SMP4118

Overview

The InterFET SMP4118 is an N-Channel Junction Field Effect Transistor (JFET) designed for ultra-high input impedance applications. It features a typical gate leakage of 120fA at 20V and a low input capacitance (CISS) of 1.8pF. The device operates with a gate-to-source breakdown voltage (BVGSS) of -40V minimum and a cutoff voltage range of -1 to -3V. Drain-to-source saturation current (IDSS) ranges from 0.08mA to 0.24mA, while forward transconductance (GFS) spans 80μS to 250μS. Available in SOT23 surface mount packages, it supports continuous power dissipation up to 350mW.

Feature Summary

• Ultra-low gate leakage current typically measured at 120fA
• Low input capacitance for high-frequency signal integrity
• High radiation tolerance suitable for demanding environments
• Interchangeable source and drain pins for flexible layout

Applications

• Signal mixers and buffers
• Radar and satellite communications systems
• Medical imaging and ultrasound monitors
• Femtoampere diode configurations

Procurement Notes

Verify the specific package variant required, as the SMP4118 designation covers both bulk and tape-and-reel options within the SOT23 form factor. Confirm compliance requirements such as RoHS and REACH status directly with the manufacturer or authorized distributor. Ensure that custom binning needs are addressed during the ordering process if specific electrical parameter tightness is required for the application.

Selection Notes

Select the SMP4118 when extremely low input bias currents are critical to circuit performance. The device offers a balance of moderate transconductance and very low capacitance, making it suitable for precision analog front ends. Consider the SOT23 package for space-constrained designs requiring surface mount technology. Evaluate thermal derating requirements if operating near maximum junction temperatures.

Part Context

The SMP4118 belongs to the 2N4117/A, 2N4118/A, and 2N4119/A family of N-Channel JFETs manufactured by InterFET. These components utilize proprietary InterFET N0001H geometry to achieve superior radiation hardness and low leakage characteristics compared to standard industry alternatives. The series provides multiple packaging options including through-hole TO-72/TO-92 and surface mount SOT23.

Replacement Considerations

Cross-reference models include SST4118, MMBF4118, 2N4118, and VCR7N. Verify pinout compatibility and electrical parameter overlaps before substitution. Note that while these parts share similar functions, specific leakage and capacitance values may vary between manufacturers.