Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Pass Labs This forum is dedicated to Pass Labs discussion.

FET as CCS in power supply?
FET as CCS in power supply?
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 7th July 2011, 06:51 PM   #1
Dr.H is offline Dr.H
diyAudio Member
Join Date: Apr 2002
Default FET as CCS in power supply?

Possibly a daft idea, but what would happen if a JFET was placed in CCS mode in between two caps in the initial ripple smoothing stage of a power supply? Would it lower the noise on the supply or accomplish anything good?
  Reply With Quote
Old 7th July 2011, 08:18 PM   #2
flg is offline flg  United States
diyAudio Member
flg's Avatar
Join Date: Jul 2005
Location: North East
Similar in theory to the Pi filter? An inductor between the 2 caps. The inductor is a current source, it resists the change of current.
"It was the perfect high end audio product: Exotic, inefficient, expensive, unavailable, and toxic." N.P.
  Reply With Quote
Old 7th July 2011, 08:44 PM   #3
sawreyrw is offline sawreyrw  United States
diyAudio Member
Join Date: Apr 2006
Location: Minnesota
The Idss of the FET must be larger than the load current, otherwise the output voltge will drop. This means that you can't really do what you want and the FET will be in cutoff. Note that the definitions of cutoff and saturation for a FET can be confusing. When a FET is in cutoff it really means it is "saturated" in BJT terms.
  Reply With Quote
Old 8th July 2011, 07:26 AM   #4
h_a is offline h_a  Europe
diyAudio Member
h_a's Avatar
Join Date: Sep 2006
Location: Graz, Austria
You essentially mean simple linear regulators (be it jfet, bjt or whatever); pretty common for small signal stages and usually prohibitively inefficient for power amps.

High Octane phono preamp Wiki
  Reply With Quote
Old 8th July 2011, 09:14 AM   #5
analog_sa is offline analog_sa  Europe
diyAudio Member
analog_sa's Avatar
Join Date: Aug 2002
Location: Cascais
Originally Posted by flg View Post
Similar in theory to the Pi filter?

The big difference between an inductor and a CCS is that the inductor has very low impedance at dc. A direct replacement is impossible.

Dr H's idea has some merit in particular situations and i have done something very similar in low current high voltage supplies. Imagine a tube rectifier feeding a giant capacitor through a CCS. Obviously the supplied circuit has to consume less current than the CCS but in effect you get a very high level of isolation from the mains and really low noise. At the same time you get very low PS impedance thanks to the giant electrolytic. At the time i used an EZ80 feeding a 3300uF and powering a phono pre. You can probably achieve similar technical performance in a more elegant way but i really liked the sound. Took almost an hour for the cap to reach operating voltage.

Not sure if this is useful in the context of power amps.
  Reply With Quote


FET as CCS in power supply?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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
PPI PC2400 OEM Power Supply FET? midnightg35x Car Audio 3 23rd March 2010 09:29 PM
CCS in Placid-BP Bipolar Shunt Regulated Power Supply Allen Wright Power Supplies 25 21st November 2009 08:41 PM
CCS power supply loading.. guitvinny Tubes / Valves 2 9th June 2008 05:50 AM
Aleph X Power Supply or FET boards??? batee Pass Labs 1 4th January 2006 07:28 AM
Problem identifying power supply FET R33_Cam Solid State 3 26th July 2004 10:22 AM

New To Site? Need Help?

All times are GMT. The time now is 02:12 AM.

Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio