Texas Instruments OPA637AU/2K5

Overview

OPA637AU/2K5 from Texas Instruments is a precision JFET-input operational amplifier optimized for high-speed, low-noise signal conditioning in gain ≥ 5 configurations. It delivers 4.5 nV/√Hz input voltage noise at 10 kHz, 450 ns settling time to 0.01%, and ±500 µV max input offset voltage over –40°C to +125°C. It operates from ±4.5 V to ±18 V supplies and serves as a DAC output amplifier or high-impedance sensor interface in test equipment.

For engineers reviewing the OPA637AU/2K5 datasheet, OPA637AU/2K5 pinout, OPA637AU/2K5 application, or OPA637AU/2K5 equivalent, key selection criteria include its minimum stable gain of 5, SOIC-8 package compatibility, 80 MHz gain-bandwidth product at G = 10, and thermal performance (R_θJA = 107.9 °C/W) in industrial environments.

Technical Context

The OPA637AU/2K5 uses dielectrically isolated complementary NPN/PNP process technology with laser-trimmed input circuitry to achieve precision FET performance-low input bias current (±10 pA max), low drift (±2.5 µV/°C max), and high open-loop gain (106 dB min). Its cascode input stage maintains low IB across wide common-mode range (±11.5 V).

Unlike the unity-gain-stable OPA627, the OPA637AU/2K5 is internally compensated for noise gain ≥ 5, enabling higher bandwidth (80 MHz GBW) and slew rate (135 V/µs at G = –4) without external compensation. Stability is verified per Figure 6-2 in SBOS165C for noninverting G ≥ 5 or inverting G ≥ 4 configurations.

Key Specifications

Pinout & Package

OPA637AU/2K5 is packaged in an 8-pin SOIC (D package) with exposed pad not connected internally. All pins are electrically defined per TI SBOS165C Rev C: Pins 1, 5, and 8 are no-connect (NC); Pin 2 is inverting input (–IN); Pin 3 is noninverting input (+IN); Pin 4 is negative supply (V–); Pin 6 is output (OUT); Pin 7 is positive supply (V+).

Key Features

Applications

Equivalent & Alternatives

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

Compared with OPA627AU/2K5, the OPA637AU/2K5 trades unity-gain stability for 78% higher bandwidth and 18% faster settling in gain ≥ 5 circuits; versus ADA4898-1ARMZ, it provides 1000× lower input bias current at the cost of 3.5× higher voltage noise - making it optimal for high-Z, medium-bandwidth precision systems.

Availability

OPA637AU/2K5 is available at Aetrix Electronics and suitable for precision instrumentation, fast data acquisition, and DAC output amplification requiring stable component supply across industrial temperature ranges and long production lifecycles.

Supply support for OPA637AU/2K5 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 delivering analog and embedded processing solutions with emphasis on reliability, precision, and signal-chain integration.

The OPA637AU/2K5 belongs to TI's OPA6x7 precision JFET op amp family, engineered for applications demanding both high speed and ultra-low input bias current - especially in sensor interfaces, metrology, and high-resolution data conversion systems.

FAQ

What is the minimum stable closed-loop gain for OPA637AU/2K5?

The OPA637AU/2K5 is internally compensated for noise gain ≥ 5. This means it remains stable in noninverting configurations with gain ≥ 5 or inverting configurations with gain magnitude ≥ 4. Using it at lower noise gains - such as unity-gain buffers or integrators - risks oscillation and is not recommended. Always verify stability with phase margin simulation when adding capacitive loads or complex feedback networks.

Does OPA637AU/2K5 support single-supply operation?

Yes, OPA637AU/2K5 supports single-supply operation with total supply voltage ranging from 9 V to 36 V (e.g., +36 V and GND). However, its input common-mode range extends only to within 0.5 V of the rails, and output swing is typically ±11.5 V into 1 kΩ - so for true rail-to-rail performance, a dual-supply configuration (e.g., ±15 V) is preferred. Input bias current and offset specifications are guaranteed only over the specified dual-supply operating conditions.

How does OPA637AU/2K5 compare to OPA627AU/2K5 in terms of noise performance?

Both OPA637AU/2K5 and OPA627AU/2K5 share identical broadband voltage noise density: 4.5 nV/√Hz at 10 kHz and 0.34 µV_PP (0.1–10 Hz). Their input current noise is also matched at 2.5 fA/√Hz (100 Hz). The key distinction lies in bandwidth - OPA637AU/2K5 achieves this noise floor at 80 MHz GBW and 135 V/µs slew rate in G ≥ 5, whereas OPA627AU/2K5 delivers it at 45 MHz GBW and 150 V/µs in unity gain. So noise is equal; speed vs. stability is the trade-off.

Can OPA637AU/2K5 drive capacitive loads?

OPA637AU/2K5 can drive ≤30 pF capacitive loads directly without instability. For larger loads (e.g., ADC inputs, cables), external isolation resistance (≥100 Ω) or feedback capacitor compensation (per Figure 6-2 in SBOS165C) is required. Uncompensated capacitive loading degrades phase margin and may cause ringing or oscillation - especially critical in high-gain, high-frequency applications like active filters or photodiode transimpedance stages.

Is the SOIC-8 package of OPA637AU/2K5 RoHS compliant and lead-free?

Yes, the OPA637AU/2K5 in SOIC-8 (D package) is RoHS compliant and lead-free per TI's packaging standards. The device carries the "AU" grade suffix, indicating industrial temperature range (–40°C to +125°C) and green (halogen-free) molding compound. Full compliance documentation, including material declarations and Pb-free conversion reports, is available in TI's official product folder and PCN archives.