bipolar (bjt) transistor families for audio power output stages - Page 9 - 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 18th December 2009, 01:55 PM   #81
Eva is offline Eva  Spain
diyAudio Member
 
Eva's Avatar
 
Join Date: Oct 2003
Location: Near the sea
Send a message via MSN to Eva
Could you explain the physical diferences between a "switching die" and an "audio die" in bipolar transistors?

I don't get it.

Also, in my opinion bipolar transisros work better in switching applications when:

- They keep good current gain up to high current levels, so that not a too high base current is required to achieve a low saturation Vce
- Capacitances are low, capacitances are evil in switching applications (losses, parasitic turn on, etc...)
- Transition frequency is high, which tends to imply quick saturation and de-saturation, the opposite of storing huge charge in the junctions

In fact, I think the Japanese audio bipolar transistors could be great for switching too...
__________________
I use to feel like the small child in The Emperor's New Clothes tale

Last edited by Eva; 18th December 2009 at 02:00 PM.
  Reply With Quote
Old 18th December 2009, 02:53 PM   #82
diyAudio Member
 
bobodioulasso's Avatar
 
Join Date: May 2008
The Semi South jfets are made for switching applications. And they are excellent in audio.
  Reply With Quote
Old 18th December 2009, 03:12 PM   #83
Banned
 
Join Date: Apr 2005
Location: Stockholm
bobodioulasso,
Quote:
The Semi South jfets are made for switching applications. And they are excellent in audio.
Right. Video transistors made for CRT screens are the very best you can use in VAS, but there s much more to say about this issue. In short, you need to choose the devices with extreme care.
  Reply With Quote
Old 18th December 2009, 03:24 PM   #84
diyAudio Member
 
jan.didden's Avatar
 
Join Date: May 2002
Location: Great City of Turnhout, Belgium
Blog Entries: 7
Quote:
Originally Posted by Lumba Ogir View Post
bobodioulasso,

Right. Video transistors made for CRT screens are the very best you can use in VAS, but there s much more to say about this issue. In short, you need to choose the devices with extreme care.
Video transistors often have very low gain and very non-linear Ic/Vce curves. Choosing with care also means not to generalize.

jd
__________________
I won't make the tactical error to try to dislodge with rational arguments a conviction that is beyond reason - Daniel Dennett
Check out Linear Audio Vol 7!

Last edited by jan.didden; 18th December 2009 at 03:31 PM.
  Reply With Quote
Old 18th December 2009, 04:30 PM   #85
diyAudio Member
 
Ultima Thule's Avatar
 
Join Date: Jan 2004
Location: Koskenkorva Land
Quote:
Originally Posted by AKSA View Post
Wahab,

I note quiescent here is 240mA, pretty deep Class AB; not sure what output, but is that around 20Vp?

Hugh,

was that a reply to sajti's post where he provided an attachment of the test setup for the ON-Semi transistors, then I just wonder how did you come to the conclusion the Iq is 240 mA?

I downloaded the datasheet but couldn't see anything speced.

I would have assumed, according to the theoretical proper biasing for "lowest" crossover distortion, it would be ~52 mA.


Wahab,

could you perhaps simulate with Iq = 52 mA, would be interesting to know the THD figures just out of curiosity, thanks.

Cheers Michael

Last edited by Ultima Thule; 18th December 2009 at 04:33 PM.
  Reply With Quote
Old 18th December 2009, 04:47 PM   #86
diyAudio Member
 
Steve Dunlap's Avatar
 
Join Date: Sep 2008
Location: Here
That information is printed on the graphs Wahab posted. It also says 100W at 8 ohm. Post 70.
  Reply With Quote
Old 18th December 2009, 04:55 PM   #87
wahab is offline wahab  Algeria
diyAudio Member
 
Join Date: Nov 2009
Location: algeria/france
the figures are higher with low quiescent current, furthermore at these
levels, close to clipping , the transfer function is heavily (literaly) distorded,
and there s no feedback to balance it...so the only mean to reduce
distorsion is to increase quiescent current, as the degeneration of
the 0.5R emitter resistance is anecdotic...

here the spectrum for 52 ma quiescent current..
Attached Files
File Type: zip MJL 21193 21194 THD.zip (5.3 KB, 85 views)
  Reply With Quote
Old 18th December 2009, 04:58 PM   #88
wahab is offline wahab  Algeria
diyAudio Member
 
Join Date: Nov 2009
Location: algeria/france
Quote:
Originally Posted by Steve Dunlap View Post
That information is printed on the graphs Wahab posted. It also says 100W at 8 ohm. Post 70.
yes, steve, but iddle currents are higher in these sims,
about 250 mA...somhow hard class AB...
  Reply With Quote
Old 18th December 2009, 05:09 PM   #89
diyAudio Member
 
Ultima Thule's Avatar
 
Join Date: Jan 2004
Location: Koskenkorva Land
Quote:
Originally Posted by Steve Dunlap View Post
That information is printed on the graphs Wahab posted. It also says 100W at 8 ohm. Post 70.
Steve,

Yes, but my post concerned post #71, or perhaps do you know what is the Iq?


Quote:
Originally Posted by Wahab
the figures are higher with low quiescent current, furthermore at these
levels, close to clipping , the transfer function is heavily (literaly) distorded,
and there s no feedback to balance it...so the only mean to reduce
distorsion is to increase quiescent current, as the degeneration of
the 0.5R emitter resistance is anecdotic...

here the spectrum for 52 ma quiescent current..
Wahab,

thanks for making the simulation, very kind of you!
Sorry for not understanding, by saying "clipping" did you mean with lower Iq it's closer to "turned off" output device or as in general understood, clipping into the rails voltage?

Cheers Michael
  Reply With Quote
Old 18th December 2009, 05:20 PM   #90
wahab is offline wahab  Algeria
diyAudio Member
 
Join Date: Nov 2009
Location: algeria/france
Quote:
Originally Posted by Ultima Thule View Post
Steve,

Wahab,

thanks for making the simulation, very kind of you!
Sorry for not understanding, by saying "clipping" did you mean with lower Iq it's closer to "turned off" output device or as in general understood, clipping into the rails voltage?

Cheers Michael
since the rail voltage is +-50V, at 100W RMS,the output is close to clipping..
the emitter 0.5R degeneration bring a 2.5 V /rail loss..
if we add the Vbe at these current, we end with no more than a
margin of 6.5 V before saturation of the conductive device is effective....
the other device has reached switch off state long before the conductive
device hit the 40V peak..
  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
Output transistor power dissipation. nigelwright7557 Solid State 11 26th May 2008 01:55 PM
Power horizontal deflection transistors work fine in output stages ? aldovan Solid State 7 31st August 2007 01:31 PM
sziklai-darlington diamond buffer (SDDB) for power output stages mtlin12 Solid State 5 1st April 2005 06:55 AM
power transistor output capacitance hienrich Solid State 3 26th December 2004 07:18 AM


New To Site? Need Help?

All times are GMT. The time now is 12:24 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