[JN] VFET vs. Mosfet Vs. JFET

Grego Sanguinetti grego at sandesco.com
Tue Jan 13 11:39:37 CST 2009


jc morrison wrote:
> just to be clear, a VFET is not mos...
>   
Not clear at all, depends on your definition of MOS (or mos...).
VFET or VMOS devices can be built in a number of ways.
All of which include some sort of implanted oxidized channel structure.
In fact most small geometry CMOS processes built today (below 90nm) are 
vertical FETs and are by definition, MOS devices.
Of course the S in MOS is often replaced by GaAs, but is that really the 
issue?
As I recall, the SONY VFETs used a diffused silicon channel, so they 
were MOS by definition.

As to RF devices, I would watch out for 1/f noise. Most are not even 
characterized for it, much less optimized for it. I deal with that 
aspect of them in my day job.

Because of the isolated gate structure, JFETs make excellent low power 
audio devices, in both amplifier and switching applications.

I am out of touch with power FETs so won't comment there. I understand 
there are some GaAs VFETs available there but again, the 1/f noise may 
be an issue (or not).

-grego



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