Does this make sense? - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

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
Reply
 
Thread Tools Search this Thread
Old 25th September 2003, 06:00 AM   #1
Illusus is offline Illusus  Canada
diyAudio Member
 
Illusus's Avatar
 
Join Date: Sep 2002
Location: Prairie Wasteland, Canada
Default Does this make sense?

I recently received my LM3875's, this is the schematic I compiled from some of the ones floating around. Will this work?
Attached Images
File Type: jpg myigclayout.jpg (23.8 KB, 307 views)
  Reply With Quote
Old 25th September 2003, 07:44 AM   #2
diyAudio Member
 
analog_sa's Avatar
 
Join Date: Aug 2002
Location: Sofia
Quote:
Will this work?
No. Instead of compiling try copying.
  Reply With Quote
Old 25th September 2003, 07:45 AM   #3
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
It should do. It is virtually the same circuit that I started with except that I used a 47K in place of the 18K.
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  Reply With Quote
Old 25th September 2003, 07:49 AM   #4
Rudy is offline Rudy  Belgium
diyAudio Member
 
Join Date: Feb 2003
Location: Belgium
ehm ... this is inverted amp technologie ( ) but the input is on the non-inverted input from the chip ..

so it's a no go
  Reply With Quote
Old 25th September 2003, 07:50 AM   #5
diyAudio Member
 
Join Date: Mar 2003
Location: Haarlem, the Netherlands
Swap the inputs, otherwise it is a power Schmitt-trigger instead of a power amplifier.
  Reply With Quote
Old 25th September 2003, 09:13 AM   #6
Electrons are yellow and more is better!
diyAudio Member
 
peranders's Avatar
 
Join Date: Apr 2002
Location: Göteborg, Sweden
Blog Entries: 4
Illusus, wether you are skilled or not check allways the datasheet and application notes. There you have all info for using the IC. If you don't understand some parts we will happily help you.
http://www.national.com/an/AN/AN-1192.pdf
http://www.national.com/ds.cgi/LM/LM3875.pdf

I know my post is rather boring but National happens to have one of the best datasheets and application notes, very much worth reading.
__________________
/Per-Anders (my first name) or P-A as my friends call me
Super Regulator SSR03 Group buy
  Reply With Quote
Old 25th September 2003, 10:16 AM   #7
Account Disabled
 
Join Date: Apr 2003
Location: US
Quote:
Originally posted by Nuuk
It should do.

it couldn't have worked, as the inputs are swapped.

it seems that you wanted an inverting topology but with different resistor values. the resistor values will work, but the topology will not.
  Reply With Quote
Old 25th September 2003, 12:01 PM   #8
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Besides swapping inverting and noninverting inputs, and setting it up for large DC offset by not compensating for bias current, you've also got a situation where disconnecting the speaker could remove the input ground reference.

Bad circuit all around. Use the app notes as P-A suggests. Those National guys are pretty smart and actually know how to use their chip.
__________________
You might be screaming "No, no, no" and all they hear is "Who wants cake?" Let me tell you something: They all do. They all want cake.- Wilford Brimley
  Reply With Quote
Old 25th September 2003, 12:29 PM   #9
Illusus is offline Illusus  Canada
diyAudio Member
 
Illusus's Avatar
 
Join Date: Sep 2002
Location: Prairie Wasteland, Canada
Oh my... inversed input is just a typo, thanks for pointing it out, I may have followed it during construction. With that reversed, do all the values look good?

I have read the national sheet, it's not that boring . I ask because I just want to make sure everything is ok, I'm very unsure of my "skill". Someone once told me there are no stupid questions, I hope he didn't say that to make me look stupid.

The reason I decided to compile a couple of suggestions before I start is because it seems that on every "look at my igc" thread the changes I included now, are suggestions.
I have been reading entry level elctronics text books and plan on taking some night classes as I become more and more interested. I am starting to understand schematics not just copy them. I still don't understand much but I do get excited when I look at a simple cuircuit and can follow it. It feels good knowing which component does what, I do have a problem with how much it does of what it's doing (values)....so bear with me guys one day I may even have some noteworthy input not just annoying questions.
  Reply With Quote
Old 25th September 2003, 12:30 PM   #10
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
Quote:
it couldn't have worked, as the inputs are swapped.
I didn't check the inputs but I think that was more of a typo than anything. Still, as you guys point out - it would not work that way round.

I do agree that for anyone starting out, it is best to stick with a proven circuit.
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  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
Does USB->I2S make sense ? percy Digital Line Level 20 24th March 2009 01:23 AM
Linear voltage regulator: how to make good use of "sense" and "ground sense"? NeoY2k Analog Line Level 7 6th September 2008 11:35 PM
TL, does this now make sense? Madmike2 Multi-Way 2 8th May 2005 02:39 PM
Does this make sense ? 00940 Solid State 7 27th March 2004 09:29 PM
does this make sense? nosegoblin Solid State 9 14th February 2004 02:19 PM


New To Site? Need Help?

All times are GMT. The time now is 03:17 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