Texas Instruments OPA2228U

Overview

OPA2228U from Texas Instruments is a dual high-precision, low-noise operational amplifier optimized for closed-loop gains ≥5, delivering 33 MHz gain bandwidth, 11 V/µs slew rate, and 3 nV/√Hz input voltage noise. It operates from ±2.5 V to ±18 V supplies and targets professional audio signal chains, precision data acquisition front-ends, and spectral analysis instrumentation where AC fidelity and DC accuracy coexist.

For engineers reviewing the OPA2228U datasheet, OPA2228U pinout, OPA2228U application, or OPA2228U equivalent, key selection criteria include its minimum stable gain of 5 V/V, 138 dB CMRR at DC, 160 dB open-loop gain, ±75 µV max input offset voltage, and SOIC-8 package compatibility with space-constrained analog signal conditioning designs.

Technical Context

The OPA2228U implements a compensated bipolar input stage enabling high-speed operation without external compensation when configured for G ≥ 5. Its architecture suppresses output phase reversal and supports rail-to-rail output swing within ±3.5 V of supply rails under 600 Ω load.

It features matched dual-channel topology with 0.2 µV/V channel separation at DC, enabling accurate differential signal processing in instrumentation amplifiers and active filter banks without crosstalk-induced measurement error.

Key Specifications

Pinout & Package

OPA2228U is housed in an 8-pin SOIC (SO-8) package measuring 4.90 mm × 3.91 mm, optimized for automated PCB assembly and thermal performance (θ_JA = 101.9°C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with OPA2227U and AD8620ARZ, the OPA2228U delivers the highest speed-noise product (33 MHz / 3 nV/√Hz) among dual precision op-amps in SOIC-8, making it optimal for wideband, low-distortion signal chains where gain ≥5 is architecturally feasible.

Availability

OPA2228U is available at Aetrix Electronics and suitable for professional audio equipment, precision data acquisition systems, and spectral analysis instrumentation requiring stable component supply and long-term manufacturability.

Supply support for OPA2228U 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 OPAx22x product line was engineered specifically for mixed-signal applications demanding simultaneous high AC performance and DC precision-targeting audio, instrumentation, and test & measurement markets.

FAQ

What is the minimum closed-loop gain required for stable operation of the OPA2228U?

The OPA2228U 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 will cause oscillation. The OPA2228U datasheet explicitly specifies "Minimum Closed-Loop Gain: 5 V/V" in Section 6.7. For lower-gain applications, the pin-compatible OPA2227U is recommended.

Does the OPA2228U support single-supply operation?

Yes, the OPA2228U supports single-supply operation via asymmetric rails-for example, V+ = +15 V and V– = 0 V (ground), or V+ = +5 V and V– = –2.5 V. Its input common-mode range extends to (V–)+2 V and (V+)-2 V, and output swings to within 3.5 V of either rail under 600 Ω load. Full specifications are guaranteed from ±2.5 V to ±18 V total supply voltage.

How does the OPA2228U's noise performance compare to the OPA2227U?

The OPA2228U and OPA2227U share identical noise specifications: 3 nV/√Hz voltage noise density at 1 kHz and 90 nV_p-p (0.1–10 Hz). Both devices use the same bipolar input stage topology optimized for low 1/f and broadband noise. The primary distinction lies in bandwidth and slew rate-not noise-making them interchangeable in noise-critical applications where gain and stability permit.

Can the OPA2228U drive capacitive loads without instability?

The OPA2228U can drive up to 100 pF directly without external compensation, as verified in Figure 26 and Figure 31 of the SBOS110B datasheet. For loads >100 pF (e.g., coaxial cables, ADC input capacitance), a series isolation resistor (typically 20–100 Ω) placed at the output is required to maintain phase margin. This behavior is consistent across all OPAx228 variants and is not dependent on package type.

Is the OPA2228U pin-compatible with industry-standard op-amps?

Yes, the OPA2228U is a pin-for-pin replacement for the OP-37 and LT1037 in SOIC-8 and PDIP-8 packages, as confirmed in the "OPA228 Replaces OP-37, LT1037, MAX437" feature list. This allows drop-in upgrades with measurable improvements: 33 MHz vs. 63 MHz (OP-37), 11 V/µs vs. 1.7 V/µs (LT1037), and 3 nV/√Hz vs. 3.5 nV/√Hz (OP-37), all while maintaining identical footprint and pin functions.