AD8639ARMZ

Overview

The AD8639ARMZ is a dual-channel, wide-bandwidth auto-zero operational amplifier manufactured by Analog Devices Inc. It features rail-to-rail output swing and low noise characteristics. The device operates on a single supply of 5 V to 16 V or dual supplies of ±2.5 V to ±8 V. Key electrical parameters include a maximum offset voltage of 9 μV, an offset drift of 0.04 μV/°C, and a typical gain bandwidth product of 1.5 MHz. It offers high common-mode rejection ratio (CMRR) of 133 dB and power supply rejection ratio (PSRR) of 143 dB. The input bias current is typically 75 pA at 16 V operation. The component is housed in an 8-lead MSOP package.

Feature Summary

• Utilizes a patented ping-pong auto-zero topology that combines chopping and auto-zeroing to minimize low-frequency noise and digital switching artifacts without requiring external capacitors.
• Provides rail-to-rail output swing capability, allowing the signal to utilize the full dynamic range between the supply rails for optimal signal-to-noise ratio.
• Delivers ultrahigh precision with extremely low offset voltage and temperature drift, ensuring stable performance across the extended industrial temperature range.
• Features very low input bias current and eliminates 1/f noise internally, making it suitable for high-impedance sensor interfaces.

Applications

• Pressure and position sensors
• Strain gage amplifiers
• Medical instrumentation
• Thermocouple amplifiers
• Automotive sensors

Procurement Notes

Verify the specific ordering suffix against the manufacturer's official documentation to ensure correct package type and automotive qualification status. Confirm availability through authorized distributors as supply levels may fluctuate. Ensure the procurement channel provides valid traceability and authenticity guarantees for Analog Devices components.

Selection Notes

Select this component when high DC precision and low drift are required without the complexity of external filtering. It is appropriate for applications needing rail-to-rail output but does not support rail-to-rail input; inputs must remain within the specified common-mode range. Consider the 8-lead MSOP package constraints regarding thermal dissipation and PCB layout requirements.

Part Context

The AD8639 is part of the AD8638/AD8639 family of auto-zero operational amplifiers from Analog Devices. While the AD8638 is a single-channel version, the AD8639 provides two independent channels in the same technology node. This series is designed to offer the benefits of expensive zero-drift amplifiers at a lower cost point, targeting precision measurement systems.

Replacement Considerations

The AD8639ACPZ-REEL7 serves as a functional equivalent offering the same dual-channel specifications in an LFCSP package. The AD8639ARMZ-R7 provides identical electrical performance in a tape-and-reel format for automated assembly. Verify pinout compatibility and thermal characteristics when substituting packages.

FAQ

Does the AD8639 support rail-to-rail input?

No, the AD8639 is not a rail-to-rail input amplifier. The inputs must be maintained at least 2 V below the positive supply rail to prevent output phase reversal.

How does the AD8639 handle overload recovery?

The internal settling occurs within two clock cycles after output saturation, resulting in an overload recovery time of less than 50 μs.

What is the mechanism for eliminating 1/f noise?

The device uses auto-zeroing to correct DC and low-frequency offsets, effectively removing the 1/f noise component which appears as a slowly varying offset at the inputs.