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 14th October 2011, 05:53 PM   #1
diyAudio Member
 
Join Date: Oct 2004
Location: Aalborg, Denmark
Default Thermal compensation for BJT drivers with Lateral FET output

Do you need any thermal compensation for the drivers in an output stage with Lateral FETs?

Since the Laterals are thermally stable with just a resistor or resistor+pot in the vbe multiplier, thermal compensation for the BJT drivers should not be needed.

From what I can see from other designs with Lat FET output stages and BJT drivers, no thermal compensation seems to be needed.
  Reply With Quote
Old 14th October 2011, 06:03 PM   #2
mlloyd1 is offline mlloyd1  United States
diyAudio Member
 
mlloyd1's Avatar
 
Join Date: Feb 2001
Location: illinois
the original Hitachi data sheets & app notes (as well as old Hafler construction manuals) recommended 100mA per device quiescent current puts you pretty close to the zero tempco point for the lateral MOSFETs. If you do the same, you likely woon't need any fancy tempco circuitry.
  Reply With Quote
Old 14th October 2011, 06:56 PM   #3
Bensen is offline Bensen  Belgium
diyAudio Member
 
Bensen's Avatar
 
Join Date: May 2003
Location: Belgium, Limburg
My 2 cents,

I would not place the drivers on the main heatsink, this to avoid big temperature changes for the drivers.
I you place the drivers on a smaller heatsink and set the OPS bias after that the driver heatsinks reached a stable temperature, it should be fine. That's my experience.

Greetz
  Reply With Quote
Old 14th October 2011, 07:13 PM   #4
diyAudio Member
 
Join Date: Oct 2004
Location: Aalborg, Denmark
Quote:
Originally Posted by mlloyd1 View Post
the original Hitachi data sheets & app notes (as well as old Hafler construction manuals) recommended 100mA per device quiescent current puts you pretty close to the zero tempco point for the lateral MOSFETs. If you do the same, you likely woon't need any fancy tempco circuitry.
Was talking about the BJT drivers needing thermal compensation, not the Lateral FETs.
  Reply With Quote
Old 14th October 2011, 07:14 PM   #5
diyAudio Member
 
Join Date: Oct 2004
Location: Aalborg, Denmark
Quote:
Originally Posted by Bensen View Post
My 2 cents,

I would not place the drivers on the main heatsink, this to avoid big temperature changes for the drivers.
I you place the drivers on a smaller heatsink and set the OPS bias after that the driver heatsinks reached a stable temperature, it should be fine. That's my experience.

Greetz
That is good to know and more or less what I expected.
  Reply With Quote
Old 14th October 2011, 07:21 PM   #6
diyAudio Member
 
Michael Chua's Avatar
 
Join Date: Jul 2006
Location: Calais, ME
Quote:
Originally Posted by Neutrality View Post
Do you need any thermal compensation for the drivers in an output stage with Lateral FETs?

Since the Laterals are thermally stable with just a resistor or resistor+pot in the vbe multiplier, thermal compensation for the BJT drivers should not be needed.

From what I can see from other designs with Lat FET output stages and BJT drivers, no thermal compensation seems to be needed.
Yes, BJT drivers don't need any thermal compensation.
__________________
AmpsLab.com
  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
Biasing/thermal compensation of Thermal Trak transistors Bob Cordell Solid State 161 8th March 2014 08:42 AM
Lateral FET, Folded drivers, Biasing? Neutrality Solid State 2 27th August 2011 07:24 PM
Best drivers for BJT output stages Telstar Solid State 22 25th April 2010 01:37 AM
Advantage of a FET-BJT CCS vs BJT only Bitrex Tubes / Valves 2 10th June 2009 03:01 AM


New To Site? Need Help?

All times are GMT. The time now is 04:02 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