can you make LM3876 work in Class A ?

[Jonnravn]

I am about to embark on a Large LM3876 adventure with 8 Lm's for each channel......
It accured to me that you can make traditional opamps work in class A by connecting the output of the opamp to the supply via a resister.....so why should that not work with power opamps (like the LM38XX series) as well?
Has anybody tried this, or is there a reson why this can not be done?

[seventenths]

You might find this interesting... I sure do

http://www.passdiy.com/pdf/diyopamp.pdf


7/10

[analog_sa]

Originally posted by Jonnravn
Has anybody tried this, or is there a reson why this can not be done?

This has been discussed more than once. Did you really search?

[Jonnravn]

Yes I have tried searching...but for som reason (no matter what i search for) I always get no results returned.... and i really don't want to read through all the chipamps posts.

[BWRX]

Try using Google and do a general search of the web. Google often returns results from threads on this forum.

[Jonnravn]

I actually got the search engine on the page to work (I just read what it said insted of just trying to do it my way....ups!
This only produced one thread I could use (there might be something about class A lm's on page 43 or 218 or 9 of some threads which does not indicate so in there headline, but my life is just to short to sit and read all of the threads involving chipamps).
I will try the google search to see if it will do better (thanx for the tip).

[Zen Mod]

http://members.lycos.co.uk/fiultra/KISS%20190.htm


try there



uh , almost forgot to ask:

"did ya search?"

[djk]

"It accured to me that you can make traditional opamps work in class A by connecting the output of the opamp to the supply via a resister....."

That will work, but it generally works better (even with small signal opamps) to use an active current source instead of the resistors.

I would use an Aleph type CCS (see Pass board).

In theory you could hit 25% efficiency, so you will need a heatsink that will dissipate 200W to put out 50W/8R, and the Aleph CCS will allow for impedance dips below 8R.

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On second thought I would just build a Pass A40 or an Aleph. AudioXpress still sells the board for the A40 for about $6. The theoretical efficiency for the A40 is 50%.

[Zen Mod]

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[Zen Mod]

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