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Old 23rd August 2012, 08:29 PM   #111
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Later, you can 'prune' the circuit of any extras that are not necessary.
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Old 23rd August 2012, 08:29 PM   #112
bcarso is offline bcarso  United States
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Quote:
Originally Posted by bear View Post
In terms of buffers I like Chris Paul's buffer design... not sure where to find the schematic though... a similar on was suggested in a diy thread a year or two ago and I piped in with the requisite moving of the input devices to bootstrap them to the outputs... maybe I can find that if I search enough...

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I think the only things I've seen of Chris's are hollow state, so that would be interesting.
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Old 23rd August 2012, 08:39 PM   #113
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Originally Posted by john curl View Post
You should quit 'counting' and start designing. These arbitrary rules are self limiting.
Yeah, um, I'm not that talented. Thanks for the encouragement anyway.
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Old 23rd August 2012, 08:40 PM   #114
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I think this may illustrate somewhat:

Anyone built this power Diamond Buffer amp ?

and here:

Diamante -a discrete medium power opamp

May or may not have application here.
I shoot from the hip, usually loaded with blanks or duds...

_-_-bear

I am led to believe that this is Chris Paul's work, and was perhaps published in a mid 80s (?) audio amateur if not elsewhere. I do not have the original source. But have used this exact circuit altered with jfet inpoot and mosfet outpoot... (I did use a servo, iirc to keep the DC offset nil, but that is the easy way out...)
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Last edited by bear; 23rd August 2012 at 08:43 PM.
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Old 23rd August 2012, 08:44 PM   #115
bcarso is offline bcarso  United States
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Quote:
Originally Posted by bear View Post
I think this may illustrate somewhat:

Anyone built this power Diamond Buffer amp ?

and here:

Diamante -a discrete medium power opamp

May or may not have application here.
I shoot from the hip, usually loaded with blanks or duds...

_-_-bear

I am led to believe that this is Chris Paul's work, and was perhaps published in a mid 80s (?) audio amateur if not elsewhere. I do not have the original source. But have used this exact circuit altered with jfet inpoot and mosfet outpoot... (I did use a servo, iirc to keep the DC offset nil, but that is the easy way out...)
I can ask Chris about it.
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Old 23rd August 2012, 08:47 PM   #116
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Quote:
Originally Posted by bcarso View Post
It might survive a momentary short, like a brush with a clumsy test lead ground, but it's not likely bulletproof for magic smoke releasing probers
All depends on appetites.

Yo can reasonably limit this current, without worry to loose too much on speed of rechargings.

I still can't find schematic of my buffer. It relies on the current in the tail that increases with signal voltage level, so protection works as protection from lower than threshold load resistance that is more relevant for protecting of output transistors from excess power dissipation than protecting from current on any level of signal, from zero to the rail. It gradually shifts from voltage follower to voltage to current converter. I discarded it in late 70'Th as an output stage for IC because selection/adjustment were needed, but for custom design using discrete components it is fine.
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Old 23rd August 2012, 09:09 PM   #117
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Originally Posted by EUVL View Post
Agreed.
Nice to have, not must have (less than 8 active devices).

The same applies to extendability to a fully balanced configuration, a la OPA1632.




Patrick
How many transistors is allowed?
IMHO it's not possible to design a low THD circuit with only 8 transistors, for the fun of it I designed one today, JFET ips, BJT "VAS", MOSFET "buffer" THD is in the "Guru" range.

BTW: I have dersigned a discrete differential balanced "opamp", but used more than 8 transistors, it's an all BJT design, so I guess that rules me out of the "competition" and the THD is also far too low for some.

Apart from that I guess it's not easy for you to start a GB thread with a "stinius" design.
"The worlds best discrete opamp, designed by "SW" approved by "JC" applauded by a lot of "engineers" and GEB's" Is in fact a much better sales argument.

Maybe someone could make a spec? It's not possible to design anything without a detailed spec.

Cheers
Stein
Attached Files
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Old 23rd August 2012, 09:11 PM   #118
benb is offline benb  United States
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I presume performance would be optimized by matching the beta of the LTP and complementary transistors in these circuits? Most of these signal-level transistors are pretty cheap, and one can buy lots of them for matching. Might even want to connect complementary pairs' cases together physically to give better tracking with temperature - a consideration when making a layout.
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Old 23rd August 2012, 09:38 PM   #119
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Quote:
Originally Posted by benb View Post
I presume performance would be optimized by matching the beta of the LTP and complementary transistors in these circuits? Most of these signal-level transistors are pretty cheap, and one can buy lots of them for matching. Might even want to connect complementary pairs' cases together physically to give better tracking with temperature - a consideration when making a layout.
Yeah, that's usually the case.
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Old 23rd August 2012, 10:13 PM   #120
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Quote:
Originally Posted by bear View Post
I think this may illustrate somewhat:

Anyone built this power Diamond Buffer amp ?

and here:

Diamante -a discrete medium power opamp

May or may not have application here.
I shoot from the hip, usually loaded with blanks or duds...

_-_-bear

I am led to believe that this is Chris Paul's work, and was perhaps published in a mid 80s (?) audio amateur if not elsewhere. I do not have the original source. But have used this exact circuit altered with jfet inpoot and mosfet outpoot... (I did use a servo, iirc to keep the DC offset nil, but that is the easy way out...)
I have some power amp designs that use a modified diamond buffer output. Bob Cordell mentions them in his book.
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