Texas Instruments OPA228P

Overview

OPA228P from Texas Instruments is a single-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 3 nV/√Hz input voltage noise. It operates from ±2.5 V to ±18 V supplies and achieves 138 dB CMRR and 160 dB open-loop gain - ideal for spectrum analyzer front-end amplification and professional audio signal conditioning.

For engineers reviewing the OPA228P datasheet, OPA228P pinout, OPA228P application, or OPA228P equivalent, this page provides verified specifications, DIP-8 package layout, real-world use cases in precision AC/DC instrumentation and data acquisition, and two confirmed alternative op-amps with documented functional trade-offs.

Technical Context

The OPA228P uses a compensated bipolar input stage enabling stable operation at minimum closed-loop gain of 5 V/V, unlike unity-gain-stable OPA227 variants. Its 33 MHz gain-bandwidth product and 10 V/µs slew rate support fast settling (1.5 µs to 0.1%) in high-fidelity analog signal chains requiring wide dynamic range and low distortion.

It features laser-trimmed input offset voltage (±75 µV max), ultra-low 1/f noise corner (<10 Hz), and robust ESD protection (1000 V HBM, 250 V CDM). Thermal resistance is 48.9°C/W (R_θJA) in PDIP-8, supporting reliable operation from –40°C to +85°C ambient.

Key Specifications

Pinout & Package

OPA228P is housed in an 8-pin plastic dual in-line package (PDIP-8), through-hole mountable with 0.3-inch body width and standard 0.1-inch pin pitch. Thermal resistance R_θJA = 48.9°C/W enables >300 mW dissipation at +85°C ambient.

Key Features

Applications

Equivalent & Alternatives

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

Compared with OPA228P, OPA227P trades bandwidth for unconditional stability at low gains, while AD827JN offers higher raw speed at the cost of power efficiency and integrated trim capability - making OPA228P the optimal balance for G ≥ 5 precision AC/DC signal chains.

Availability

OPA228P is available at Aetrix Electronics and suitable for spectrum analyzer development, professional audio equipment manufacturing, and industrial AC-DC power monitoring systems requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for OPA228P 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 OPAx228 series was developed specifically for high-fidelity instrumentation and professional audio applications demanding simultaneous low noise, high speed, and dc precision - distinguishing it from general-purpose or rail-to-rail op-amps.

FAQ

What is the minimum closed-loop gain required for stable operation of the OPA228P?

The OPA228P requires a minimum closed-loop gain of 5 V/V for stable operation. Unlike the OPA227P, it is not unity-gain stable. Attempting G = 1 will cause peaking or oscillation due to its internal compensation optimized for higher gains. Always verify phase margin in simulation when using OPA228P in gain-of-5 or higher configurations.

Does the OPA228P include offset voltage trim pins, and how are they used?

Yes, the OPA228P includes dedicated offset trim pins (Pin 1 and Pin 8) for manual nulling of input offset voltage. A 10-kΩ potentiometer is connected between these pins with its wiper tied to V– (Pin 4); adjusting the potentiometer minimizes output offset. This feature is absent in many competing op-amps and enables <10 µV system-level offset in calibrated instruments.

Can the OPA228P operate from a single 5-V supply?

No - the OPA228P is specified for dual-supply operation from ±2.5 V to ±18 V (i.e., total supply range 5 V to 36 V). While it can technically bias with asymmetric rails (e.g., +5 V and ground), its input common-mode range is limited to (V–) + 2 V to (V+) – 2 V, and output swing does not reach rails. For true single-supply 5-V designs, consider TI's OPA350 or similar rail-to-rail devices instead of OPA228P.

How does the OPA228P compare to the industry-standard OP27 in terms of noise and speed?

The OPA228P improves upon the OP27 with 3 nV/√Hz input voltage noise (vs. OP27's 3.5 nV/√Hz) and 33 MHz bandwidth (vs. OP27's 8 MHz), while retaining pin compatibility in PDIP-8 and SO-8 packages. It also offers superior CMRR (138 dB vs. 126 dB) and lower input bias current (10 nA max vs. 80 nA), making OPA228P a direct upgrade path where higher speed and lower noise are critical.

Is the OPA228P suitable for driving capacitive loads, and what is its maximum recommended value?

The OPA228P can drive moderate capacitive loads but is not optimized for heavy C_L. Typical overshoot exceeds 20% above 100 pF at G = –1 (per Figure 6-31), and stability degrades rapidly beyond that. For loads >100 pF, external isolation (e.g., series resistor + feedback capacitor) or a dedicated buffer is recommended. The OPA228P datasheet does not specify a guaranteed stable C_L limit, so derating to ≤50 pF is advised for production designs.