Depletion Mode MOSFET'S and the VDmos Tool

[JWaugaman]

I've been looking for information on how to enter depletion mode MOSFET datasheet information in the LTspice VDmos Tool and came across the archived post by Hendrik Jan Zwerver from January 2007. The HelpPages Mostool.pdf document explains the use of the tool for enhancement mode MOSFET's, it has no information on using the tool for modeling depletion mode MOSFET's. For example, the Vgsth is negative as is the gate-source plateau voltage. Entering -3.5 for Vgsth and -2 for the gate-source plateau voltage resulted in an overflow error. What about the values of Vgs for entry in the Transfer Characteristics area? Strictly speaking, the Vgs values should be entered as appropriate for the type of MOSFET, that is, positive for enhancement mode devices and negative for depletion mode devices, but that doesn't seem to be the case.

It would be nice to have some guidance here rather than stumbling around trying various combinations hoping to find the right combination.

 

[Harald Kapp]

I don't know the tool you mentioned. However, Infineon is one of he no so many manufacturers making depletion MOSFETs. They have a description of their modeling here. And SPICE models for download here (you need to register, sorry).
Maybe by looking into the description and the models you can adapt or create your own model?