N-Channel Enhancement Mosfet w/o reverse diode?

J

Jim Miller

Guest
I'd like to try an N-channel enhancement mode mosfet in a design that
requires low leakage. Hence I want a signal oriented device rather than one
designed for power use with a protection diode.

Any part numbers come to mind? Rds isn't critical but it would be nice to
have a relatively low Vgs(on).

tnx
jtm
 
Hi Jim,

Try in the very high frequency field, FETs for GHZ uses in preamps and
stuff like that. The bad news is that many of them including my old
favorites have been discontinued. If you do find one: These are hot
rods. One minor oversight in terms of input to output isolation and they
become an oscillator.

I could bet that experts like Winfield Hill would know a few that are in
production.

Regards, Joerg

http://www.analogconsultants.com
 
Jim Miller wrote:
I'd like to try an N-channel enhancement mode mosfet in a design that
requires low leakage. Hence I want a signal oriented device rather than one
designed for power use with a protection diode.

Any part numbers come to mind? Rds isn't critical but it would be nice to
have a relatively low Vgs(on).

tnx
jtm
Click to expand...
I don't know how small a device you are looking for or if you want
through hole or surface mount or what voltage rating, but here are
some possibilities:
(all from Digikey)

http://www.irf.com/product-info/datasheets/data/irld014.pdf
http://www.irf.com/product-info/datasheets/data/irlml2803.pdf
http://www.zetex.com/3.0/pdf/VN10LP.pdf


--
John Popelish
 
i've found a couple of p-channel devices that look pretty good if i can
design around them: 3N163 and 3N164.

these have reverse protection diode and picoamp gate leakage levels.

still like to find n-channel equivalents.

tnx
jtm
 
In article <vd2dnfG-jZ5vMcXcRVn-vw@comcast.com>,
Jim Miller <jim@removethisjtmiller.com> wrote:
I'd like to try an N-channel enhancement mode mosfet in a design that
requires low leakage. Hence I want a signal oriented device rather than one
designed for power use with a protection diode.

Any part numbers come to mind? Rds isn't critical but it would be nice to
have a relatively low Vgs(on).
Click to expand...
Try SST211.

I like them. They have 4 legs and are cute. What more could you ask for?

The substrate connection has to be more negitive than the source or drain
ever are. They are quite fast. 2nSis claimed but they seem to go faster
than that if the gate drive has very low impedance. Vgs(on) is only 1.5 so
it, I think, will meet the low voltage requirements.

The downsides of the SST211 are (1) they are easy to break and (2) the gm
is much lower than a power MOS-FET's.

--
--
kensmith@rahul.net forging knowledge
 
sst211 sounds interesting: who makes them?


Try SST211.

I like them. They have 4 legs and are cute. What more could you ask for?

The substrate connection has to be more negitive than the source or drain
ever are. They are quite fast. 2nSis claimed but they seem to go faster
than that if the gate drive has very low impedance. Vgs(on) is only 1.5 so
it, I think, will meet the low voltage requirements.

The downsides of the SST211 are (1) they are easy to break and (2) the gm
is much lower than a power MOS-FET's.

--
--
kensmith@rahul.net forging knowledge
 
On Mon, 27 Sep 2004 20:58:00 -0400, "Jim Miller"
<jim@removethisjtmiller.com> wrote:

sst211 sounds interesting: who makes them?


Try SST211.

I like them. They have 4 legs and are cute. What more could you ask for?

The substrate connection has to be more negitive than the source or drain
ever are. They are quite fast. 2nSis claimed but they seem to go faster
than that if the gate drive has very low impedance. Vgs(on) is only 1.5 so
it, I think, will meet the low voltage requirements.

The downsides of the SST211 are (1) they are easy to break and (2) the gm
is much lower than a power MOS-FET's.

--
Click to expand...
Look at Siliconix and Calogic. You might also consider an integrated
CMOS analog switch from Siliconix or Maxim.

John
 
no leakage specified on most of these parts and what is usually is in the nA
range. i'm looking for <pA.

actually the 3N163 is going to work fine!

thanks all

jtm (who ignored the tv show on and spent the evening geeking!)
 
Hi Jim,

Forgot to mention, check out these folks:

http://www.calmostech.com/products.html

They took over much of the hot rod FET arrays and singles. One of my
favorites is the four-pack SD5400 because they are nicely matched, low
leakage and fast. That one may not be the ticket for you in this case
but they've got a lot more.

Regards, Joerg

http://www.analogconsultants.com
 
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