A CFB BJT preamp - any comments? - 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 21st June 2006, 07:58 AM   #1
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
Default A CFB BJT preamp - any comments?

Here it goes:
Attached Images
File Type: gif cfb.gif (9.7 KB, 1271 views)
  Reply With Quote
Old 21st June 2006, 08:04 AM   #2
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
Blog Entries: 4
First: 100 ohms input impedance? A bit low, don't you think?

Second: As amp it will work but you must consider different transistors (not 100% alike) and establish working conditions.

Your design is pretty much alike mine and it works splendidly. As pointed out earlier, the power supply must be clean due to poor PSRR.

You must have 22-47 pF at least from the Q11, Q12 collectors down to ground in order to get a nice step response.
__________________
/Per-Anders (my first name) or P-A as my friends call me
Super Regulator SSR03 Group buy. Still time for signing up.
  Reply With Quote
Old 21st June 2006, 08:06 AM   #3
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
Per,

an experienced designer like you knows that there is a high impedance input (+IN) at emmiters of Q1-Q2.
  Reply With Quote
Old 21st June 2006, 08:10 AM   #4
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
Blog Entries: 4
Since it's an inverting amp R2 is more or less the input impedance, yes Q1, Q2 is grounded, yes?
__________________
/Per-Anders (my first name) or P-A as my friends call me
Super Regulator SSR03 Group buy. Still time for signing up.
  Reply With Quote
Old 21st June 2006, 08:17 AM   #5
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
Any problem to ground R2 and have input at Q2-Q3 emitters, resulting in non-inverting amp??

The circuit is a hint, not a cookbook.
  Reply With Quote
Old 21st June 2006, 08:23 AM   #6
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
Default Non-inverting

is here:
Attached Images
File Type: gif cfb_ni.gif (9.7 KB, 1062 views)
  Reply With Quote
Old 21st June 2006, 08:27 AM   #7
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
Blog Entries: 4
That's better if you really ment "non-inverting" but what sort of comments did you want?
__________________
/Per-Anders (my first name) or P-A as my friends call me
Super Regulator SSR03 Group buy. Still time for signing up.
  Reply With Quote
Old 21st June 2006, 08:34 AM   #8
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
There is a difference in behaviour of non-inverting and inverting circuit of this kind. For gain like 10x it does not matter, for 1x the inverting behaves much better. We could increase input impedance of the inverting to some 1k and FB to 10k and still having excellent parameters. Buffer at the input would be needed. Not a case for non-inverting.

What kind of comments? This is a "PIM-free" topology
  Reply With Quote
Old 21st June 2006, 09:07 AM   #9
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
Blog Entries: 4
10k is probably too much if you want max speed out of the amp.
__________________
/Per-Anders (my first name) or P-A as my friends call me
Super Regulator SSR03 Group buy. Still time for signing up.
  Reply With Quote
Old 21st June 2006, 03:39 PM   #10
PMA is offline PMA  Europe
diyAudio Member
 
PMA's Avatar
 
Join Date: Apr 2002
Location: Prague
10k would result in >200kHz BW, not SR limited. You may stay non-inverting with 1k FB resistor and BW >>2MHz.
  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
Good supply for preamp, Comments? Algar_emi Solid State 229 26th July 2003 07:16 PM
Gainclone as a preamp & power amp - comments please. UncleJessie Chip Amps 1 13th July 2003 03:13 AM
Comments on a preamp design mpeg7 Tubes / Valves 9 17th September 2002 10:46 AM


New To Site? Need Help?

All times are GMT. The time now is 08:42 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