[sdiy] Vco I did today...

[patchell]

    Yes, but the 2n4391 is a bit on the pricey side...still, I will have to
endevor to do some tests to see if I can measure any difference between the
two.  On a casual basis, I have not noticed any performance differences between
the J111 and the 2n4391 (I have both parts, so I can use both in the exact same
circuit, keeping the number of variable changes to a minimum).  I am also going
to see if I can come up with a good way to measure the channel leakage.  I am
curious if there is a real difference, or if the spec was looser so that more
parts could potentially pass test...(nothing like depending on typical
performance to make your life exciting...eh?).

Ian Fritz wrote:

> If you look at the comparison chart given by Farichild, you will see that
> 25 different parts come from that one process (No. 51).  Most are not all
> that suitable for the sawtooth VCO application.  I think the best devices
> are the 2N4391, 2N4859, 2N4091 (all from process 51) and the2N5432 (process
> 58). To me, the J111 has too much leakage and too little pass current.  A
> couple of weeks ago I looked around and found that three manufacturers are
> still producing the 2N4391, which is my choice for the best unit.
>
>    Ian
>
> At 12:00 PM 1/16/2003, Tim Ressel wrote:
> >Jim,
> >
> >I don't think the J111 and 2N4391 are the same. J111
> >shows 1nA Idoff, 2N4391 is 0.1nA.
> >
> >You're right, Rdson and Idoff tend to be exclusive.
> >But it makes sense; the combination can be thought of
> >as the dynamic range of the FET. The question I have
> >is: which is more important, Rdson or Idoff?
> >
> >--tr
> >
> >--- patchell <patchell at silcom.com> wrote:
> > >     I have had no problems with them.  The J111 is
> > > equiv (well, actually
> > > the same die as) the 2n4391 which has also been used
> > > a lot.

--
 -Jim
------------------------------------------------
* Visit:http://www.silcom.com/~patchell/
*-----------------------------------------------
*I'm sure glad Merry Christmas comes just once a year
* -Yogi Yorgensen
------------------------------------------------