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

Solid State Talk all about solid state amplification.

Why collector/drain output stages are so rare???
Why collector/drain output stages are so rare???
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 18th December 2006, 01:08 AM   #1
Leolabs is offline Leolabs  Malaysia
diyAudio Member
 
Leolabs's Avatar
 
Join Date: Dec 2004
Location: Bukit Mertajam
Send a message via MSN to Leolabs
Question Why collector/drain output stages are so rare???

Is it because of stability issue???
  Reply With Quote
Old 18th December 2006, 08:12 AM   #2
vynuhl.addict is offline vynuhl.addict  Canada
diyAudio Member
 
vynuhl.addict's Avatar
 
Join Date: Mar 2006
Location: Vancouver, BC,Canada
If you mean FET outputs vs BJT doug self touches on this, not sure about others but he quaotes that fet outputs suffer from poor linearity and jagged crossover region compared to even the poorest BJT outputs..


Colin
  Reply With Quote
Old 18th December 2006, 10:17 AM   #3
richie00boy is offline richie00boy  United Kingdom
Did it Himself
diyAudio Member
 
richie00boy's Avatar
 
Join Date: Nov 2003
Location: Gloucestershire, England, UK
Why collector/drain output stages are so rare???
They are not really all that rare IMO. They can be harder to get right in class-b.
__________________
www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, modules and more.
  Reply With Quote
Old 18th December 2006, 10:29 AM   #4
lumanauw is offline lumanauw  Indonesia
diyAudio Moderator Emeritus
 
lumanauw's Avatar
 
Join Date: Oct 2002
Location: Bandung
Send a message via Yahoo to lumanauw
Do you mean CFP or something like SKA or MusicalFidelity uses?
  Reply With Quote
Old 18th December 2006, 11:00 AM   #5
edl is offline edl  Hungary
diyAudio Member
 
edl's Avatar
 
Join Date: Oct 2004
Default Re: Why collector/drain output stages are so rare???

Quote:
Originally posted by Leolabs
Is it because of stability issue???

QSC used this output topology.
Let's visit their site for schematics.

regards,
  Reply With Quote
Old 18th December 2006, 01:33 PM   #6
peranders is offline peranders  Sweden
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
Why collector/drain output stages are so rare???
Default Re: Why collector/drain output stages are so rare???

Quote:
Originally posted by Leolabs
Is it because of stability issue???
If you compare the properties between source out vs. drain out, I'll think you'll have the answer.

Most of the cases you want a low output impedance which you hardly will get if you have the drain as output.
__________________
/Per-Anders (my first name) or P-A as my friends call me.
Sign up for interest HERE. 4 pcb's in order. 0 paid.
  Reply With Quote
Old 18th December 2006, 06:27 PM   #7
Ultima Thule is offline Ultima Thule  Europe
diyAudio Member
 
Ultima Thule's Avatar
 
Join Date: Jan 2004
Location: PKS, Finland
Maybe as PerAnders wrote,

but on the ohter hand common emitter/source have much more gain added to the overall open loop which by the means of higher GFB rate also will add up to decrease output impedance/increase the damping factor where an all else equal common collector/drain will instead have initial lower output impedance and higher damping factor before the GFB is wrapped around, but also less open loop gain...

Gregs's (user Amplifierguru) is one example who have by now a well renoved amplifier design with his SKA proven to work well "despite" having a common soruce output stage.

I think it's a matter of implementation of both types, but I would as well like to hear especially from our heavy weighters what their views would be.

Cheers Michael
  Reply With Quote
Old 18th December 2006, 06:41 PM   #8
Ed Holland is offline Ed Holland  England
diyAudio Member
 
Join Date: Dec 2004
Location: Mountain View, California
Funny, I was thinking about this again recently, before this thread appeared.

If I recall correctly, the famous (in the UK at least) 50W amp kit sold by Maplin, had a common emitter topography. I'd always wondered about this, as nearly everything else is emitter-follower based. I reasoned that the designer was attempting either to increase open loop gain, or allow for local negaitive feedback in the o/p stage. However I can't find a copy of the schematic to check this out.

I built my first Hi fi amp from two of these modules, at age 17. I'm now 36 and still own and use that amplifier - it has a very clean sound and seems well behaved and "musical". However on one occasion, it did receive Swedish International Shortwave radio on 9 MHz. I was alerted (and startled) by the time signal, heard between tracks on the CD to which I was listening. The speaker leads seemmingly acted as antenae! Perhaps this pickup was an artefact of the common emitter circuit design, gain in the output stage?

Ed
  Reply With Quote
Old 18th December 2006, 06:55 PM   #9
Wavebourn is offline Wavebourn  United States
Designer & Technologist
diyAudio Member
 
Wavebourn's Avatar
 
Join Date: Sep 2006
Location: Pleasant Hill, CA
Why collector/drain output stages are so rare???
Default Re: Why collector/drain output stages are so rare???

Quote:
Originally posted by Leolabs
Is it because of stability issue???
Fashion from one side, belief that CC is simplier from another side. Also, a lot of designers don't think of linearity of current amplification and stuck to voltage amplifications, even when call own amps POWER amps, not VOLTAGE amps. Emitter followers seem to amplify voltage more linear (however, when no current is drawn by a load).

__________________
Nothing in the universe is perfect. The ideal things are the ones that are most optimal. Optimization criteria, what matters. When I hear "No Compromise Design", I want to take a sledgehammer and test how impact-proof it is.
  Reply With Quote
Old 18th December 2006, 06:56 PM   #10
pixpop is offline pixpop  United States
diyAudio Member
 
pixpop's Avatar
 
Join Date: Jan 2005
Location: Los Angeles
Why collector/drain output stages are so rare???
I just assumed it was because of Miller effect. Is that not the case?
  Reply With Quote

Reply


Why collector/drain output stages are so rare???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
Common Source versus Common Drain output stages alaskanaudio Solid State 36 1st June 2014 02:35 AM
Open collector npn output marjan Solid State 5 15th January 2005 06:40 PM
cheap output stages hacknet Solid State 0 8th December 2002 01:55 PM


New To Site? Need Help?

All times are GMT. The time now is 07:46 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki