2SK191 - anyone ever seen one?

scott wurcer · 15th June 2007, 06:39 PM

I found a site with a comprehensive list of Japanese JFETs, many probably obsolete or unavailable. But this one caught my eye, typ. gm of 100mS! and Idss that would burn it out. It came in the elongated TO plastic package like the fabled early Toshiba parts. I figure .32nV/rt-Hz with a single device.

jacco vermeulen · 15th June 2007, 07:22 PM

"elongated" as in the tall hat TO92 case, you mean.
Hitachi stuff, were used in some SSB receivers.

(the most frequent request a yachtsman and an electronic turd gets is to repair a boat radio, on the cheap of course)

StevenOH · 16th June 2007, 12:33 AM

<<I figure .32nV/rt-Hz with a single device>>

This is what I have calculated too. But datasheet shows en leveled (minimum) at 0.5nV/rt-Hz at 8-10 mA, 1 KHz, 10V...
Compare to Interfet low noise FETs.

scott wurcer · 18th June 2007, 01:06 PM

Quote:

Originally posted by StevenOH
<<I figure .32nV/rt-Hz with a single device>>

This is what I have calculated too. But datasheet shows en leveled (minimum) at 0.5nV/rt-Hz at 8-10 mA, 1 KHz, 10V...
Compare to Interfet low noise FETs.

Couldn't find a complete datasheet, higher current operation is problematic (though I wonder if you get to .35nV at 40mA) and maybe there is some parasitic resistance (you don't need much).

In still pretty up on the BF862 (0.15$) from Philips, Jim Williams put me on to it. 1nV at 8pF, it's only speced for RF but I finally got around to measuring the corner frequency at below 100Hz. A random sample I picked had <1pA Ib too.

jacco vermeulen · 18th June 2007, 01:39 PM

Regular price for a BF862 is close to $0.50/pc overhere, at a few thousand around $0.20 each.
The 50 pieces for $6.95 sounds more like Mr Florida on Ebay.

Bit fast example maybe, but seen THIS by Linear.

scott wurcer · 18th June 2007, 03:02 PM

Quote:

Originally posted by jacco vermeulen

The 50 pieces for $6.95 sounds more like Mr Florida on Ebay.

Bit fast example maybe, but seen THIS by Linear.

Sorry yes, but isn't that the first place you look?

Jim's circuit was a little different but super clever (a real "why didn't I think of that 15yrs. ago"). Of course he didn't either.

jacco vermeulen · 18th June 2007, 03:20 PM

Mr Wurcer,

mea culpa, not the smartest thing to say to an opamp biggy from Analog.
The post was meant as an illustration, not directly adressed to you.
I'll be back after a bit of banging my head against the wall for the next hour.

15th June 2007, 06:39 PM	#1
scott wurcer diyAudio Member Join Date: Jan 2004 Location: cambridge ma	2SK191 - anyone ever seen one? I found a site with a comprehensive list of Japanese JFETs, many probably obsolete or unavailable. But this one caught my eye, typ. gm of 100mS! and Idss that would burn it out. It came in the elongated TO plastic package like the fabled early Toshiba parts. I figure .32nV/rt-Hz with a single device. __________________ 2012, our time is running out.

15th June 2007, 07:22 PM	#2
jacco vermeulen diyAudio Member Join Date: Oct 2004 Location: At the sea front, just under Rotterdam	"elongated" as in the tall hat TO92 case, you mean. Hitachi stuff, were used in some SSB receivers. (the most frequent request a yachtsman and an electronic turd gets is to repair a boat radio, on the cheap of course) __________________ Looks like Sponge Bob has killed another thread.

18th June 2007, 01:39 PM	#5
jacco vermeulen diyAudio Member Join Date: Oct 2004 Location: At the sea front, just under Rotterdam	Regular price for a BF862 is close to $0.50/pc overhere, at a few thousand around $0.20 each. The 50 pieces for $6.95 sounds more like Mr Florida on Ebay. Bit fast example maybe, but seen THIS by Linear. __________________ Looks like Sponge Bob has killed another thread.

18th June 2007, 03:20 PM	#7
jacco vermeulen diyAudio Member Join Date: Oct 2004 Location: At the sea front, just under Rotterdam	Mr Wurcer, mea culpa, not the smartest thing to say to an opamp biggy from Analog. The post was meant as an illustration, not directly adressed to you. I'll be back after a bit of banging my head against the wall for the next hour. __________________ Looks like Sponge Bob has killed another thread.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

16th June 2007, 12:33 AM	#3
StevenOH diyAudio Member Join Date: Jun 2004 Location: USA	<<I figure .32nV/rt-Hz with a single device>> This is what I have calculated too. But datasheet shows en leveled (minimum) at 0.5nV/rt-Hz at 8-10 mA, 1 KHz, 10V... Compare to Interfet low noise FETs.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read