Pedja Rogic discrete regulator question - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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 22nd July 2012, 10:13 AM   #1
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
Default Pedja Rogic discrete regulator question

Next to the SMPS, my favourite power supply for chip amps is the Pedja Rogic discrete regulated. I've just built another pair of these regulators, and they appear to work OK but I have a question about the measured voltages.

I'm using BZX55 C27 zeners (500mW) that are quoted as having a voltage between 25.1 and 28.9. However, in my case I am getting voltages of 29.5, 29.8 29, and 29.4, all above the maximum quoted in the datasheet.

The corresponding output voltages are: 27.1, 27.3, 27.3, 27.4 - so would appear to be what is expected from the diode voltages.

My question is - are these diodes just a little bit out of spec, or is there something wrong with my circuit?

Click the image to open in full size.
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.

Last edited by Nuuk; 22nd July 2012 at 10:15 AM. Reason: To add circuit diagram
  Reply With Quote
Old 22nd July 2012, 03:42 PM   #2
diyAudio Member
 
Juergen Knoop's Avatar
 
Join Date: Jan 2007
Blog Entries: 3
hard to say...the zeners voltages depend on their operating current which is set by R1/R2. Those resistors have to match the FET parameter spreads.
The larger the oprerating current the larger the zener voltage. So to which current you've set the current sources to?
  Reply With Quote
Old 22nd July 2012, 04:38 PM   #3
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
Quote:
Originally Posted by Juergen Knoop View Post
hard to say...the zeners voltages depend on their operating current which is set by R1/R2. Those resistors have to match the FET parameter spreads.
The larger the oprerating current the larger the zener voltage. So to which current you've set the current sources to?
I've got between 7.4 and 7.6 mA to all for J309's (as Pedja recommends).
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  Reply With Quote
Old 22nd July 2012, 05:30 PM   #4
diyAudio Member
 
Juergen Knoop's Avatar
 
Join Date: Jan 2007
Blog Entries: 3
you could try 5mA at one diode as specified in the datasheet. Thus you would know!
  Reply With Quote
Old 22nd July 2012, 05:32 PM   #5
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
Quote:
Originally Posted by Juergen Knoop View Post
you could try 5mA at one diode as specified in the datasheet. Thus you would know!
Thanks, I'll try it.
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  Reply With Quote
Old 22nd July 2012, 06:31 PM   #6
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
5mA brings the voltage down about half a volt so it's still a bit on the high side. I've got to go out now but will lower it further when I get time.
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  Reply With Quote
Old 22nd July 2012, 06:41 PM   #7
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
Alternatively, how about using some BZX85/27 diodes?

BZX85 pdf, BZX85 description, BZX85 datasheets, BZX85 view ::: ALLDATASHEET :::
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  Reply With Quote
Old 23rd July 2012, 09:37 PM   #8
diyAudio Member
 
Juergen Knoop's Avatar
 
Join Date: Jan 2007
Blog Entries: 3
Seems the zeners are indeed inside their specified parameter range. Using other types won't help you very much, since they have an app. ten percent range as well. Anyway those simple regs tend to sag under load, so they would never be 'DC accurate'.
Luckily the chipamp doesn't care about volt more or less!
  Reply With Quote
Old 23rd July 2012, 09:47 PM   #9
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
Well it's been fun (and educational) trying different zeners and changing R1/R2. I must look in the original modules that I built as I have ~25 volts on all the outputs with them.

I'll soon be comparing these Pedja Regs against the SMPS supply (both amps use LM3875's).
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  Reply With Quote
Old 26th July 2012, 01:35 PM   #10
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
The BZX85/27 diodes arrived this morning, are fitted, and it all measures as it should so I would suggest that anybody building the Pedja regs uses those (in conjunction with 150R for resistors R1/R2.
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  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
Pedja Rogic´s Discrete Diamond Non-Feedback I/V Stage for TDA1541A dvb projekt Group Buys 14 1st April 2013 05:50 PM
Pedja Rogic JFET or Nelson Pass B1? regiregi22 Analog Line Level 3 17th January 2010 02:35 AM
Pedja Rogic buffer + pllxo joshuajoshua Chip Amps 0 31st January 2009 05:32 AM
WTB: Pedja Rogic buffer board vizion Swap Meet 0 16th May 2008 03:49 PM
FS: Pedja Rogic Rev.1 DAC, mostly propagated Strohmie Swap Meet 4 27th August 2007 07:49 PM


New To Site? Need Help?

All times are GMT. The time now is 04:58 AM.


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