low crossover-distortion class AB output stage topologies - Page 3 - 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 4th May 2011, 11:42 AM   #21
diyAudio Member
 
Edmond Stuart's Avatar
 
Join Date: Nov 2003
Location: Amsterdam
>Do you know any types?

Not in particular, sorry. But good candidates are the ones that have a rail to rail output capability.

Cheers,
E.
__________________
Een volk dat voor tirannen zwicht, zal meer dan lijf en
goed verliezen dan dooft het licht…(H.M. van Randwijk)
  Reply With Quote
Old 6th May 2011, 07:29 PM   #22
diyAudio Member
 
Join Date: Apr 2011
Location: Pretoria
This circuits also fascinates me.

But first - a short interruption. The author is Dutch. His first name is Wim and his surname is De Jager, not Jager. This translates into English as The Chaser, more or less.

Back to the circuit. Some of the devices, such as the matched pairs and output transistors used are now obsolete. Trying to simulate it is therefore a hassle as no models are to be found. I've tried...

However, I did manage to make a few substitutions and it works. The collector currents do indeed stay above zero, as advertised.

Here is my circuit with modern(!) devices and a plot of the collector currents in the output stage. It was done with LTspice IV. If there is any interest, I will post the LTspice file and the Spice models used.

The magic in this circuit lies in Q6, Q7, Q8 and Q9. Their base-emitter junctions form an uninterrupted loop, which makes it a translinear circuit. Through a bit of math, you come up with the equation

Ic6.Ic7 = Ic8.Ic9

With Ic8 related to Ic11 and Ic9 to Ic12, it becomes clear that they must all be non-zero for the above equation to hold. If anyone is interested, I can elaborate on the above math and on translinear circuits.

I would also like to know if this design has been used commercially. My guess is that it is not exactly cost efficient, as it uses a _lot_ of transistors for not a lot of watts. But then again, that should appeal to the flat earth brigade, hehehehe....
Attached Images
File Type: jpg DeJager99_circuit.jpg (66.3 KB, 630 views)
File Type: jpg DeJager99_collector_current.jpg (124.6 KB, 613 views)
  Reply With Quote
Old 16th May 2011, 09:51 PM   #23
diyAudio Member
 
Join Date: Apr 2011
Location: Pretoria
I think I have found the reason that the design never caught on. A Fourier analysis on LTspice shows a THD of about 0.3% - not exactly ground breaking. It may well be that TIM is quite good but I have not investigated that. The 'high' THD may be caused by both transistors being on all the time. In his book Douglas Self goes on about the perils of class AB. Perhaps this design falls into that trap and in trying to solve one problem (switching distortion) it makes another one worse. Does anybody have any thoughts on the matter?
  Reply With Quote
Old 16th May 2011, 09:57 PM   #24
jcx is offline jcx  United States
diyAudio Member
 
Join Date: Feb 2003
Location: ..
isn't that a little short in the current gain department? - beta enhanced VAS would have 2 more Q worth of gain - and still Cordell would recomend output triple
  Reply With Quote
Old 17th May 2011, 11:10 AM   #25
diyAudio Member
 
ostripper's Avatar
 
Join Date: May 2008
Location: Albany , NY (smallbany)
Here's one (below) . They last 20 years and sound real good. D701 / 703 are geraniums. These simulated well sub'ed with schottky diode's . Just 4 transistors makes for the Vbe and the non-switching OPS. Circuit idles OP's at about 10ma (never shuts them off - "krill like").

PS- I have the real thing to reverse engineer (actually 2 of them).

Another way to get low Xover is to use either a "fancy Vbe" or thermaltraks.

OS
Attached Images
File Type: gif nonswitching.gif (95.0 KB, 536 views)
__________________
Mongrel website , always current and updated :
http://www.fidelityforce.com/ostripper
  Reply With Quote
Old 17th May 2011, 11:21 AM   #26
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Geranium
Attached Images
File Type: jpg geranium.jpg (9.6 KB, 502 views)
__________________
If you don't change your beliefs, your life will be like this forever. Is that good news? - W S Maugham
Check out Linear Audio!
  Reply With Quote
Old 17th May 2011, 12:09 PM   #27
wahab is offline wahab  Algeria
diyAudio Member
 
Join Date: Nov 2009
Location: algeria/france
Quote:
Originally Posted by janneman View Post
Geranium
Are they from Germany ?...
  Reply With Quote
Old 17th May 2011, 07:30 PM   #28
diyAudio Member
 
Join Date: Apr 2010
Location: Coffs Harbour
__________________
regards
  Reply With Quote
Old 19th May 2011, 08:08 PM   #29
diyAudio Member
 
Join Date: Apr 2011
Location: Pretoria
Germanium transistors? Are those dinosaurs still around?
  Reply With Quote
Old 19th May 2011, 08:23 PM   #30
diyAudio Member
 
Wavebourn's Avatar
 
Join Date: Sep 2006
Location: Pleasant Hill, CA
Send a message via Skype™ to Wavebourn
Here you go.
Attached Images
File Type: gif Nuclon.gif (29.6 KB, 1098 views)
__________________
The Devil is not so terrible as his math model!
  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
CCS for PP Class A output stage? AudioGeek Tubes / Valves 5 24th January 2004 02:58 PM
Class A with AB Output-stage ManUtd Solid State 14 1st December 2003 05:49 PM
Class A output stage for CD Player PTSOUNDLAB Digital Source 0 30th December 2001 12:04 PM
Class h or g output stage? Opie Solid State 1 24th October 2001 09:30 PM


New To Site? Need Help?

All times are GMT. The time now is 12:28 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