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Old 7th December 2010, 04:38 PM   #31
Bigun is offline Bigun  Canada
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Sorry, I couldn't resist
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Old 7th December 2010, 05:18 PM   #32
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What you mean ?
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Old 8th December 2010, 01:27 AM   #33
Bigun is offline Bigun  Canada
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Quote:
Originally Posted by audiodesign View Post
What you mean ?
I was joking about the output being connected to the power supply on the linked schematic - of course for Circlotron the power supply is floating so this is just fine !

I like this new design, I think hybrids is an interesting area to explore - I'm hoping to make something myself this winter - most likely based on diamond buffer - not a new approach but a good starting point.
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Old 24th December 2010, 10:50 AM   #34
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Default N-ch output circuit designs

Linear OTL N-ch only output circuits can be made to work very well if not better than complementary output, without a lot of complexity once the underlying issues are clarified. There is no need for servo bias, the servo bias circuitry as presented in designs like Rohr's autobias (Siliconix App Note) and Auto Bias is a band aid for excessive dc operating drift issues in those discrete circuit designs. Ie the monolithic op amp(s) in these autobias approaches are basically a patch, a solution to a problem that derives from the circuit designer not doing an adequate job of meeting dc stability requirements in one or more of the discrete gain/driver stages. The basic circuit shown in Pat 5631608 (US Patent 5631608 - Driver for N-channel VFET output stage of power amplifier) with only 7 transistors (practical implementation) nicely removed all operating point drift in the driver (without autobias) and at the same time introduced the correct thermal compensation coefficient (~ -4.4 mV/C) at the gate to source of each output fet. The circuit was originally intended as an upgrade/design-around for a complementary output circuit (US Patent 4483016 - Page 1 Image - Audio amplifier) that was used under license in existing product. The new circuit not only sidestepped licensing royalties but also ended up reducing the BOM cost and performing better than its forerunner in terms of thermal stability, THD, and efficiency. Theres probably over 50,000 automotive amplifier units (Hafler MA-4, Rockford P45 & MTX TA 240 TA280 TA2300 TA4160 TA4320 and later models) out there in the field with a variant of that configuration. The bias tracked perfectly from -40 C to 100 C which is basically the peak ambient temp possible within the product enclosure (Alaska to Arizona trunk temp) etc. This circuit in conjunction with 2 TO-220's N-ch (IRF-540 etc) fets achieved 100 W @ 4 ohms with .035 % THD @ 20 khz - with no more than 50 mA of bias, the mid band distortion @ 1khz was .005 THD.
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Old 27th December 2010, 06:25 AM   #35
ontoaba is offline ontoaba  Indonesia
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Quote:
Originally Posted by Bigun View Post
I was joking about the output being connected to the power supply on the linked schematic - of course for Circlotron the power supply is floating so this is just fine !

I like this new design, I think hybrids is an interesting area to explore - I'm hoping to make something myself this winter - most likely based on diamond buffer - not a new approach but a good starting point.
Another floating supply:
Its only need +50V for +/-45V outputs.


Another one.
No schematic (its prevented to be published) , but I just post them long ago. All N-channel, tracking rails, and good crossing management.
QUASI is not that bad, really, (I post some proof here).

Last edited by ontoaba; 27th December 2010 at 06:35 AM.
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Old 10th March 2011, 07:46 AM   #36
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Default can anyone .

can anyone try to sim this scheme of quasi mosfet.

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Old 10th March 2011, 07:49 AM   #37
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<a href="http://s1096.photobucket.com/albums/g324/jon2xflash/?action=view&amp;current=mosfetv2.jpg" target="_blank"><img src="http://i1096.photobucket.com/albums/g324/jon2xflash/mosfetv2.jpg" border="0" alt="Photobucket"></a>

<a href="http://s1096.photobucket.com/albums/g324/jon2xflash/?action=view&amp;current=mosfetv1kit.jpg" target="_blank"><img src="http://i1096.photobucket.com/albums/g324/jon2xflash/mosfetv1kit.jpg" border="0" alt="Photobucket"></a>
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Old 1st May 2011, 10:09 AM   #38
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where are to find the schematics now from this old, follow website ??
http://web.archive.org/2003010100000...mplifiers.com/
I don't find the appropriate download aera about the currently version
High End Audio MOSFET Amplifiers
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Old 5th May 2011, 05:39 PM   #39
knutn is offline knutn  Norway
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Quote:
Originally Posted by amplifiers inc View Post
The basic circuit shown in Pat 5631608 (US Patent 5631608 - Driver for N-channel VFET output stage of power amplifier) with only 7 transistors (practical implementation) nicely removed all operating point drift in the driver (without autobias) and at the same time introduced the correct thermal compensation coefficient (~ -4.4 mV/C) at the gate to source of each output fet.
I have looked at the patent, and I don't see how you can control the output bias without controlling the tail current (of the input differential pair).
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Old 5th May 2011, 07:12 PM   #40
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Quote:
Originally Posted by knutn View Post
I have looked at the patent, and I don't see how you can control the output bias without controlling the tail current (of the input differential pair).
check out the circuit by post #23 about
Siliconix & Siemens NMOS amplifiers
check out also third URL about 1) by post #1 on this thread and follow:
Kaneta method's all FET power amplifier
In all cases bias control is with help of thermal resistors.
If you want such a topology with bias servo, buy the book
Audio Amateur "Power Amp Projects" - go to
audio amateur - power amp projects
or the magazine 2/1988 about
Audio Amateur Magazine Back Issue #2 1988 - Dayton
and read this articles:
A 40W All-MOSFET Power Amp (Part I) 2/1988
A 40W All-MOSFET Power Amp (Part II) 3/1988
(Chater's 40W Servo Controlled MOSFET Amp)
Check also this thread:
William T Chater power amp
and here the patent paper from this author:
http://www.freepatentsonline.com/5055797.pdf
Which commercial brands uses that topology?
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Last edited by tiefbassuebertr; 5th May 2011 at 07:41 PM.
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