Multiple transistor heat dissipation. - 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 22nd November 2011, 08:37 PM   #1
Boscoe is offline Boscoe  United Kingdom
diyAudio Member
 
Join Date: Feb 2010
Location: England
Default Multiple transistor heat dissipation.

If, for example, I have one transistor with a jc of 0.8C/W and a c-heatsink of 0.5C/W then and then a sink to air resistance of 0.5C/W I can dissipate 50W without exceeding a junction temp of 100C. If I now have two of the same transistor but now each dissipating 50W each is there an effective increase in junction to heatsink resistance or less now there are two paths for the heat to go? In other words is it more efficient to dissipate the same heat through multiple devices than one?

Thanks
Boscoe
__________________
I thought about it once, but then thought again.
  Reply With Quote
Old 22nd November 2011, 08:58 PM   #2
diyAudio Member
 
Join Date: Nov 2005
It's only an efficiency improvement in terms of maybe required heatsink size, but yes, adding parallel transistors decreases the total junction to ambient thermal resistance. You can run through the calculations to show how. Two transistors instead of one doubles die area and halves junction to case thremal resistance. So with a perfect sink it would take twice the power to raise the two junctions to the same temperature as one. Of course a real sink of fixed size is going to get hotter, so there's a diminishing return to be calculated.
  Reply With Quote
Old 22nd November 2011, 09:51 PM   #3
sreten is offline sreten  United Kingdom
diyAudio Member
 
Join Date: Nov 2003
Location: Brighton UK
Hi,

It is more efficient to to use two devices more than one as you effectively
half the resistance of the thermal paths. In fact for the same power two
devices need a smaller heatsink than one for the same junction temperature.

In reality keep the heatsink the same size (as one device) and up power say
30% (for two devices) to get the best out of the heatsinks and 2 devices.

rgds, sreten.
__________________
There is nothing so practical as a really good theory - Ludwig Boltzmann
When your only tool is a hammer, every problem looks like a nail - Abraham Maslow
  Reply With Quote
Old 22nd November 2011, 11:11 PM   #4
Tajzmaj is offline Tajzmaj  Slovenia
diyAudio Member
 
Join Date: Mar 2011
Location: Ljubljana
And something like 40-60W per device is safe and nice value.....
Best regards, Taj
  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
A3 heat dissipation problem spTOH Pass Labs 4 3rd October 2006 06:45 AM
Need help: 5687 tubes and heat dissipation Mrpong Tubes / Valves 6 20th March 2006 04:07 PM
CLC Question - Heat Dissipation TwangBar Pass Labs 2 2nd February 2005 09:01 PM
Heat dissipation from 3875 soundNERD Chip Amps 3 19th January 2005 02:03 AM
Heat dissipation Magura Pass Labs 26 15th November 2003 01:00 PM


New To Site? Need Help?

All times are GMT. The time now is 08:11 PM.


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