Texas Instruments OPA2681N

Overview

OPA2681N from Texas Instruments is a dual wideband current-feedback operational amplifier with disable control, designed for high-speed single-supply operation. It delivers 225MHz bandwidth at G = +2, 2100V/µs slew rate, and ±4.0V output swing on ±5V supplies - or 1V–4V swing on +5V - enabling RGB line driving and differential ADC input buffering in portable instrumentation and broadband video systems.

For engineers reviewing the OPA2681N datasheet, OPA2681N pinout, OPA2681N application, or OPA2681N equivalent, key selection criteria include its 6mA/ch quiescent current, 25ns enable/100ns disable timing, SO-14 package with dedicated DIS pins per channel, and guaranteed 150mA output drive into 100Ω loads across –40°C to +85°C.

Technical Context

The OPA2681N employs a current-feedback architecture where bandwidth remains stable across gain settings (225MHz at G = +2, 280MHz at G = +1), unlike voltage-feedback amplifiers. Its transimpedance gain (Z_OL) is specified at ≥56kΩ, supporting fast settling (12ns to 0.02%) and low distortion (–79dBc 2nd harmonic @ 5MHz).

It features a proprietary output stage minimizing crossover distortion and voltage headroom - enabling >100mA sourcing/sinking while swinging within 1V of either rail on +5V supply. The disable function (SO-14 only) forces output to high-Z and reduces supply current to <640µA per channel with 25ns/100ns enable/disable transitions.

Key Specifications

Pinout & Package

OPA2681N is housed in a 14-pin SOIC (SO-14) surface-mount package (Package Drawing 235), with thermal resistance θ_JA = 100°C/W. Pin 1 is marked by a beveled corner or dot; pin numbering follows standard SO-14 convention.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar current-feedback op amp applications.

Compared with OPA2680 and OPA2682, the OPA2681N uniquely combines programmable gain, per-channel disable, and highest bandwidth (225MHz) in a dual current-feedback topology - making it optimal for dynamic, multi-channel, power-aware high-speed analog systems.

Availability

OPA2681N is available at Aetrix Electronics and suitable for RGB line driving, differential ADC interfacing, and video multiplexing requiring stable component supply across industrial temperature ranges and long production lifecycles.

Supply support for OPA2681N 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 op amps and precision signal chain solutions.

The OPA2681N belongs to TI's OPA26xx current-feedback op amp family, engineered specifically for broadband video, communications, and instrumentation applications demanding wide bandwidth, low power, and robust single-supply operation.

FAQ

What supply voltages does the OPA2681N support?

The OPA2681N operates from ±5V dual supplies or a single +5V supply. Its absolute maximum rating is ±6.5V, and it functions reliably up to +12V single supply. On +5V, it delivers 1V–4V output swing with >150MHz bandwidth - confirmed in Figure 2 test conditions (RF = 499Ω, RL = 100Ω to 2.5V). The OPA2681N maintains specified performance across –40°C to +85°C.

Does the OPA2681N have a disable function on both channels?

Yes - the OPA2681N (SO-14 package) includes two independent disable pins: Pin 3 (DIS A) and Pin 5 (DIS B). Each controls one amplifier channel. Pulling either pin low disables its respective output (high-Z state) and reduces that channel's supply current to <640µA. Pins left open or held high maintain normal operation. This per-channel control is essential for video multiplexing and power-gated instrumentation.

What is the minimum load impedance the OPA2681N can drive while maintaining specifications?

The OPA2681N is characterized into 100Ω loads (±5V) and 100Ω-to-2.5V (single +5V), with guaranteed ±150mA output current. While it can drive lower impedances (e.g., 50Ω or 25Ω), output swing and distortion degrade - see "OUTPUT VOLTAGE AND CURRENT LIMITATIONS" curve (Page 8). For 75Ω video applications, external series termination (e.g., 82.5Ω) is recommended to maintain 75Ω cable match and minimize reflections without exceeding safe operating area.

How does the OPA2681N compare to the OPA2680 in terms of bandwidth versus gain?

Unlike the voltage-feedback OPA2680, the OPA2681N's current-feedback architecture yields nearly constant bandwidth across gains: 280MHz at G = +1, 225MHz at G = +2, and 185MHz at G = +5. The OPA2680's bandwidth falls sharply with gain (e.g., ~180MHz at G = +2, <100MHz at G = +5). This makes the OPA2681N preferable for variable-gain or wideband fixed-gain systems where consistent frequency response is critical.

Is the OPA2681N pin-compatible with other devices in the OPA26xx family?

No - the OPA2681N (SO-14) is not pin-compatible with the OPA2680 (SO-8) or OPA2682 (SO-8). Its SO-14 layout accommodates dedicated DIS pins (3 & 5) and NC pads absent in 8-pin variants. However, functional equivalents exist: OPA2680 offers superior DC specs; OPA2682 provides fixed +2 gain in smaller footprint. Migration requires PCB redesign due to differing pin count, placement, and disable functionality.