AD8639WARZ

Overview

The AD8639WARZ is a dual-channel, auto-zero operational amplifier manufactured by Analog Devices Inc. It features rail-to-rail output swing and operates on single supplies from 5 V to 16 V or dual supplies from ±2.5 V to ±8 V. Key electrical specifications include a maximum offset voltage of 9 μV, an input bias current of 40 pA (max), and a supply current of 1.3 mA per amplifier. The device offers a gain bandwidth product of 1.5 MHz, a slew rate of 2 V/μs, and high common-mode rejection ratio (CMRR) of 133 dB typical. It is qualified for automotive applications and functions within an extended industrial temperature range of −40°C to +125°C.

Feature Summary

• Patented auto-zero topology eliminates 1/f noise and maintains low offset voltage drift over the operating lifetime.
• Rail-to-rail output capability maximizes signal-to-noise ratio by utilizing the full power supply range.
• Automotive qualification ensures reliability for demanding sensor and instrumentation environments.
• Low input bias current minimizes errors when interfacing with high-impedance signal sources.

Applications

• Pressure and position sensors
• Strain gage amplifiers
• Medical instrumentation
• Thermocouple amplifiers
• Precision current sensing

Procurement Notes

Verify the specific package variant against the ordering guide, as the WARZ suffix denotes a particular package configuration within the AD8639 family. Confirm that the automotive grade requirement aligns with the intended application environment. Ensure the design accommodates the specified input voltage range limits to prevent phase reversal or ESD diode conduction. Cross-reference the thermal resistance values for the selected package to validate heat dissipation requirements under maximum load conditions.

Selection Notes

Select this component when high DC precision and low drift are critical, particularly in systems requiring zero external filtering capacitors. Compare the 1.5 MHz bandwidth against system signal frequencies to ensure adequate settling time. Evaluate the trade-off between the low 1/f noise and the broadband switching noise inherent to auto-zero architectures. Consider the rail-to-rail output feature if maximizing dynamic range near the supply rails is necessary for the downstream ADC or processing stage.

Part Context

The AD8639 is part of Analog Devices' broader auto-zero operational amplifier series, which includes single-channel (AD8638) and quad-channel (AD8630) variants. These devices share a common patented ping-pong auto-zero and chopping topology designed to minimize low-frequency noise while maintaining high accuracy. The series targets applications previously reserved for expensive chopper-stabilized amplifiers, offering a cost-effective solution for precision measurement tasks across industrial and automotive sectors.

Replacement Considerations

Direct functional substitutes within the same family include the AD8638 for single-channel applications and the AD8630 for quad-channel configurations. Verify pin compatibility and package dimensions when replacing with other packages in the AD8639 series, such as SOIC or LFCSP variants, to ensure mechanical fit without redesigning the PCB footprint.

FAQ

Does the AD8639 exhibit output phase reversal?

No, the AD8639 is designed to prevent output phase reversal provided the inputs remain within the specified common-mode voltage range. If inputs exceed this range but stay within supply rails, the output may vary erratically due to internal loop opening.

How does the AD8639 handle overload recovery?

The AD8639 features a fast overload recovery time of less than 50 μs. This is achieved because internal settling occurs within two clock cycles after output saturation, significantly faster than many other auto-zero amplifiers.