like the OPA627?

No, the OPA628AU is not pin-compatible with the OPA627 or other members of the OPAxx7/xx8 family. It uses an 8-pin SOIC package with a unique pin assignment: pins 1, 2, 5, 7, and 8 are dedicated to supply rails and NC, differing fundamentally from the standard 8-pin DIP/SOIC op amp layout (e.g., OPA627 has power on pins 4 and 8, inputs on 2/3, output on 6). Substitution requires PCB redesign and layout validation per the OPA628AU's specific supply decoupling and grounding rules.