Texas Instruments OPA228U/2K5

Overview

OPA228U/2K5 from Texas Instruments is a dual-channel, high-precision, low-noise operational amplifier optimized for closed-loop gains ≥5, delivering 33 MHz unity-gain bandwidth, 10 V/µs slew rate, and 3 nV/√Hz input voltage noise. It operates from ±2.5 V to ±18 V supplies and is used in professional audio amplifiers, spectrum analyzers, and precision data acquisition systems where wide dynamic range and fast settling are critical.

For engineers reviewing the OPA228U/2K5 datasheet, OPA228U/2K5 pinout, OPA228U/2K5 application, or OPA228U/2K5 equivalent, key selection criteria include minimum closed-loop gain requirement (≥5), thermal performance in SOIC-8 (R_θJA = 101.9 °C/W), CMRR of 138 dB, and compatibility with ±15 V industrial signal conditioning rails.

Technical Context

The OPA228U/2K5 implements a compensated bipolar input stage optimized for stability at G ≥ 5, with internal compensation enabling 33 MHz bandwidth without external components. Its architecture delivers simultaneous high dc precision (75 µV max offset, 0.6 µV/°C max drift) and ac performance (1.5 µs settling to 0.1% at G = 1).

Unlike the unity-gain-stable OPA227, the OPA228U/2K5 trades gain flexibility for speed: it requires ≥5× closed-loop gain for stable operation, achieves 11 V/µs typical slew rate, and maintains 138 dB CMRR up to 1 kHz-critical for rejecting power supply ripple in high-resolution sensor front-ends.

Key Specifications

Pinout & Package

OPA228U/2K5 is supplied in an 8-pin SOIC (SO-8) package with standard dual-opamp pinout and no internal connection on pin 5. Thermal resistance is R_θJA = 101.9 °C/W, requiring moderate PCB copper area for continuous 3.8 mA per channel operation at 85°C ambient.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-speed precision op-amp applications.

Compared with OPA228U/2K5, OPA2228U/2K5 is its exact TI-qualified replacement with identical performance, while AD827ARZ offers lower cost but sacrifices 30% bandwidth, 33% noise performance, and dc precision-making it unsuitable for high-resolution measurement systems.

Availability

OPA228U/2K5 is available at Aetrix Electronics and suitable for professional audio amplifier design, spectrum analyzer front-ends, and precision data acquisition systems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for OPA228U/2K5 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 broad industrial, automotive, and communications product portfolios.

The OPA228U/2K5 belongs to TI's OPAx228 precision op-amp family, engineered for applications demanding simultaneous high-speed ac response and sub-100-µV dc accuracy-particularly in test equipment, audio infrastructure, and sensor signal chains.

FAQ

What is the minimum closed-loop gain required for stable operation of the OPA228U/2K5?

The OPA228U/2K5 requires a minimum closed-loop gain of 5 V/V for stable operation. This is a hard architectural constraint due to internal compensation; using it at unity gain or G = 2 risks oscillation and degraded phase margin. The OPA228U/2K5 datasheet explicitly specifies "Minimum closed-loop gain: 5 V/V" in Section 6.8, and Figure 6-23 confirms instability below this threshold via increased settling time and overshoot.

Does the OPA228U/2K5 support single-supply operation?

Yes, the OPA228U/2K5 supports single-supply operation from 4.5 V to 36 V (Section 6.3). When operated from +5 V to +36 V with ground as V−, its input common-mode range extends from (V−) + 2 V to (V+) − 2 V, and output swings to within 2 V of each rail under light load. For true rail-to-rail input/output, an external level-shifting network is required.

What is the thermal resistance (R_θJA) of the OPA228U/2K5 in its SOIC-8 package?

The OPA228U/2K5 in SOIC-8 (U-grade) has a junction-to-ambient thermal resistance (R_θJA) of 101.9 °C/W, as specified in Table 6.5 of the SBOS110C datasheet. This value assumes standard JEDEC 2S2P board layout; adding 1-in² copper pour beneath the package reduces R_θJA by ~15 °C/W in typical layouts.

How does the OPA228U/2K5 differ from the OPA227U/2K5 in terms of bandwidth and stability?

The OPA228U/2K5 provides 33 MHz bandwidth and 10 V/µs slew rate but requires ≥5× closed-loop gain for stability, whereas the OPA227U/2K5 offers 8 MHz bandwidth and 2.3 V/µs slew rate with unity-gain stability. Both share identical offset (±75 µV), noise (3 nV/√Hz), and CMRR (138 dB) specs-but their compensation schemes are mutually exclusive and not interchangeable without circuit redesign.

Is the OPA228U/2K5 pin-compatible with industry-standard op-amps like the OP27 or OP37?

No, the OPA228U/2K5 is not pin-compatible with OP27 or OP37. While the OPAx227/228 series are described as "pin-for-pin replacements" for OP27/OP37 in the datasheet introduction, that statement applies only to the single-channel OPA227 and OPA228 variants (8-pin DIP/SOIC), not the dual-channel OPA2227/OPA2228. The OPA228U/2K5 is a dual op-amp with different pinout (e.g., pin 5 = +In B, not offset trim) and cannot substitute for OP27/OP37 without PCB revision.