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

Headphone Systems Everything to do with Headphones

Bias and stability
Bias and stability
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
Thread Tools Search this Thread
Old 26th July 2012, 09:19 AM   #1
Neutrality is offline Neutrality  Denmark
diyAudio Member
Join Date: Oct 2004
Location: Denmark
Default Bias and stability

In this circuit biasing is done with the four TO-126 transistors using the B-E diode stretch.

Bias stability is helped by the 10 Ohm Emitter resistors.

However, one could mount anywhere from 0 to 4 of the bias diodes on the same heatsinks as the output Q to get even better bias stability.

I usually like to work with Lateral FETs where bias stability is a non issue so any advice on bias stability of BJT's is much appreciated.

EDIT : Hmm, seems like this is similar to http://sound.westhost.com/project113.htm

EDIT : It looks like he does not have any of the 2 diodes he uses placed on the heatsink so I guess it is not really needed.
Attached Images
File Type: png Bragi_Biasing.png (32.6 KB, 90 views)

Last edited by Neutrality; 26th July 2012 at 12:25 PM.
  Reply With Quote
Old 27th July 2012, 05:46 PM   #2
nattawa is offline nattawa  Canada
diyAudio Member
Join Date: Apr 2010
Location: Mississauga, Ontario
3 diodes and you're over compensating, and 4 is way over what you need. You may want to leave the 4th off the heat sink to be sure of staying in class A and avoiding under biasing at higher temperature conditions.

I would not load the op amp up with a low-ish 750-ohm resistance and degrade the performance for nothing. A constant current source should be a good replacement for the R2 and R7 for me.
  Reply With Quote


Bias and stabilityHide 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
Output Power PP AB Stage - Value of Emitter Resistor for thermal Bias Stability tiefbassuebertr Solid State 1 30th November 2010 02:40 PM
Placid Stability steveww Twisted Pear 3 19th November 2010 07:25 PM
stability djdamix Solid State 3 7th January 2005 07:30 AM
symetric amp with mirrors, vas bias stability? Konrad Solid State 1 26th January 2004 06:07 PM
Aleph-X stability stefan Pass Labs 2 30th October 2002 09:00 PM

New To Site? Need Help?

All times are GMT. The time now is 02:02 AM.

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