Texas Instruments OPA228PA

Overview

OPA228PA 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 75 µV maximum input offset voltage across –40°C to +85°C. It operates from ±2.5 V to ±18 V supplies and targets professional audio amplifiers, spectrum analyzers, and precision data acquisition systems.

For engineers reviewing the OPA228PA datasheet, OPA228PA pinout, OPA228PA application, or OPA228PA equivalent, this page provides verified specifications, package-confirmed pin functions, real-world application context, and two validated alternative parts with documented technical and application differences.

Technical Context

The OPA228PA implements a compensated bipolar input stage optimized for stability at closed-loop gains of 5 V/V or higher - not unity-gain stable. Its 33 MHz gain-bandwidth product and 10 V/µs slew rate enable fast settling (1.5 µs to 0.1%) in high-speed precision signal conditioning paths.

It achieves 138 dB common-mode rejection and 160 dB open-loop gain while maintaining 3 nV/√Hz input voltage noise density at 1 kHz and ≤10 nA input bias current - enabling high-resolution measurements in low-level sensor interfaces without compromising bandwidth.

Key Specifications

Pinout & Package

OPA228PA is supplied in an 8-pin PDIP (plastic dual in-line package) with 0.3-inch body width and standard through-hole footprint. Thermal resistance R_θJA = 48.9°C/W enables reliable operation at full rated load without forced airflow.

Key Features

Applications

Equivalent & Alternatives

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

Compared with OPA228U and OPA211AIDR, the OPA228PA uniquely combines accessible offset trim terminals, through-hole thermal robustness, and 33-MHz bandwidth - making it the only option supporting both lab-grade calibration and industrial thermal cycling without layout redesign.

Availability

OPA228PA is available at Aetrix Electronics and suitable for professional audio amplifier design, spectrum analyzer development, and industrial data acquisition systems requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for OPA228PA 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 leadership in precision op amp innovation.

The OPAx228 series was designed specifically for high-fidelity signal chains demanding simultaneous ac bandwidth and dc precision - bridging the gap between legacy OP27-class devices and modern high-speed precision amplifiers.

FAQ

What is the minimum closed-loop gain required for stable operation of the OPA228PA?

The OPA228PA requires a minimum closed-loop gain of 5 V/V for stable operation. It is not unity-gain stable. This is explicitly specified in the Electrical Characteristics table (Section 6.8) and confirmed in the Detailed Description (Section 7.1). Using the OPA228PA at gains below 5 risks oscillation due to insufficient phase margin. For unity-gain applications, the pin-compatible OPA227PA is the recommended alternative.

Does the OPA228PA include offset trim pins, and how are they used?

Yes, the OPA228PA includes two dedicated offset trim pins: Pin 1 (Offset Trim) and Pin 8 (Trim). These connect to the ends of a 10-kΩ potentiometer, with the wiper grounded, allowing manual nulling of input offset voltage to <1 µV in final calibration. This feature is retained from the industry-standard OP27/OP37 architecture and is absent in many newer precision op amps like the OPA211 series.

What is the maximum capacitive load the OPA228PA can drive without instability?

The OPA228PA can drive up to 100 pF capacitive load stably in unity-gain follower configuration, as verified in Figure 6-31 (Small-Signal Overshoot vs Load Capacitance) and confirmed by typical step-response waveforms (Figures 6-32–6-34). For loads exceeding 100 pF, external isolation resistance (e.g., 10–50 Ω in series with the output) is required to maintain phase margin.

Is the OPA228PA pin-compatible with the OP27 or OP37 op amps?

Yes, the OPA228PA is a direct pin-for-pin replacement for the OP27 and OP37 in PDIP-8 packages, as explicitly stated in the device description (Section 3): "The OPAx227 and OPAx228 series operational amplifiers are pin-for-pin replacements for the industry-standard OP27 and OP37 with substantial improvements across the board." Pin functions, spacing, and thermal pad layout match exactly.

What is the operating temperature range specified for the OPA228PA?

The OPA228PA is specified for operation from –40°C to +85°C, as documented in Section 6.3 (Recommended Operating Conditions) and Section 6.8 (Electrical Characteristics). This industrial temperature grade is standard for the 'PA' suffix variant and applies across all electrical parameters unless otherwise noted in individual test conditions.