Texas Instruments OPA338UA

Overview

OPA338UA from Texas Instruments is a single, rail-to-rail output CMOS operational amplifier optimized for non-unity-gain stable operation (G ≥ 5), delivering 12.5MHz gain-bandwidth, 4.6V/µs slew rate, and 120dB open-loop gain at 5V supply. It operates from 2.5V to 5.5V with 525µA quiescent current per amplifier and supports photodiode pre-amplification in battery-powered medical instruments.

For engineers reviewing the OPA338UA datasheet, OPA338UA pinout, OPA338UA application, or OPA338UA equivalent, key selection criteria include minimum stable gain requirement (G ≥ 5), SOT23-5/SO-8 package compatibility, rail-to-rail output swing down to 125mV from rails (RL = 25kΩ), FET-input bias current ≤10pA, and low-noise performance (26nV/√Hz) in precision analog front-ends.

Technical Context

The OPA338UA uses advanced CMOS process technology to achieve high-speed, low-input-bias-current amplification while maintaining rail-to-rail output swing and ground-referenced input common-mode range (−0.2V to V+ − 1.2V). Its internal compensation is optimized for closed-loop gains ≥5, enabling stable 12.5MHz bandwidth without external compensation in G = 5 configurations.

Unlike the unity-gain-stable OPA337 series, the OPA338UA's frequency response exhibits a −20dB/decade roll-off up to ~3MHz (f_C), beyond which phase margin degrades below stability thresholds for gains <5 - requiring explicit compensation (e.g., 68pF capacitor in unity-gain buffer) if used at lower gains.

Key Specifications

Pinout & Package

OPA338UA is available in SOIC-8 (D package), with 8-pin surface-mount configuration and standard industry pinout. Thermal resistance θ_JA = 150°C/W enables reliable operation at full rated temperature range (−40°C to +85°C).

Key Features

Applications

Equivalent & Alternatives

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

Compared with OPA337UA and OPA340UA, the OPA338UA provides higher bandwidth and slew rate specifically for gain ≥5 configurations, making it optimal for high-fidelity signal conditioning where speed outweighs unity-gain flexibility or ultra-low bias requirements.

Availability

OPA338UA is available at Aetrix Electronics and suitable for battery-powered instruments, photodiode pre-amplifiers, and medical instrumentation requiring stable component supply across industrial temperature ranges (−40°C to +85°C).

Supply support for OPA338UA 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 over 90 years of innovation in precision amplifiers and signal chain solutions.

The OPA338UA belongs to TI's MicroAmplifier™ series, designed for space-constrained, low-power, high-accuracy applications including portable medical devices, test equipment, and sensor interfaces where rail-to-rail output and FET-input performance are critical.

FAQ

What is the minimum stable gain for OPA338UA?

The OPA338UA is internally compensated for minimum closed-loop gain of 5 (G ≥ 5). Using it at lower gains without external compensation risks instability and peaking in frequency response. For unity-gain applications, a 68pF capacitor network (as shown in TI SBOS077B Figure 3) is required to ensure stability while retaining its 4.6V/µs slew rate advantage over the OPA337UA.

Does OPA338UA support true single-supply operation with input referenced to ground?

Yes. The OPA338UA features an input common-mode voltage range extending from (V−) − 0.2V to (V+) − 1.2V, allowing direct connection of the non-inverting input to ground in single-supply configurations. This eliminates the need for input biasing networks in sensor interfaces like photodiode transimpedance amplifiers, simplifying PCB layout and reducing component count.

What is the maximum capacitive load OPA338UA can drive without compensation?

The OPA338UA can reliably drive up to 100pF capacitive loads in G = 5 configurations without external compensation, as verified by small-signal step response testing in the SBOS077B datasheet. Driving larger loads (e.g., >200pF) or using lower gains requires isolation resistors or feedback network adjustments to maintain phase margin above 45°.

How does OPA338UA's noise performance compare to OPA337UA?

The OPA338UA has identical input voltage noise density (26nV/√Hz at 1kHz) and input current noise (0.6fA/√Hz) as the OPA337UA, confirming shared CMOS process and input stage design. However, its higher 12.5MHz bandwidth increases integrated noise in wideband applications - designers should use band-limiting filters when noise-critical gain stages exceed 100kHz.

Is OPA338UA pin-compatible with other SOIC-8 op-amps like LM358 or TL072?

No. The OPA338UA uses a non-standard SOIC-8 pinout with pins 1 (−In), 2 (+In), 3 (Out), 4 (V−), 5/6/8 (NC), and 7 (V+), differing from industry-standard dual op-amps. Substituting into existing LM358 or TL072 layouts would require PCB redesign due to NC pin placement and missing dual-amplifier functionality - only single-channel replacements with matching pin functions are viable.