Texas Instruments OPA228UA/2K5

Overview

OPA228UA/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 75 µV maximum input offset voltage. It operates from ±2.5 V to ±18 V supplies and serves in professional audio amplifiers, spectrum analyzers, and precision data acquisition systems where wide bandwidth and low distortion are critical.

For engineers reviewing the OPA228UA/2K5 datasheet, OPA228UA/2K5 pinout, OPA228UA/2K5 application, or OPA228UA/2K5 equivalent, key selection factors include its minimum stable gain of 5 V/V, 138 dB CMRR, 160 dB open-loop gain, 3 nV/√Hz input voltage noise at 1 kHz, and SOIC-8 package compatibility with industry-standard OP37 footprints.

Technical Context

The OPA228UA/2K5 implements a compensated bipolar input stage optimized for high-speed, high-precision closed-loop operation - not unity-gain stability - requiring ≥5 V/V gain for stable performance. Its architecture delivers 33 MHz bandwidth and 10 V/µs slew rate while maintaining 138 dB common-mode rejection and 160 dB open-loop DC gain across –40°C to +85°C.

Unlike the OPA227 series, the OPA228 family uses internal compensation tailored for higher closed-loop gain configurations, resulting in faster settling (1.5 µs to 0.1%) and lower THD+N (0.00005% at 1 kHz), making it suitable for AC-coupled signal chains demanding both dynamic fidelity and DC accuracy.

Key Specifications

Pinout & Package

OPA228UA/2K5 is housed in an 8-pin SOIC (SO-8) package with standard dual-op-amp pinout and no internal connection on Pin 5. Thermal resistance R_θJA is 101.9°C/W (SOIC), supporting continuous operation at ≤+85°C ambient with moderate power dissipation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with OPA227UA/2K5 and AD8620ARZ, the OPA228UA/2K5 uniquely balances 33 MHz bandwidth, 10 V/µs slew rate, and 3 nV/√Hz noise - making it the only option among the three capable of driving 10-V, 5-MHz signals with <0.1% settling error and <–120 dB THD+N.

Availability

OPA228UA/2K5 is available at Aetrix Electronics and suitable for professional audio equipment, spectrum analyzer signal chains, and industrial data acquisition systems requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for OPA228UA/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 decades of expertise in precision op-amp design and manufacturing.

The OPAx228 product line was engineered specifically for high-fidelity, wide-bandwidth analog signal conditioning in test & measurement, professional audio, and precision instrumentation - emphasizing speed, noise, and DC accuracy in a single platform.

FAQ

Is OPA228UA/2K5 unity-gain stable?

No, OPA228UA/2K5 is not unity-gain stable. It is internally compensated for minimum closed-loop gain of 5 V/V. Attempting G = 1 operation risks oscillation. For unity-gain applications, use OPA227UA/2K5 instead - which shares the same SOIC-8 package and pinout but guarantees stability at G ≥ 1.

What is the maximum capacitive load OPA228UA/2K5 can drive without instability?

OPA228UA/2K5 can safely drive ≤100 pF capacitive loads in G ≥ 5 configurations with proper PCB layout and local 0.1-µF supply decoupling. Driving >150 pF requires isolation resistor (e.g., 10–50 Ω) between output and load, as shown in TI's OPA228 application note SBAA343.

Does OPA228UA/2K5 support single-supply operation?

Yes, OPA228UA/2K5 supports single-supply operation from 4.5 V to 36 V (e.g., +5 V or +12 V with ground as V−). Input common-mode range extends to (V−) + 2 V, and output swings to (V−) + 2 V and (V+) − 2 V, enabling rail-to-rail input/output compatibility in properly biased circuits.

How does OPA228UA/2K5 compare to OP37 in pin compatibility and performance?

OPA228UA/2K5 is a direct pin-for-pin replacement for OP37 in SOIC-8 (U) and PDIP-8 (P) packages. It improves upon OP37 with 33 MHz vs 63 MHz GBW (note: OP37 is 63 MHz, but OPA228 offers superior noise: 3 nV/√Hz vs OP37's 3.5 nV/√Hz), 10 V/µs vs 12 V/µs slew rate, and 138 dB CMRR vs 110 dB - while maintaining identical pin functions and footprint.

What thermal derating applies to OPA228UA/2K5 in SOIC-8 at +70°C ambient?

With R_θJA = 101.9°C/W and max T_J = 150°C, OPA228UA/2K5 dissipating 150 mW (3.8 mA × ±15 V) reaches junction temperature = 70°C + (150 mW × 101.9°C/W) = 85.3°C - within safe margin. At +70°C ambient, full rated performance is maintained up to 225 mW total package dissipation.