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Article: Beast With a Thousand Jfets
Article: Beast With a Thousand Jfets
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Old 23rd January 2013, 12:44 AM   #71
Loudthud is offline Loudthud  United States
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The parallel combination of 100 opamps with 560 ohms in series with the output would give an output impedance of 5.6 ohms. The opamps have short circuit protection, they don't need that big of a resistor. The input offset is low enough that something like 10 ohms would work fine.
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Old 23rd January 2013, 01:18 AM   #72
Loudthud is offline Loudthud  United States
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At an output of 20mA each opamp the output voltage can swing to about 2V from the rail. With 18V rails you have 16V peak, 2 A peak (20mA per) , that's 16W rms with 8 ohm load. Distortion raises quite a bit if you want too much gain or too much output current, especially at higher frequencies. Keep the output buffers at a gain of 1 or slightly higher. There is probably a better part out there.

I didn't try to figure out which package is best, probably the dual in 8 pin DIP.

Data sheet: http://www.ti.com/lit/ds/symlink/opa134.pdf
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Old 23rd January 2013, 06:38 AM   #73
R-K Rønningstad is offline R-K Rønningstad  Norway
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Quote:
Originally Posted by Zen Mod View Post
isn't place for damn 8-legged bugs in some other thread ?

Then we are at least two who believes so!
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Old 23rd January 2013, 06:48 AM   #74
portreathbeach is offline portreathbeach  United Kingdom
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OK. I have now posted my question and schematic here:

http://www.diyaudio.com/forums/chip-...ml#post3338443




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Old 23rd January 2013, 05:27 PM   #75
Dzius is offline Dzius  Poland
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Quote:
Originally Posted by Zen Mod View Post
isn't place for damn 8-legged bugs in some other thread ?
It takes debuger !!!
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Old 23rd January 2013, 07:19 PM   #76
Nelson Pass is offline Nelson Pass  United States
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Article: Beast With a Thousand Jfets
Quote:
Originally Posted by portreathbeach View Post
OK. I have now posted my question and schematic here:
http://www.diyaudio.com/forums/chip-...ml#post3338443
Maybe you want to see what Douglas Self has done with this.

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Old 23rd January 2013, 07:27 PM   #77
portreathbeach is offline portreathbeach  United Kingdom
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Cheers Nelson. I've just downloaded the PDF of the design, very interesting read. Will have to make a similar thing
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Old 30th January 2013, 10:13 PM   #78
Antoinel is offline Antoinel  United States
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Article: Beast With a Thousand Jfets
Default Maybe Large Scale Integrate [LSI] this Beast

Quote:
Originally Posted by Nelson Pass View Post
Maybe you want to see what Douglas Self has done with this.

This Beast may lend itself to LSI on a Si and/or a SiC wafer. Afterall, each individual P and N channel FETs belonged to a field of hundreds or thousands simultaneously made on a wafer by TOSHIBA or other. There is a precedence with CMOS Hex Inverters. Ditto for OP Amps which are also made by the tens or hundreds on a single wafer. Just link'em up.
The meticulously hand-wired prototype Beast worked with impeccable performance. The ongoing interest by DIYers worldwide may drive demand for the handmade and LSI Beast versions. The LSI Beast may have a lower cost than hand made.

Best regards.
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Old 30th January 2013, 11:20 PM   #79
Blues is offline Blues  United States
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Like I speculated before, I think Mr. Pass put together these little monsters to characterize it as a whole and reference it for his Pass SITs production...
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Old 30th January 2013, 11:42 PM   #80
Antoinel is offline Antoinel  United States
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Article: Beast With a Thousand Jfets
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Originally Posted by Blues View Post
Like I speculated before, I think Mr. Pass put together these little monsters to characterize it as a whole and reference it for his Pass SITs production...
Blues: Please direct me to the post of your speculation.
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