AD8641ARZ

Overview

The AD8641ARZ is a single-channel, low power, precision JFET input operational amplifier manufactured by Analog Devices Inc. It features rail-to-rail output capability and operates within an extended industrial temperature range of −40°C to +125°C. The device supports single-supply voltages from 5 V to 26 V or dual supplies from ±2.5 V to ±13 V. Key electrical specifications include a maximum supply current of 250 µA, a maximum input bias current of 1 pA, and a maximum offset voltage of 750 µV. It offers a gain bandwidth product of 3 MHz, a slew rate of 2 V/µs at 5 V, and unity-gain stability without phase reversal.

Feature Summary

• Features extremely low input bias current suitable for high-impedance signal sources
• Provides rail-to-rail output swing in single-supply systems
• Maintains stability with capacitive loads exceeding 500 pF
• Operates as a unity-gain stable amplifier without phase reversal

Applications

• Photodiode amplifiers
• Precision current sensing
• Line- or battery-powered instruments
• Medical instrumentation
• Portable audio equipment

Procurement Notes

Verify the package type matches the required PCB footprint, specifically the 8-Lead Standard Small Outline Package (R-8). Confirm RoHS compliance status indicated by the 'Z' suffix. Ensure the operating environment falls within the specified -40°C to +125°C temperature range. Check datasheet revisions for any updates to absolute maximum ratings or thermal resistance values before finalizing design integration.

Selection Notes

Select this component when low quiescent current and high DC precision are required simultaneously. The JFET input stage minimizes loading on high-impedance sensors compared to CMOS alternatives. Consider the rail-to-rail output if maximizing dynamic range in single-supply applications is critical. Evaluate the 3 MHz bandwidth against system speed requirements to ensure adequate settling time for precision filtering tasks.

Part Context

This part belongs to the AD864x family of low power precision amplifiers, which includes dual (AD8642) and quad (AD8643) channel variants. All members share similar electrical characteristics but differ in channel count and available package options. The AD8641ARZ specifically denotes the single-channel version housed in an 8-lead SOIC package, designed for space-constrained designs requiring minimal heat dissipation.

Replacement Considerations

Direct pin-compatible substitutes within the same family include the AD8642ARZ (dual channel) and AD8643ARZ (quad channel), provided additional channels are acceptable. Verify that replacement parts maintain the same R-8 package dimensions and lead spacing to ensure mechanical compatibility without board redesign.

FAQ

Does the AD8641ARZ support input signals near the negative supply rail?

Yes, the input voltage range extends to the negative supply rail (VEE), allowing operation down to 0 V in single-supply configurations.

What is the maximum capacitive load the output can drive stably?

The outputs remain stable with capacitive loads of more than 500 pF.

Is the AD8641ARZ unity-gain stable?

Yes, the device is unity-gain stable and does not exhibit phase reversal when the input common-mode voltage approaches the negative rail.