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Can I Determine Vth for a MOSFET From a Curve Tracer? - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues. Original posts:

Amateur Radio | Antennas | Circuits & Components | Systems | Test & Measurement

Post subject: Can I determine Vth for a MOSFET from a Curve Tracer? Posted: Thu Feb 05, 2009 11:13 am


Joined: Mon Apr 10, 2006 12:43 pm
Posts: 25
Good day. This might be a very simple question but I am stuck.

I have setup a curve tracer simulation within SPICE (LTSPICE from Linear Technology). I am just using the generic MOSFET model that comes with LTSPICE.

How can I determine the threshold voltage from the output of the curve tracer?

LTSPICE does allow me to export the data from the curve tracer plot into a form that I can import into an Excel Spreadsheet.

Any suggestions and/or reference material would be greatly appreciated.



Post subject: Re: Can I determine Vth for a MOSFET from a Curve Tracer?Posted: Thu Feb 12, 2009 3:59 pm

Site Admin

Joined: Mon Jun 27, 2005 2:02 pm
Posts: 373
Location: Germany
Hello Michael,

I don't use this kind of Spice. But in general I would say that for MOSFET (Depletion or Enhancement), Vth is the point at which the current starts to ramp up rapidly.

Here is a picture to demonstrate:

Hope this helps!

Best regards,

- IR


Post subject: Re: Can I determine Vth for a MOSFET from a Curve Tracer?Posted: Fri Feb 13, 2009 10:56 am


Joined: Mon Apr 10, 2006 12:43 pm
Posts: 25
Good day IR.

Thank you very much for the answer and the link.


Posted  11/12/2012

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