Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Pass Labs This forum is dedicated to Pass Labs discussion.

Distribution of Idss in a bunch of random 2SJ74?
Distribution of Idss in a bunch of random 2SJ74?
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
Reply
 
Thread Tools Search this Thread
Old 22nd November 2012, 01:54 PM   #31
bear is offline bear
diyAudio Member
 
bear's Avatar
 
Join Date: Apr 2002
Location: New York State USA
Hannes, see post #17... that is the difference in the parts I acquired between them and the original. Idss measured fine.
__________________
_-_-bear
http://www.bearlabs.com -- Btw, I don't actually know anything, FYI -- every once in a while I say something that makes sense... ]
  Reply With Quote
Old 23rd November 2012, 07:03 AM   #32
h_a is offline h_a  Europe
diyAudio Member
 
h_a's Avatar
 
Join Date: Sep 2006
Location: Graz, Austria
@bear:

Quote:
do you have a tip for us how to determine the transconductance "on the kitchen table"?
Transconductance is change in drain current for a given change in gate-source voltage; means measure IDSS (VGS=0) first, then insert a source resistor (VGS!=0) and measure ID. Divide the differences and you have an approximative transconductance value.

It's not so straight forward as transconductance depends a lot on the drain current, but this way should be sufficient to distinguish a genuine high transconductance jfet from a low transconductance part with both having the same IDSS.

Alternatively (but less practical), one could measure pinch-off voltage (when the jfet stops conducting), because that is very different also; for K170 it is about -1-2V VGS or so, for long channel low transconductance parts about -3-4 VGS or so.
__________________
High Octane phono preamp Wiki

Last edited by h_a; 23rd November 2012 at 07:27 AM.
  Reply With Quote
Old 23rd November 2012, 09:44 AM   #33
nr12 is offline nr12  Germany
diyAudio Member
 
Join Date: Mar 2011
Location: Schwaben
ok, thats easy to do.

As I have some genuine K170 to compare this is ok for me.

Thanks!
  Reply With Quote

Reply


Distribution of Idss in a bunch of random 2SJ74?Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Idss matched 2SK246 Y NYCOne Swap Meet 0 26th July 2011 10:03 PM
What is the correct Idss of jfet? Sunsun22 Parts 5 9th January 2011 12:31 PM
High Idss 2SK170GR? Sweetsweetback Parts 2 31st October 2010 11:40 PM
High Idss jFETs AndrewT Parts 24 30th October 2008 02:50 PM
Spice: how to set IDSS etc? bear Solid State 11 12th August 2005 02:20 PM


New To Site? Need Help?

All times are GMT. The time now is 07:23 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio
Wiki