Feedback resistor when using bridge mode - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Chip Amps Amplifiers based on integrated circuits

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
Thread Tools Search this Thread
Old 17th May 2006, 04:53 AM   #1
diyAudio Member
Join Date: Dec 2005
Location: Sao Paulo
Send a message via MSN to -_nando-_ Send a message via Skype™ to -_nando-_
Question Feedback resistor when using bridge mode

Hi everyone !

I read all the BPA200 datasheet, because I'm building it, and of course I know the manufacturer of the chip is right, BUT I DON'T understand why the feedback resistor (in red) is placed there !

The amp is used in inverse mode, so input signal enters in the inverse input, to have a inverse output to be connected to the -V of the speaker, and wow, you have the bridge!

The normal implementation (non inverted) use the feedback resistor to compensate the signal in, with the inverted signal, so, more feedback in the inverted input, less loud the sound will be...

So, WHY the inverted implementation don't use the feedback resistor connected to the non-inverted signal in? It don't make any sense to me...

Anybody ?!

Thanks !!
Attached Images
File Type: jpg fedibecki.jpg (31.8 KB, 123 views)
  Reply With Quote
Old 17th May 2006, 05:29 AM   #2
rpapps is offline rpapps  Antarctica
diyAudio Member
Join Date: Jul 2004
Location: nowhere of interest
The purpose of Rf & Ri in all four stages is to set the gain in accordance with the formula:
Vout/Vin = 1 + Rf/Ri
In this case, voltage gain is 22 or approximately 27 dB.
(Besides, if you connected the feedback to the non-inverting input you would have positive feedback, not negative. Oscillator anyone?)
  Reply With Quote
Old 17th May 2006, 05:59 AM   #3
diyAudio Member
Greg Erskine's Avatar
Join Date: Jan 2002
Location: Sydney/Australia

Sorry, I didn't read the post carefully and posted an inappropriate answer.
Greg Erskine
  Reply With Quote
Old 17th May 2006, 06:22 AM   #4
rpapps is offline rpapps  Antarctica
diyAudio Member
Join Date: Jul 2004
Location: nowhere of interest
Hi Greg, no need to apologise.
You were absolutely correct in what you said. I just used one formula to keep things simple. However, in practical terms, it makes less than a 1/2 dB difference which can be safely overlooked.
  Reply With Quote


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
Loudspeakers in Bridge Mode losaavedra Multi-Way 1 15th June 2009 09:36 AM
Difference between Bridge & Parallel mode john_lenfr Chip Amps 13 4th July 2005 01:27 PM
How to use STK459 in bridge mode tridibesh Solid State 0 4th June 2005 07:40 AM
Inverted gainclone with noninverted bridge mode akunec Chip Amps 0 20th October 2004 12:30 AM
bridge mode for LM 3875 partyjups Solid State 2 5th June 2001 05:49 PM

New To Site? Need Help?

All times are GMT. The time now is 04:19 PM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2