Go Back   Home > Forums > >

Solid State Talk all about solid state amplification.

Simplicity and elegance, feedback wanted!
Simplicity and elegance, feedback wanted!
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
Old 12th January 2021, 03:41 PM   #101
BesPav is offline BesPav  Russian Federation
diyAudio Member
 
Join Date: May 2011
Location: Russia, Moscow
Quote:
Originally Posted by Hans Polak View Post
First of all, a conditionally stable amp is the last thing we want, donít we ?
Ok.
Noninverting unconditionally stable amp mostly anyway have different source resistances seen from its inputs. Now, just think, do it have equal voltage drop caused by input bias current? Do this drop equal to differential and common mode? Do this drop are equal through working signal voltage swing? Do this drop are equat through input common-mode range?


So, what amp do you want now?

Have no doubt, i'll prefer to keep amp inside known stability conditions and have +60 dB feedback handicap than use unconditionally stable miller-compensated first-order one.

Last edited by BesPav; 12th January 2021 at 03:44 PM.
  Reply With Quote
Old 12th January 2021, 05:30 PM   #102
stinius is offline stinius
diyAudio Member
 
stinius's Avatar
 
Join Date: Oct 2008
Quote:
Originally Posted by SSassen View Post
I run the amplifier in balanced mode, which really is a requirement for me.
Why?

Your AC input source, is it floating? or does it have a ground reference?
__________________
Ignorance is bliss
  Reply With Quote
Old 13th January 2021, 11:37 AM   #103
Ultima Thule is offline Ultima Thule  Europe
diyAudio Member
 
Ultima Thule's Avatar
 
Join Date: Jan 2004
Location: PKS, Finland
Default Regarding Output Stage Protection Circuit

I might be wrong and I don't have access to any simulator to check it, but here's how I see it, the protection circuit for the output FET stage doesn't work as one might think, those 2 transistors Q15, Q16, and 2 diodes D3, D4, supposed to sense the voltage fall over the source resistors at 0,1 Ohm in the occurrence of a short at the output do nothing, or, almost nothing, because as we will soon see they do "protect" but in a peculiar way.

The lower side of the Vbe multiplier circuit, which is biasing the output stage, is during positive cycle clamped to the output through lower over current protection transistors collector-base diode + lower diode + source-R (Q16 + D4 + R26).

And vice-verse during negative output voltage cycle, the higher side of the Vbe multiplier circuit is clamped to the output through the upper transistors collector-base diode + upper diode + source-R (Q15 + D3 + R24), hence these two transistors do not act on the voltage fall over output FET source resistors more than two passive diodes via their base-collector diode.

And the reason the output clips harder for positive cycle is because the N-ch FET's have lower Vgs threshold than P-ch FET's, in any case the Vgs drive is always so low due to the clamping that the output FET's becomes self limiting without any protection circuit.

To make the output protection circuit (consisting of Q15, Q16, D3 and D4) engage during a short, we would need at the very least some 0,6 Volt voltage fall for each of ALL 4 devices (Q15, Q16, D3 and D4), ie. 2,4 Volt, and 2,4V over R24 alone equals to 24 Ampere for one output device, which doesn't happen due to the clamping effect explained above, ie. the protection circuit doesn't work as expected.
Attached Images
File Type: png SaE amp OP prot.png (75.0 KB, 218 views)

Last edited by Ultima Thule; 13th January 2021 at 11:57 AM.
  Reply With Quote
Old 14th January 2021, 07:22 AM   #104
Mooly is offline Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
Simplicity and elegance, feedback wanted!


petr_2009

All your posts that are unrelated to this thread have been split off to here:

Musings on amp design... a thread split.

If you wish a different title then please report post #1 of the new thread and say what you want it to be called.

Please in future do not hijack and drag other established threads off topic as you have this one.
  Reply With Quote
Old 15th January 2021, 10:57 PM   #105
MarsBravo is offline MarsBravo  Netherlands
diyAudio Member
 
MarsBravo's Avatar
 
Join Date: Feb 2017
Location: NL
Quote:
Originally Posted by SSassen View Post
Thanks! But these simulations fall apart when I run the amplifier in balanced mode, which really is a requirement for me.
SSassen, can you draw a rough sketch block diagram of your final 'balanced mode' application? I'm busy with a balanced bridge Hiraga with an unbalanced input, hence this question.


ps:
Good split Mooly!
__________________
Y/Yo=(1-X/Xo)exp2 <> Y/Yo=(e)exp(X/Xo){Xo=kT/q}
  Reply to this post

Reply


Simplicity and elegance, feedback wanted!Hide this!Advertise here!
Thread Tools

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
Amplifier Simplicity and technology... Boscoe Solid State 2 4th June 2012 08:47 AM
simplicity vs fully active ? Designated Marksman Multi-Way 13 4th June 2011 08:27 PM
Purity and simplicity of amp design lowtherdream Tubes / Valves 63 6th August 2008 09:06 AM
Baffle simplicity yields sonic dipole benefit? rick57 Planars & Exotics 19 6th October 2006 01:25 PM
'Best' cost/simplicity/performance 10 W Single Ended Class A npr Pass Labs 2 25th September 2006 10:48 AM


New To Site? Need Help?

All times are GMT. The time now is 07:09 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.00%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2021 DragonByte Technologies Ltd.
Copyright ©1999-2021 diyAudio
Wiki