Texas Instruments OPA228UG4

Overview

OPA228UG4 from Texas Instruments is a high-precision, low-noise dual operational amplifier optimized for closed-loop gains ≥5, delivering 33 MHz unity-gain bandwidth, 10 V/µs slew rate, and 138 dB CMRR in an SOIC-8 package. It serves as a pin-for-pin upgrade to OP37 in professional audio preamplifiers, spectrum analyzer front-ends, and precision data acquisition systems requiring simultaneous AC fidelity and DC accuracy.

For engineers reviewing the OPA228UG4 datasheet, OPA228UG4 pinout, OPA228UG4 application, or OPA228UG4 equivalent, key selection criteria include its minimum stable gain of 5 V/V, input voltage noise of 3 nV/√Hz at 1 kHz, ±2.5 V to ±18 V dual-supply operation, and thermal performance validated across –40°C to +85°C industrial temperature range.

Technical Context

The OPA228UG4 employs a compensated bipolar input stage with internal offset trim capability, enabling stable operation only when configured for closed-loop gains of 5 or higher. Its architecture prioritizes wideband AC performance-evidenced by 33 MHz GBW and 1.5 µs settling time to 0.1%-while maintaining precision DC traits including ≤75 µV max input offset voltage and ≤0.6 µV/°C drift.

Unlike the unity-gain-stable OPA227, the OPA228UG4's compensation network trades stability margin for speed, resulting in higher slew rate (10 V/µs vs. 2.3 V/µs) and lower small-signal overshoot at high capacitive loads when used within its specified gain range.

Key Specifications

Pinout & Package

OPA228UG4 is housed in an 8-pin SOIC (SO-8) package with standard dual-opamp pinout and two unused trim pins. Thermal resistance R_θJA is 110.1°C/W, requiring moderate PCB copper area for continuous 3.8 mA per amplifier operation at full temperature range.

Key Features

Applications

Equivalent & Alternatives

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

Compared with OPA228UG4, OPA227U offers guaranteed unity-gain stability at the cost of bandwidth and slew rate, while AD827ARZ delivers higher speed but sacrifices noise performance and trim flexibility-making OPA228UG4 optimal for balanced AC/DC precision in G ≥ 5 signal chains.

Availability

OPA228UG4 is available at Aetrix Electronics and suitable for professional audio preamplifiers, spectrum analyzer front-ends, and industrial data acquisition systems requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for OPA228UG4 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 heritage in precision op-amp design and manufacturing.

The OPAx22x series was developed to address demanding mixed-signal applications requiring simultaneous high-speed AC response and laboratory-grade DC accuracy-targeting test & measurement, professional audio, and industrial instrumentation markets.

FAQ

What is the minimum closed-loop gain required for stable operation of the OPA228UG4?

The OPA228UG4 requires a minimum closed-loop gain of 5 V/V for stable operation. This is a hard constraint due to its internal compensation; using it at unity gain or G = 2 will cause oscillation or excessive ringing. The OPA228UG4 datasheet explicitly specifies "Minimum closed-loop gain: 5 V/V" under Electrical Characteristics, and Figure 6-23 confirms degraded settling behavior below this threshold. Always verify gain configuration before layout.

Does the OPA228UG4 support single-supply operation?

Yes, the OPA228UG4 supports single-supply operation from 4.5 V to 36 V, as confirmed in Section 6.3 Recommended Operating Conditions. However, its input common-mode range is limited to (V–)+2 V to (V+)-2 V, and output swing does not reach the rails-so proper biasing (e.g., mid-supply reference) is required for true single-supply signal chain use. Dual-supply ±2.5 V to ±18 V remains its most common configuration.

How does the OPA228UG4 compare to the industry-standard OP37?

The OPA228UG4 is a direct pin-for-pin replacement for the OP37, offering substantial improvements: 33 MHz GBW (vs. 63 MHz for OP37-but OPA228UG4 achieves usable bandwidth with lower distortion), 10 V/µs slew rate (vs. 12 V/µs), 3 nV/√Hz input noise (vs. 4.5 nV/√Hz), and 138 dB CMRR (vs. 110 dB). Unlike OP37, OPA228UG4 includes internal offset trim pins and guarantees performance over –40°C to +85°C.

What is the purpose of Pins 1 and 8 on the OPA228UG4?

Pins 1 and 8 on the OPA228UG4 are dedicated offset voltage trim terminals. Connecting a 20-kΩ potentiometer between them allows manual nulling of input offset voltage down to <1 µV-critical for high-accuracy DC-coupled applications like weigh scales or precision current sensing. If trimming is unnecessary, both pins may be left floating without affecting operation, as stated in Table 5-1.

Can the OPA228UG4 drive heavy capacitive loads without instability?

The OPA228UG4 can drive moderate capacitive loads (≤100 pF) stably in G ≥ 5 configurations, as shown in Figure 6-31. For heavier loads (e.g., >500 pF), external isolation resistance (e.g., 50–100 Ω in series with the output) is required to maintain phase margin. Its SOIC-8 package thermal resistance (R_θJA = 110.1°C/W) also limits sustained output current into low-impedance capacitive loads-always verify junction temperature rise using Equation: T_J = T_A + P_DISS × R_θJA.