Safe T0 -92 case temperature? - 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 9th January 2009, 02:31 PM   #1
diyAudio Member
 
Join Date: Jan 2006
Location: Ireland
Default Safe T0 -92 case temperature?

Hi all,

A quick question to those who would know!!

I have some TO92 PNP and NPN transistors in a circuit. Types are BC550 and 560. My case temp is about 60 deg C. Junction temp is specd in the datasheet as 150 deg C.

Are my transistors too hot? Circuit functions perfectly.

(measurements taken in the case to reflect real life use etc. - tried searching and couldn't find anything on this)

Fran
  Reply With Quote
Old 9th January 2009, 02:36 PM   #2
Dr_EM is offline Dr_EM  United Kingdom
diyAudio Member
 
Dr_EM's Avatar
 
Join Date: Oct 2006
Location: Swindon
It might be worth adding something like this:

http://www.rapidonline.com/Electroni...Heatsink/77178

if the dissapation can't be reduced or the transistors changed. You can get metal can (TO18?) small signal devices and some that come in a sort of tall TO92 package.

I'm afraid I don't know if that is too hot though, I have never had a circuit where such devices become noticeably warm.
  Reply With Quote
Old 9th January 2009, 02:53 PM   #3
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi Woody,
what is the quiescent dissipation of your To92 devices?
What is the ambient temperature inside the closed casing?
What is the de-rating for the To92 device?
What is the peak dissipation?
Does the peak dissipation approach the de-rated dissipation?
Does the quiescent dissipation approach 50% of the de-rated dissipation?
__________________
regards Andrew T.
  Reply With Quote
Old 9th January 2009, 03:21 PM   #4
diyAudio Member
 
Join Date: Jan 2006
Location: Ireland
Eh, thats more questions than I have answers to!!!


I'll try and answer them as best I can, but I suppose if they're not melting in front of me then they're ok!

Fran
  Reply With Quote
Old 9th January 2009, 06:09 PM   #5
diyAudio Member
 
jacco vermeulen's Avatar
 
Join Date: Oct 2004
Location: At the sea front, Rotterdam or Curaçao
Send a message via Yahoo to jacco vermeulen
For thermal data of a TO-92 case, you can download the datasheet of an LM34DZ for example.
__________________
The buck stops Here
  Reply With Quote
Old 9th January 2009, 06:12 PM   #6
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Quote:
Originally posted by woodturner-fran
Eh, that's more questions than I have answers to!!!
quiescent device dissipation Pq = Iq * Vce.
Go and measure each device and multiply the numbers.
Come back with the results.
__________________
regards Andrew T.
  Reply With Quote
Old 9th January 2009, 06:38 PM   #7
diyAudio Member
 
Join Date: Jan 2006
Location: Ireland
mmm 20 devices on each board. will measure a few and come back with the data. Meanwhile a search on LM39dz (see jacco's post) says the max temp for it is 100 or 110degC.

Hopefully I'll be ok at 55. Will report more later.....

Fran
  Reply With Quote
Old 10th January 2009, 08:23 AM   #8
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
and out of the 20 off To92 devices, how many run at around 60degC?
__________________
regards Andrew T.
  Reply With Quote
Old 10th January 2009, 09:19 AM   #9
diyAudio Member
 
Join Date: Jan 2006
Location: Ireland
all of them - some a little cooler, but not by much. but essentially all at around 50-60 or so.

Fran
  Reply With Quote
Old 10th January 2009, 09:40 AM   #10
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
that's a lot of heat to dissipate inside this case.
20times 200mw to 300mW is going to cook everything.

Are you sure you are using the correct supply voltage?
__________________
regards Andrew T.
  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
Max safe operating temperature for transistors inside modified factory amplifier azzajonesy Solid State 8 8th October 2008 12:00 PM
Safe operating temperature. ronjodu Chip Amps 7 31st May 2007 12:11 AM
Is it safe???? mikee55 Solid State 4 31st August 2006 10:17 AM
Hakko 936 - ESD safe vs. non-ESD safe KT Parts 2 20th June 2004 03:58 AM


New To Site? Need Help?

All times are GMT. The time now is 05:12 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