Matching at idle current - diyAudio
Go Back   Home > Forums > Amplifiers > Solid State
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

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
Thread Tools Search this Thread
Old 30th January 2012, 05:15 AM   #1
diyAudio Member
Join Date: Sep 2009
Location: Pretoria
Default Matching at idle current

I have a question. Why do many folks suggest matching at the amplifier's quiescent current. Doesn't the amount of current through parallel connected transistors vary with a load and signal?
Or am I understanding this the wrong way. Does matching at quiescent current, ensure linear, equal sharing throughout, regardless of load and signal level??
  Reply With Quote
Old 30th January 2012, 07:08 PM   #2
AndrewT is offline AndrewT  Scotland
diyAudio Member
Join Date: Jul 2004
Location: Scottish Borders
look at the Vbe vs Ic of a BJT.

Now look at a parallel pair of output BJTs.
For simplicity assume the base currents are the same.
What is the Vbe difference between the two output devices?

If one output device is selected randomly from the box and when connected up, it passes 1A of quiescent current and the other BJT passes 500mA of quiescent current from the same Vbe, then consider the operating temperature Tj of the two BJTs? Which one runs hotter?

Go back and look at the temperature effect on the Vbe vs Ic graph. Will the warmed up devices still be passing 500mA and 1000mA.
regards Andrew T.
Sent from my desktop computer using a keyboard
  Reply With Quote
Old 31st January 2012, 11:51 AM   #3
diyAudio Member
Join Date: Sep 2009
Location: Pretoria
Thanx Andrew!
Point well made!
  Reply With Quote


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
Audionet AMP 1 idle current chris86 Solid State 7 17th July 2013 03:34 PM
help setting up idle current lensmanMk2 Solid State 31 10th March 2010 11:48 PM
Idle current adjustment for NAD gvelim Solid State 0 5th August 2008 03:56 AM
XM-1502SX Idle Current sdoom Solid State 1 9th July 2004 07:35 AM
SMPS Idle Current cm961 Parts 2 20th February 2004 05:56 AM

New To Site? Need Help?

All times are GMT. The time now is 05:16 AM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2