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Old 6th June 2011, 11:19 AM   #31
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Join Date: Feb 2008
Location: Jackson,michigan
One thing I would like to piont out Is that even though these circuits employ opamps is that they are still operating in class a mode.
Because when the opamp is powerd with a high enough voltage it is drivng the fets entirely in its linear range and never hits the crossover point.
If it does it would be at extermly high peaks and at the risk of destruction of the fets.
Now my transistor driven design would be considered pure class a though.

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Old 6th June 2011, 11:39 AM   #32
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Join Date: Feb 2008
Location: Jackson,michigan
I started designing these type of circuits around 1995 and the stacked version in 2003 but I did not actualy build one until 2007.

I have also used them in a BTL configuration and used a little pizeo driver as a load and I was amazed in how clean and loud it was just hanging off of the breadboard.
I thought the thing was going to shatter.

I first tried sine waves ofcourse and then used some music.

I was using a resistor load and they weren't a high enough wattage and burned up quite a few to the point that I didn't have enough parts to continue.

It wasn't until a couple of months ago I figured out how to employ a high ampreage CCS to replace the load resistor.
So,I have yet to build that vesion as it is one of the many projects that I have going all at once!

the cool thing was I tried every different type of fets that I had rangeing from IRFZXX, IRF510,IRF640,IRF740 and IRF840 and they all worked.


Last edited by geraldfryjr; 6th June 2011 at 11:50 AM.
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Old 6th June 2011, 01:00 PM   #33
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Join Date: Mar 2007
Location: Canandaigua, NY USA
Ha! Gottcha all beat in the old fart department. I just found my original drawing. It's basically the same as I posted, but with different gain. It's dated 1985, so that was 26 years ago!

Jer, thanks for those circuits- interesting thoughts for some projects I'm looking at right now.
I may be barking up the wrong tree, but at least I'm barking!
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Old 6th June 2011, 01:39 PM   #34
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Join Date: Feb 2008
Location: Jackson,michigan
Very good,Conrad, I too have my original files on a floppy disk!
Anybody remember those?he,he

Glad you enjoy them and I hope they can be of use to you as I have many more versions and different styles of configurations.

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