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Old 4th February 2011, 02:06 PM   #1
ontoaba is offline ontoaba  Indonesia
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Default An Exotic ClassA Amplifier (never seen before).

I got this picture while trying to get very high efficiency classA.
Just sharing some fun.
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File Type: png Another ClassA.PNG (4.7 KB, 765 views)
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Old 4th February 2011, 03:03 PM   #2
jcx is offline jcx  United States
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"non-switching" Class AB has been around for a while now - along with those who want to claim they've invented it and to "brand" it as "Class A"

I think most designers would really expect "Class A" to mean that each of the output devices contribute nearly linearly to output over the full cycle

the mere fact that you've not turned off a output Q doesn't change the fact that you get a nonlinear output gm slope change - the more localized, "sharper" you change the current slope in the output devices the higher order the introduced nonlinearity

New Class A, Super-A, Non-Switching : need a revival ?

you should be able to pull up ~100 threads with searches of Tanaka, Pass (non)switching, sliding bias

Last edited by jcx; 4th February 2011 at 03:19 PM.
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Old 4th February 2011, 06:58 PM   #3
Bigun is offline Bigun  Canada
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Quote:
Originally Posted by ontoaba View Post
Just sharing some fun.
Looks amazing, I think this needs a new name, maybe call it Class B ?
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Old 4th February 2011, 10:36 PM   #4
ontoaba is offline ontoaba  Indonesia
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Umm.. but it is fixed biased, at around 5A not a variable biased amplifier, and it still draw 5A when idle. This amount of current is double of normal push pull classA that only need 2.5A bias for equal output power.
No one using this one because it need twice idle current compared to normal classA. They love their power and save them.
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Old 5th February 2011, 02:04 AM   #5
Bigun is offline Bigun  Canada
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yes, but regular Class B doesn't provide enough heat, it's almost useless at this time of the year in Canada. Your new low efficiency Class B with super high idle current helps a lot and reduces cross over distortion too. I think you have a winner on your hands.
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Old 5th February 2011, 02:41 AM   #6
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I think you have a winner on your hands.
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Old 5th February 2011, 06:25 AM   #7
ontoaba is offline ontoaba  Indonesia
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The first picture, 5A dissipated only from 1.5V
With conventional classA it need 3V supply and 8A idle current for best result, I am not in canada, so I reduce the power wasted as low as possible, up to 0.5V supply used.
When supply less than 2V classB-like classA has better linearity than normal classA. I am still investigate it

I attached the result of common classA in 1.5V and 3V with 8A bias.
See US pat#4115739 for detail.
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File Type: png Common ClassA.PNG (4.7 KB, 493 views)
File Type: png pat#4115739.PNG (28.7 KB, 486 views)
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Old 5th February 2011, 07:53 AM   #8
ontoaba is offline ontoaba  Indonesia
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Another result.
OOps... class AB is the worst, that is why they using error corrections.
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File Type: png SE classA and AB.PNG (9.9 KB, 446 views)
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Old 10th February 2011, 09:59 AM   #9
ontoaba is offline ontoaba  Indonesia
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This series amlpifier is very old and ever produced as classA+, and I see that nowadays classA is still HOT like what it should be. May be something wrong with this series connection or something else. I am interesting to try one with little differences, classB input is now from output of classA. With this quick tracker:
FAST and SIMPLE driver for HEXFETS (linear use).

Reference:

1.AES Preprint no. 1382 (N-5) "High Efficiency Class A Audio Power Amplifier"
AES E-Library: High Efficiency Class A Audio Power Amplifier (Class A+ Amplifier)
2."POWER AMPLIFIER" US 4,115,739
Power amplifier - Patent 4115739
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