New super pair? - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State

Solid State Talk all about solid state amplification.

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 31st December 2011, 01:45 AM   #1
diyAudio Member
 
Join Date: Nov 2007
Location: Dallas
Default New super pair?

Can such a simple trick nail MOSFET gate capacitance to a constant?
I have never seen an ESBT self-biased in this way before, is it new?
Can we now use MOSFET without squirming cap at stOOpid low VDS?

------

And a trio provides base current...
Attached Images
File Type: gif ESBT.gif (13.6 KB, 245 views)
File Type: gif ESBT2.gif (8.2 KB, 235 views)

Last edited by kenpeter; 31st December 2011 at 02:04 AM.
  Reply With Quote
Old 31st December 2011, 02:29 AM   #2
AKSA is offline AKSA  Australia
diyAudio Member
 
Join Date: Sep 2001
Location: Melbourne, Australia
Ken,

It's clever, but precisely what problem does it solve?

Hugh
__________________
Aspen Amplifiers P/L (Australia)
www.aksaonline.com
  Reply With Quote
Old 31st December 2011, 02:29 AM   #3
diyAudio Member
 
Join Date: Nov 2007
Location: Dallas
Source switched MOSFET? (optimally different types of course).
Attached Images
File Type: gif SSMF1.gif (8.6 KB, 229 views)
  Reply With Quote
Old 31st December 2011, 02:31 AM   #4
diyAudio Member
 
Join Date: Nov 2007
Location: Dallas
Quote:
Originally Posted by AKSA View Post
Ken,

It's clever, but precisely what problem does it solve?

Hugh
Unpredictable Miller capacitance at Low VDS.

Imagine the gate capacitance as-if an air bubble were squishing
back and forth from source to drain under a piece of Scotch Tape.
Situation I wish to avoid... Nothing against the Scotch.

Last edited by kenpeter; 31st December 2011 at 02:50 AM.
  Reply With Quote
Old 31st December 2011, 05:35 AM   #5
PRR is offline PRR  United States
diyAudio Member
 
PRR's Avatar
 
Join Date: Jun 2003
Location: USA
Working an FET with Drain below turn-on voltage puts you into a very different mode of operation, with soft "plate resistance" and lower and more-variable Gm.

In a sense, instead of squishy C skewing your highs you have squishy resistance parameters skewing everything.

Your Trio looks to me like a 3-stage amplifier which is liable to self-oscillate.

Have you tried these on breadboard?
  Reply With Quote
Old 31st December 2011, 07:29 AM   #6
godfrey is offline godfrey  South Africa
diyAudio Member
 
Join Date: Nov 2009
Location: Cape Town
Quote:
Originally Posted by kenpeter View Post
Can such a simple trick nail MOSFET gate capacitance to a constant?
I have never seen an ESBT self-biased in this way before, is it new?
I think base current will be a bitch with your first two self-bias circuits. The third one (with 2 MOSFETs) looks interesting, if you can get it stable.

Wouldn't it be easier just to use an ESBT as intended? You get almost constant voltage across the MOSFET. Judging from the pic below (swiped from a datasheet), it seems normal to run these things with very low Vds.

BTW, Nelson Pass mentioned awhile ago that he'd been playing with ESBTs. I wonder if anything interesting will come of that?
Attached Images
File Type: gif esbt.GIF (6.7 KB, 191 views)
  Reply With Quote
Old 2nd January 2012, 06:12 PM   #7
diyAudio Member
 
Join Date: Nov 2007
Location: Dallas
Quote:
Originally Posted by PRR View Post
Working an FET with Drain below turn-on voltage puts you into a very different mode of operation, with soft "plate resistance" and lower and more-variable Gm.

In a sense, instead of squishy C skewing your highs you have squishy resistance parameters skewing everything.

Your Trio looks to me like a 3-stage amplifier which is liable to self-oscillate.

Have you tried these on breadboard?
I'm not sure how the dynamic resistance of a cascode or ring of
two could be squishy? Gm might be reduced or curved or both...
Some curves are useful. If it turned out to be square law, that
might be a very good thing. Other curves, maybe not so useful.
But my magic eight ball don't tell me whats gonna happen.
Time to consult the entrails on a breadboard, or whatever...

Last edited by kenpeter; 2nd January 2012 at 06:17 PM.
  Reply With Quote
Old 2nd January 2012, 06:52 PM   #8
Bigun is offline Bigun  Canada
diyAudio Member
 
Bigun's Avatar
 
Join Date: Jan 2009
Blog Entries: 2
Looks interesting,


http://www.st.com/internet/com/TECHN...ivCta_2008.pdf

Look at the linearity in fig6
__________________
"The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed." Robert M Pirsig.
  Reply With Quote

Reply


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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Baxandall Super Pair peufeu Solid State 104 12th September 2012 10:40 AM
Origins of the Baxandall Super Pair? jez Solid State 22 30th December 2011 06:40 PM
Fs: pair of fostex t90a super tweeters tiverson Swap Meet 5 23rd October 2011 02:47 PM
FS: a pair of Fostex t900a super tweeters tiverson Swap Meet 2 28th February 2011 06:14 PM


New To Site? Need Help?

All times are GMT. The time now is 03:04 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2