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Old 2nd December 2016, 09:51 PM   #1
Nelson Pass is offline Nelson Pass  United States
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Default DEF Amp

I am going to start this thread around the circuit shown at BAF 2016,
seen at the end of the talk on the video, and attached here in simplified

I am calling it DEF, which stands for Depletion / Enhancement Follower.
It is a self-biasing push-pull output stage which has some interesting
characteristics, not the least of which is low temperature drift which allows
stable undegenerated operation.

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File Type: jpg DEF.jpg (203.4 KB, 5132 views)
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Old 2nd December 2016, 09:56 PM   #2
Zen Mod is offline Zen Mod  Serbia
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oh boy ...... here we go again

I'm outa here and outa electronics

not just that I can't keep up with Papamps .......... what's more important - I can't keep up even with just 2% of kwayzee Papawittyness

my Papa is smarter than your Nelson !
clean thread; Cook Book;PSM LS Cook Book;Baby DiyA ;Mighty ZM's Bloggg;Papatreasure;Papa... by Mighty ZM
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Old 2nd December 2016, 10:06 PM   #3
Dennis Hui is online now Dennis Hui  Canada
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Watching this with great interest. Thanks Papa!

We are fearless amplifier builders. A little heat doesn't scare us at all.
- NP 2002
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Old 2nd December 2016, 10:07 PM   #4
xrk971 is offline xrk971  United States
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Very cool. Thank you for the new toy Mr Pass.

What parts can you recommend for the interested student to try out at home? The video shows a voltage divider on the gate of the P channel to balance offset. What values go there?
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Old 2nd December 2016, 10:21 PM   #5
riksu is offline riksu  Finland
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Old 2nd December 2016, 10:25 PM   #6
Soundhappy is offline Soundhappy  France
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Papa go from
class A amplifiers with full range speakers
sings like angels in heaven
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Old 2nd December 2016, 11:03 PM   #7
needtubes is offline needtubes  United States
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Originally Posted by Nelson Pass View Post
...I am calling it DEF...

Very interesting, though it will be a challenge to find enhancement P-channels whose Vgs matches that of available depletion parts... The IXYS parts all hang around -2V for reasonable bias (<2A), so maybe the 2SJ201 could work. The USCi and Infineon JFETs all require very negative (<-7V) bias, though. Perhaps, once again, the Semisouth part is just special...
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Old 2nd December 2016, 11:36 PM   #8
dimkasta is offline dimkasta  Greece
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An externally hosted image should be here but it no longer works. Please upload images instead of linking to them to prevent this.

Thanks for all the fun
Too many projects... so little time...
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Old 2nd December 2016, 11:50 PM   #9
wdecho is offline wdecho  United States
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Some of you young whizzes fill in the blanks with some available parts and I will build. I already have some heatsinks, 20V transformer and PS section ready to build while waiting the BAF and a buildable project.
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Old 3rd December 2016, 12:48 AM   #10
rideht is offline rideht  Germany
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Great, thank you so much, i am interested in this
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