MY LM4780 Amp - 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 19th January 2007, 09:38 AM   #1
ziling is offline ziling  China
diyAudio Member
 
Join Date: Feb 2006
Location: GUILIN
Send a message via ICQ to ziling
Default MY LM4780 Amp

MY LM4780 to 3 link Amp
Attached Files
File Type: pdf lm318lm4780x3.pdf (37.8 KB, 429 views)
  Reply With Quote
Old 19th January 2007, 09:11 PM   #2
traw is offline traw  United States
diyAudio Member
 
Join Date: Sep 2005
hmmm.... have something similar before in regards to an opamp up front driving them with an outer feedback loop. Not myref but a commercial 'bpa300' implementation. Except inner feedback was 56/1+1 and outter feedback 56/1+1.... It was a great sounding amp.

What is the philosphy of the opamp feedback wrapping the inner paralleled chips?

What does the cap + resistor across the inputs do? (my ignorance). On other i've seen was 470pf solely...

Paralleled 6 ? why not bridge to creat larger voltage swing?
  Reply With Quote
Old 20th January 2007, 04:03 PM   #3
gootee is offline gootee  United States
diyAudio Member
 
Join Date: Nov 2006
Location: Indiana
Blog Entries: 1
Default Re: MY LM4780 Amp

Quote:
Originally posted by ziling
MY LM4780 to 3 link Amp
Why do you have ~equal feedback to both + and - input pins of each chipamp? Is it some type of Howland current source topology?

- Tom Gootee

http://www.fullnet.com/~tomg/index.html

-
  Reply With Quote
Old 20th January 2007, 04:17 PM   #4
gootee is offline gootee  United States
diyAudio Member
 
Join Date: Nov 2006
Location: Indiana
Blog Entries: 1
Quote:
Originally posted by traw


What is the philosphy of the opamp feedback wrapping the inner paralleled chips?


Off the top of my head, there are a couple of standard reasons for putting a larger amp inside the forward part of the feedback loop of an opamp.

One reason is to use the larger amp as a current/power booster for the opamp, often implemented with the gain of the larger amp = 1, so it's a buffer, but with much higher power output capability. If the larger amp is configured as a Howland-type current source, the whole thing can become a voltage-controlled current source, with relatively higher current output capability. (I haven't analyzed the OP's schematic fully-enough to know if that is what he did, here.)

I have several power amplifier designs that put a chipamp into the forward part of the feedback loop of an opamp, solely to improve the performance of the chipamp. It can easily result in the improvement of the THD@20kHz by a factor of 15 or so, while also dramatically improving the transient response characteristics.

- Tom Gootee

http://www.fullnet.com/~tomg/index.html

-
  Reply With Quote
Old 6th July 2007, 04:20 AM   #5
ziling is offline ziling  China
diyAudio Member
 
Join Date: Feb 2006
Location: GUILIN
Send a message via ICQ to ziling
Click the image to open in full size.
Click the image to open in full size.
  Reply With Quote
Old 6th July 2007, 07:57 AM   #6
Tolu is offline Tolu  Germany
diyAudio Member
 
Tolu's Avatar
 
Join Date: Mar 2007
@ziling:
How does it sound? In comparison to the well known candidates (3875, 3886, ...)!

Regards

Thomas
  Reply With Quote
Old 6th July 2007, 08:11 AM   #7
ziling is offline ziling  China
diyAudio Member
 
Join Date: Feb 2006
Location: GUILIN
Send a message via ICQ to ziling
Gootee,thanks you for your explanation
  Reply With Quote
Old 6th July 2007, 06:46 PM   #8
gootee is offline gootee  United States
diyAudio Member
 
Join Date: Nov 2006
Location: Indiana
Blog Entries: 1
Quote:
Originally posted by ziling
Gootee,thanks you for your explanation
You're welcome. But please note that I'm not really an expert at these things, after many years of not working in the EE field. I have been playing around with chipamps, lately, though.

I also wanted to mention that by using several chipamps in parallel, inside of an opamp's feedback loop, there are ways to make a power amplifier that is amazingly good at driving very large capacitive loads, with truly-excellent transient-response characteristics, while still retaining extremely-low THD-20kHz.

- Tom Gootee

http://www.fullnet.com/~tomg/index.html
  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
sonic differences between inverting/non-inverting LM4780 VS both non-inverting LM4780 jarthel Chip Amps 5 19th July 2007 01:37 PM
LM4780 from who? jarre Chip Amps 6 10th August 2006 08:04 AM
lm4780 p/s j9184p Power Supplies 4 28th June 2006 05:18 PM
anybody tried a LM4780? travis Chip Amps 162 23rd March 2005 09:14 PM
lm4780 odysseybmx414 Chip Amps 2 22nd February 2005 07:13 AM


New To Site? Need Help?

All times are GMT. The time now is 01:58 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