BUF420M Current Sink - diyAudio
Go Back   Home > Forums > Amplifiers > Tubes / Valves

Tubes / Valves All about our sweet vacuum tubes :) Threads about Musical Instrument Amps of all kinds should be in the Instruments & Amps forum

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 12th September 2008, 10:06 PM   #1
diyAudio Member
 
Join Date: Aug 2005
Location: Seattle
Send a message via AIM to audiowize
Default BUF420M Current Sink

Hello all,
I'm trying to build a very large current sink as a type of inrush limiter. My idea was to use something along the lines of the BUF420M, grounding the emitter, setting up an adjustable voltage divider for the base, and pulling a couple hundred MA of current through the collector.

The plan is to use this between the ground and the CT on my power transformer, keeping the power supply somewhat confined. Any ideas? (320v B+)

Here is the data sheet:
http://www.st.com/stonline/books/pdf/docs/5063.pdf

What kind of voltage would you all expect across this guy? Any decrease in rectified B+? Best to bypass it with a cap?
  Reply With Quote
Old 13th September 2008, 03:10 AM   #2
diyAudio Member
 
tubelab.com's Avatar
 
Join Date: Jul 2005
Location: South Florida
Beware. All bipolar transistors suffer from a condition called "secondary breakdown". For most transistors this is the primary failure mode in linear operation. This limits the power dissipated by the device in linear mode. Most transistors have a chart showing the "SOA" (safe operating area) for several duty cycles and DC. These are not shown for this device. Only data for short pulse (.2uS). This device will probably die in your application.

I built a device similar to what you describe. I used a mosfet (no secondary breakdown) and drove it with the PWM output of a PIC chip. The pulse width is narrow at turn on gradually widening until the fet was fully turned on. A fully on fet drops about a volt in my system. You could do this with a 555 chip instead of the PIC chip.
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
  Reply With Quote
Old 13th September 2008, 03:16 AM   #3
diyAudio Member
 
Join Date: Aug 2005
Location: Seattle
Send a message via AIM to audiowize
Do you happen to have a schematic for your setup? So even if I'm running this guy conservatively (200ma) and not exposing it to high voltage, it will still break down?
  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
Any clue of how to use this part as a current sink for a CF? G Tubes / Valves 36 19th July 2006 07:35 AM
Does the PCM1794 sink or source current? Rescue Toaster Digital Source 0 17th September 2005 07:53 AM
Pentode current sink ABJ Tubes / Valves 14 23rd January 2005 09:56 PM
Using Ixys current regulator as current sink. G Solid State 3 16th November 2002 10:23 AM
Help with Current Sink RichardJones Pass Labs 1 31st January 2002 04:52 PM


New To Site? Need Help?

All times are GMT. The time now is 02:14 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