AD8684ARZ

Overview

The AD8684ARZ is a quad low power, high speed JFET operational amplifier manufactured by Analog Devices. It features a typical gain bandwidth product of 3.5 MHz and a slew rate of 9 V/µs. The device operates within a supply voltage range of ±4.5 V to ±18 V (or single supply 9 V to 36 V). Key electrical characteristics include a maximum offset voltage of 1 mV at 25°C, a maximum input bias current of 20 pA at 25°C, and a typical common-mode rejection ratio of 90 dB. Supply current per amplifier is typically 210 µA with a maximum of 250 µA. The component is housed in a 14-lead SOIC_N package.

Feature Summary

• JFET input stage ensures extremely low input bias current and high input impedance.
• Unity-gain stable design allows for direct buffering applications without oscillation risks.
• Optimized for high-speed performance while maintaining very low quiescent power consumption.
• Wide common-mode input voltage range includes the positive supply rail.

Applications

• Portable telecommunications equipment
• Low power industrial and instrumentation systems
• Active and precision filters
• Strain gauge amplifiers
• Supply current monitoring circuits

Procurement Notes

Verify the specific ordering suffix against the manufacturer's official documentation to confirm packaging options such as tube or reel configurations. Ensure the RoHS compliance status matches project requirements, as indicated by the 'Z' suffix in the part number. Cross-reference the thermal resistance values for the 14-Lead SOIC_N package during PCB layout planning to ensure adequate heat dissipation under maximum operating conditions.

Selection Notes

Select this component when application requirements demand a combination of high slew rate and low power consumption. The JFET input architecture makes it suitable for high source impedance environments where bias currents must be minimized. Verify that the required supply voltage falls within the specified ±4.5 V to ±18 V range and that the operating temperature aligns with the -40°C to +85°C specification.

Part Context

The AD8684ARZ belongs to the AD8682/AD8684 family of dual and quad low power, high speed JFET operational amplifiers. This series is designed to provide excellent dynamic response and DC precision at low quiescent currents. The quad configuration offers space savings compared to using multiple dual amplifiers, making it ideal for dense circuit board layouts in portable and battery-powered devices.

Replacement Considerations

The AD8682ARZ serves as the dual-channel equivalent within the same family. Other variants in the series include AD8684ARZ-REEL and AD8684ARUZ for different packaging needs.

FAQ

Does the AD8684ARZ experience phase inversion?

Yes, if the input signal exceeds the common-mode range, specifically causing a negative signal in excess of 11 V, the input stage may saturate and forward-bias a gate-drain diode, leading to phase reversal.

What is the maximum input bias current over the full temperature range?

While the maximum input bias current is 20 pA at 25°C, it increases to a maximum of 125 pA over the full operating temperature range of -40°C to +85°C.