Texas Instruments OPA2686U

Overview

OPA2686U from Texas Instruments (formerly Burr-Brown) is a dual, wideband, low-noise voltage-feedback operational amplifier optimized for high-speed differential signal conditioning. It delivers 1.4 nV/√Hz input voltage noise, 1.6 GHz gain bandwidth product, and 250 MHz closed-loop bandwidth at G = +10, enabling precision xDSL receiver amplification, ultrasound preamplification, and matched I/Q channel amplification in RF front-ends.

For engineers reviewing the OPA2686U datasheet, OPA2686U pinout, OPA2686U application, or OPA2686U equivalent, this page provides verified technical context, exact SO-8 pin mapping, real-world transimpedance and ADC driver use cases, and two validated alternative op amps with documented performance trade-offs.

Technical Context

The OPA2686U implements a decompensated voltage-feedback architecture requiring minimum stable gain of +7 V/V, with guaranteed flatness at +10 V/V. Its dual-channel design ensures ≤0.02% differential gain and ≤0.02° differential phase error under NTSC conditions, supporting professional video and high-fidelity analog front-ends.

Each channel operates at ±5 V supply with 12 mA quiescent current, delivering 600 V/µs slew rate and –90 dBc 2nd-harmonic distortion at 5 MHz (RL = 500 Ω). Channel-to-channel crosstalk is –70 dBc at 5 MHz, confirming tight matching for differential ADC driving and I/Q signal paths.

Key Specifications

Pinout & Package

OPA2686U is housed in an SO-8 surface-mount package (θ_JA = 125°C/W), rated for –40°C to +85°C operation. Pin numbering follows standard SO-8 top-view convention with exposed pad not electrically connected.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual wideband op amp applications.

Compared with LMH6629MA/NOPB and ADA4898-2ARZ, the OPA2686U uniquely balances 1.4 nV/√Hz noise, 600 V/µs slew, and 1.6 GHz GBP in a thermally efficient SO-8 package-making it irreplaceable for VDSL receiver front-ends and high-SFDR ADC drivers demanding simultaneous speed, linearity, and noise performance.

Availability

OPA2686U is available at Aetrix Electronics and suitable for VDSL receiver modules, ultrasound imaging front-ends, professional audio transimpedance circuits, and high-speed data acquisition systems requiring stable component supply across extended temperature ranges.

Supply support for OPA2686U 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 acquired Burr-Brown in 2000 and maintains full legacy support for high-performance analog products including the OPA family. TI is a global leader in precision amplifiers, data converters, and power management ICs.

The OPA2686U belongs to TI's high-speed, low-noise operational amplifier product line, designed specifically for broadband communications, medical imaging, and test equipment requiring exceptional dynamic range and channel matching.

FAQ

What is the minimum stable gain for OPA2686U, and why does it matter?

The OPA2686U requires a minimum stable gain of +7 V/V due to its decompensated voltage-feedback architecture. Operating below this gain risks peaking or oscillation in closed-loop configurations. This constraint directly impacts transimpedance amplifier design-where feedback resistor selection must ensure noise gain ≥7. For example, in a single-stage photodiode amplifier with 10 kΩ RF, the effective noise gain exceeds +7 only if input capacitance remains below ~15 pF. The OPA2686U datasheet provides external compensation techniques (e.g., Figure 5) to safely operate at lower signal gains while preserving slew rate and distortion performance.

Can OPA2686U drive a 50 Ω load directly, and what are the implications?

Yes, the OPA2686U can drive a 50 Ω load directly, but with reduced output swing and increased power dissipation. At ±5 V supplies, its guaranteed output voltage swing into 100 Ω is ±3.3 V, implying ~±2.8 V into 50 Ω based on internal output impedance (~0.008 Ω) and thermal limits. Driving 50 Ω continuously draws ~112 mA per channel (2 × 2.8 V / 50 Ω), exceeding the 80 mA sourcing/sinking specification and risking thermal shutdown. For sustained 50 Ω operation, use series termination (e.g., 45 Ω in series with 50 Ω load) or buffer stages. The OPA2686U is optimized for 100–500 Ω loads in high-fidelity applications like ADC drivers and VDSL receivers.

How does OPA2686U achieve matched channel performance for I/Q applications?

The OPA2686U achieves matched channel performance through monolithic dual-die integration with laser-trimmed resistor networks and symmetrical layout. Measured parameters include ≤0.02% differential gain error and ≤0.02° differential phase error at NTSC frequencies, confirming <0.01% amplitude/phase mismatch between channels. This matching is process-controlled-not post-package trimmed-and holds across –40°C to +85°C. In practice, this allows direct use in quadrature demodulators without external calibration, reducing BOM count and PCB area versus discrete single-channel solutions. The –70 dBc channel-to-channel crosstalk at 5 MHz further ensures isolation during simultaneous high-frequency signal processing.

What decoupling is required for OPA2686U to maintain 250 MHz bandwidth?

To maintain 250 MHz closed-loop bandwidth and prevent supply-induced oscillation, the OPA2686U requires localized, multi-value decoupling: a 0.1 µF X7R ceramic capacitor placed ≤2 mm from each supply pin (V+ and V−), plus a 6.8 µF tantalum or polymer capacitor within 10 mm. The 0.1 µF cap handles high-frequency transients (>10 MHz), while the bulk capacitor stabilizes mid-band supply impedance. PCB layout must use solid ground planes, avoid vias in supply traces, and route decoupling caps directly to supply pins with short, wide traces. Failure to meet these requirements causes gain peaking above 100 MHz and degraded harmonic distortion-verified in TI's SBOS064 characterization (Figure 1).

Is OPA2686U suitable for single-supply operation?

No, the OPA2686U is not characterized or specified for true single-supply operation. Its input common-mode range is ±3.2 V (min) at ±5 V supplies, and output swing is asymmetric below ground-requiring dual ±5 V rails for full dynamic range. While it may function with a split-rail derived from a single supply (e.g., using a charge pump or rail splitter), TI does not guarantee performance outside the –40°C to +85°C range or ±5 V nominal supply. For single-supply applications, TI recommends alternatives like the OPA2837 (rail-to-rail I/O, 1.5 GHz GBP) or THS4561 (fully differential amplifier with integrated common-mode control). The OPA2686U's design assumes symmetric bipolar supplies for optimal distortion and bandwidth.