[sdiy] jfet driver

Mike Beauchamp list at mikebeauchamp.com
Wed Feb 27 01:19:50 CET 2019


> The question is, HOW LOW?  That depends on the JFET.  Some, like the 2N4391,
> are fairly unforgiving and will only reliably shut off when the Gate is held
> at about -10V or less.  It is best to take these right to the negative rail.
> Others, like the 2N5485 (which I see is now "obsolete" on Digikey -- too
> bad, it's a useful one) are more forgiving, and will "usually" shut off at a
> Gate voltage of about -4V.
Hi David,
Is the -10V shut off voltage for the 2N4391 the same as the "Voltage - 
Cutoff (VGS off) @ Id" characteristic?

If so I'm seeing N-Channel FETs on Digikey with a VGS(off) anywhere 
between 180mV and 10V.

Something like J106FS-ND has a VGS(off) of -2V typical and is through-hole.

Mike





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