U440

Overview

The U440 is a matched N-Channel JFET pair featuring a two-chip design within a hermetically sealed TO-71 package. It provides a gate-source cutoff voltage range of -1 to -6 V and a minimum forward transconductance of 4.5 mS. The device ensures tight matching with a maximum differential gate-source voltage of 10 mV and offers low gate leakage of 1 pA typical. It supports an operating junction temperature from -55°C to 150°C.

Feature Summary

• Two-chip monolithic design for reduced parasitics and high-frequency performance
• Hermetically sealed TO-71 package suitable for military screening
• Extremely tight matching between paired JFETs
• Low offset and drift voltage characteristics

Applications

• Wideband differential amplifiers
• High-speed comparators
• Impedance converters
• High-speed, temp-compensated single-ended input amps

Procurement Notes

Verify the specific lot code and manufacturing date against current availability as this component may be subject to discontinuation or lifecycle changes. Confirm that the TO-71 package form factor aligns with existing board layouts. Ensure procurement channels provide documentation regarding MIL-S-19500 screening if military-grade reliability is required for the application.

Selection Notes

Select the U440 when precise matching between dual JFETs is critical for circuit performance. Consider its hermetic sealing for harsh environments where standard plastic packages are unsuitable. Evaluate the -1 to -6 V cutoff voltage range to ensure compatibility with the intended biasing network. Verify that the TO-71 footprint matches the target PCB design constraints.

Part Context

This component belongs to Vishay Siliconix's lineup of matched JFET pairs. It serves as a direct replacement for discontinued Siliconix U440 units. For applications requiring SO-8 packaging, the SST440/SST441 series is available. Low-noise alternatives include the SST/U401 series, while low-leakage options are found in the U421/423 data sheet.

Replacement Considerations

The U440 is explicitly identified as a direct replacement for discontinued Siliconix U440 devices. Designers should verify pinout compatibility and thermal characteristics when substituting legacy parts.