Bias chain current for SAP16 - 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 19th November 2008, 03:11 PM   #1
cs is offline cs  United Kingdom
diyAudio Member
Join Date: Jun 2005
Location: .
Default Bias chain current for SAP16

The datasheet for the SAP16 temperature compensated darlington transistors recommends a bias current of 2.5mA down the diode biasing chain. In a practical power amp, this current would also flow through the VAS stage. But 2.5mA is quite low for the VAS, and I would normally use 2 or 3 times that.

Has anyone tried the SAP devices at higher bias chain currents, and if so, does the temperature compensation still work OK ?

  Reply With Quote
Old 19th November 2008, 03:18 PM   #2
AndrewT is offline AndrewT  Scotland
diyAudio Member
Join Date: Jul 2004
Location: Scottish Borders
the bias chain of diodes is ~ 5diodes + a variable resistor.
What voltage do you expect across this combination? Maybe 2.5V?
what parallel resistor would be required to pass the excess current through the VAS? Maybe 470r.
Leave a couple of extra pads to add one or two parallel resistors to trim the diode current once you get it running.
regards Andrew T.
Sent from my desktop computer using a keyboard
  Reply With Quote
Old 19th November 2008, 03:21 PM   #3
cs is offline cs  United Kingdom
diyAudio Member
Join Date: Jun 2005
Location: .
Hi Andrew,

Yes, that did occur to me, although I was concerned that the compensation effectiveness would be reduced.

  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
bias voltage vs bias current woodturner-fran Tubes / Valves 3 24th February 2007 11:24 PM
Bias and max current for my 7591 AB amp... mr mojo Tubes / Valves 14 6th January 2006 02:50 AM
LTP bias current cunningham Solid State 2 12th January 2005 08:39 PM
Bias current peter5 Solid State 6 13th January 2004 04:39 PM
BOZ Bias Current gema Pass Labs 2 20th February 2002 07:28 PM

New To Site? Need Help?

All times are GMT. The time now is 02:53 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