Darlington or Mosfet? - 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 31st May 2010, 03:18 AM   #1
airboss is offline airboss  United States
diyAudio Member
 
Join Date: Apr 2010
Location: Reno, NV
Default Darlington or Mosfet?

Greetings:
I've stumbled over here from the Valve/Tube neighborhood because I can hardly wire a transistor to save my life.

Anyway, I have power transformers made for me for guitar amp projects with 12v filament windings. 4 amps. There are times when I would just as soon go DC on the filaments. So, with a cap input filter you get 17 volts. I would like to regulate that down to 12.6. Four amp regulators are ten or twelve bucks; when you can find them. So what's a good Darlington transistor that I can source 12V with a zener and multiply the current and not loose my 4.4 volts of headroom? Like this:
Click the image to open in full size.

The font is too small, I used paint to make this. Anyway, the base to emitter reverse diode is to protect the fragile E/B junction. I threw the other one in for spikes in the line. RS I have found, in spite of manufacturerers recommendations is usually arrived at experimentally. It's there to turn the 12V source zener on.

Anybody got a good number for one like this? Or am I going to have to go with Shotkey types with all the extra parts and doodads. I originally designed this for screen regulation and it works spiffy up in the 200VDC-300VDC range with the right transistor. I don't even know if they make 450V Darlingtons anymore. For screen supplies I used an NTE 2317

You know what? I just noticed this won't work unless one filament lead is grounded. I need a series device. Hmmmmmm. Lemme think. Maybe it will, just terminate the anode of the zener to the other filament line and lose the diode on the right? Like I say, I ain't too swift on these little gems.

Last edited by airboss; 31st May 2010 at 03:33 AM.
  Reply With Quote
Old 31st May 2010, 10:15 AM   #2
diyAudio Member
 
Join Date: Mar 2010
Location: Santiago, RS/ Brasil
Send a message via MSN to smartx21 Send a message via Skype™ to smartx21
Default Amplified zener

Hi!
Take a look here: Permanent Magnet DC Regulator
I used this configuration once in order to lower supply voltages in an AIWA power amplifier, with great success.
The attached one is to be used in series with positive rail. A slightly different configuration (with PNP BJT) can be used for negative supply.
But I can't see why use Darlington. Only a single NPN BJT will do the job. Be careful with heat, providing necessary sink.
Cheers,
Max.
Attached Images
File Type: gif amplified_zener.gif (1.3 KB, 123 views)

Last edited by smartx21; 31st May 2010 at 10:35 AM.
  Reply With Quote
Old 1st June 2010, 06:43 PM   #3
airboss is offline airboss  United States
diyAudio Member
 
Join Date: Apr 2010
Location: Reno, NV
Thanks Max, I'll have to look at some data sheets and see what the losses amount to. I could probably just put a couple of series diodes in the circuit to lose the extra volts. Filaments don't require regulation. They are sensitive to overvoltage.
  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
Pavel's MOSFET Follower - No Darlington Mod shaan Solid State 379 5th July 2010 05:25 AM
Darlington pair Tualek53 Parts 9 16th August 2005 07:54 AM
darlington/mosfet in emittor follower / headphone amp svokke Headphone Systems 11 8th June 2005 06:19 PM
Darlington and Triple darlington lumanauw Solid State 78 1st December 2004 12:57 AM
What is a darlington output exactly? mjarve Solid State 4 18th July 2004 01:28 AM


New To Site? Need Help?

All times are GMT. The time now is 10:55 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