JFET's

[Bjoern Starmark]

Steven, 

1.For specs on JFET's, you should check out Temic's home page:

http://www.temic.com

This is the site where Siliconix's products are hiding, took me months
of active searching to find it out! You'll find data sheets on many
JFET's here. 

2.A quick look in my data books reveals that the 2n4391 migth be a good
choice. A comparison between Siliconix 2n4391, 2n4392 and NS 2n4859
(obsolete) shows:

JFET	Vgs(off) (V)	rds(on) (ohm)	Id(off) (pA)	ton (ns)

2n4859	-10		25		250		8
2n4391	-10		30		100		15	
2n4392	-5		60		100		15

The 4391 and 4392 trades low off leakage (IDoff) to somewhat higher
channel on resistance (rds(on)) and the double turn-on time (ton), when
compared with the 4859.

I'd go for the 4391, unless the 4392 is considerably cheaper. I don't
know about the other ones you mentioned...

Bjorn