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.

A CFB BJT preamp - any comments?
A CFB BJT preamp - any comments?
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
A CFB BJT preamp - any comments?
Default A CFB BJT preamp - any comments?

Here it goes:
Attached Images
File Type: gif cfb.gif (9.7 KB, 1297 views)
  Reply With Quote
Old 21st June 2006, 08:04 AM   #2
peranders is offline peranders  Sweden
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
A CFB BJT preamp - any comments?
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
Group buy: SSR03 Super Regulator Power Supply. Sign up HERE 8 pcb's in interest so far.
  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
A CFB BJT preamp - any comments?
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
peranders is offline peranders  Sweden
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
A CFB BJT preamp - any comments?
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
Group buy: SSR03 Super Regulator Power Supply. Sign up HERE 8 pcb's in interest so far.
  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
A CFB BJT preamp - any comments?
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
A CFB BJT preamp - any comments?
Default Non-inverting

is here:
Attached Images
File Type: gif cfb_ni.gif (9.7 KB, 1086 views)
  Reply With Quote
Old 21st June 2006, 08:27 AM   #7
peranders is offline peranders  Sweden
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
A CFB BJT preamp - any comments?
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
Group buy: SSR03 Super Regulator Power Supply. Sign up HERE 8 pcb's in interest so far.
  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
A CFB BJT preamp - any comments?
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
peranders is offline peranders  Sweden
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
A CFB BJT preamp - any comments?
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
Group buy: SSR03 Super Regulator Power Supply. Sign up HERE 8 pcb's in interest so far.
  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
A CFB BJT preamp - any comments?
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


A CFB BJT preamp - any comments?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
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 02:54 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 15.79%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright ©1999-2017 diyAudio
Wiki