[JN] VFET vs. Mosfet Vs. JFET

bear bear at bearlabs.com
Sun Jan 11 16:10:02 CST 2009


> Ahhh... I love acronyms....
> Well the Phemts I have worked with where GaAs...
> I have worked them (still in RF) down to 5MHz, and the Noise just keeps
> dropping.
> Main disadvantage as I see it is, that they will fry in an instance if
> they
> see more than 35V on the gate (I have seen them fry by the build up
> capasitance of 2 feet of coax cable).
> Still, they handle a relativly high amount of power in a liniar way, and
> their added noise is neglible so could be a fun experiment...
> Heck, I should just go try it...
> maybe I should try with some SiGe types first...Not as liniar or quiet,
> but
> a lot more robust....

The usual application is on the front end of an amp, preamp or MC phono
stage... so power or higher voltages are not usually a consideration.


>
> Happy tinkering!
> Kåre
>
>
>
> On Sun, Jan 11, 2009 at 9:03 PM, bear <bear at bearlabs.com> wrote:
>
>>
>> > On another (related) note.
>> > Has anyone here ever tried using PHEMT devices for audio?
>> > I have an old dream of trying a MC riaa with these as frontends. they
>> > should
>> > be great on noise if they can be tamed (GHz devices).
>>
>> That's "Can't Remember S...t"
>>
>> Or "can't remember stuff"
>>
>> PHEMT, aren't they RF devices?
>> Don't know if they are quiet in LF or not.
>>
>> GasFets might be interesting too...but again dunno their LF noise
>> figures...
>>
>>              _-_-bear
>>  >
>> > Any comments?
>> >
>> >  Just out of curiosity...what does CRS mean in this context?
>> > Is it one of these:
>> > http://acronyms.thefreedictionary.com/CRS
>> >
>> > /Kåre
>> >
>> > On Sun, Jan 11, 2009 at 7:29 PM, bear <bear at bearlabs.com> wrote:
>> >
>> >>
>> >> The VFET is a special device, it is different than either the JFET or
>> >> the
>> >> Mosfet. Also known as the Vertical FET, it refers to the way the
>> >> structure
>> >> is made on the silicon die. Because of the different technique it is
>> >> both
>> >> problematic to make, (or was) and it resulted in different
>> >> characteristics
>> >> compared to the Mosfet (much easier to make).
>> >>
>> >> I think that the VFET gave triode like curves, whereas the Mosfet
>> >> definitely gives pentode like curves. both result in devices that can
>> >> handle power, unlike the JFET that is rather fragile by comparison...
>> >>
>> >> I don't recall if Siliconix made VFETs or not, but I was under the
>> >> impression that the VFETs used by SONY and Yamaha were made in
>> Japan...
>> >>
>> >> I've studied them in some detail, and have texts that go into detail
>> on
>> >> all this, but due to CRS, I don't recall very much detail.
>> >>
>> >>
>> >>
>> >> _-_-bear
>> >>
>> >> http://www.bearlabs.com
>> >> BEAR Labs
>> >>
>> >> _______________________________________________
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>> >> Sound at mailman.soundlist.org
>> >> http://mailman.soundlist.org/mailman/listinfo/sound
>> >>
>> >
>>
>>
>> _-_-bear
>>
>> http://www.bearlabs.com
>> BEAR Labs
>>
>>
>


_-_-bear

http://www.bearlabs.com
BEAR Labs




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