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Old 26th April 2011, 10:42 PM   #31
AKSA is offline AKSA  Australia
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Lineup,

Can I ask why you need Q1? You could use two LEDs and a couple of diodes and a pot, because you don't have a critical bias issue with temperature using hexfets since the tempco is negative above about 200mA.

Otherwise, I think it's a terrific design, hats off!

Hugh
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Old 27th April 2011, 12:35 AM   #32
GregH2 is offline GregH2  Australia
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Hugh,

Are you able to post a schematic of your proposal? I would really like to model such a design...but I would like to up the bias and make it operate in class A.
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Old 28th April 2011, 05:30 AM   #33
mikelm is offline mikelm  England
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Quote:
Originally Posted by AKSA View Post

Otherwise, I think it's a terrific design, hats off!

Hugh
Of the several designs posted by lineup here to which one are you referring with the comment above ?

cheers

mike
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Old 28th April 2011, 06:48 AM   #34
lineup is offline lineup  Sweden
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Originally Posted by MiiB View Post
You could also keep the fine zetex mosfets and let them drive a pair of Laterals that has only half the input capacitance... I like this circuit concept....
True. What you say.
But as you know there is a shortage of 2SK1058/2SJ162.
I like to help people to get transistors they can more easily find.
And IRFP240/IRFP92440 are pretty much standard.
What I gather, these laterals are now more exotic components.
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Old 28th April 2011, 06:53 AM   #35
lineup is offline lineup  Sweden
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Quote:
Originally Posted by AKSA View Post
Lineup,

Can I ask why you need Q1? You could use two LEDs and a couple of diodes and a pot, because you don't have a critical bias issue with temperature using hexfets since the tempco is negative above about 200mA.

Otherwise, I think it's a terrific design, hats off!

Hugh
AKSA, thanks for posting here.
Your word is always something to respect.

Do really IRFP240/9240 have negative tempco above 200mA.
I thought it was only laterals.
If it is possible to simplify the bias circuit, I am open for this.
On the other hand, using this VBE-multiplier does not hurt.

I should say I have tried one version with bootstrap.
To make it even more simple.
It is certainly possible, but I feel better with CCS.
I am a guy hunting low THD. What we call Hifi. To the last decimal.
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Last edited by lineup; 28th April 2011 at 07:12 AM.
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Old 28th April 2011, 07:03 AM   #36
lineup is offline lineup  Sweden
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swordfishy
I would be happy if someone tried my circcuit in a real project.
Thanks for your interest.

Of course we can run it in 2A or 1.5A.
I suuggest lower supply to +/-25 Volt, with one 2x18VAC transformer.
And increase bias to 1.5A.
This will cost like 75 Watt to dissipate at heatsink.
I would say we keep Q1.
Because it is, I think, more simply.
Otherwise, if we do not use zener, there will be plenty of diodes and LED and trimpot to replace it.

I will post a Class A version with +/-25 Volt for you
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Old 28th April 2011, 07:05 AM   #37
lineup is offline lineup  Sweden
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Originally Posted by mikelm View Post
Of the several designs posted by lineup here to which one are you referring with the comment above ?
I am sure he means the last diagram.
It is also quite a bit different from previous.
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Old 28th April 2011, 07:19 AM   #38
MiiB is offline MiiB  Denmark
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Linup..

I think there's is plenty good replacements for the Laterals.. I believe that you have showed a few..rumor says that Renesas was affected by the earthquake, but have not yet seen the impact..Semlab buz 900.. versions sells through Farnell...
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Old 28th April 2011, 07:43 AM   #39
lineup is offline lineup  Sweden
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swordfishy
Here is a Class A variant.
Components in red are those that should be adjusted.
For 0 Volt at output and to adjust bias 1.5-2.0A
Attached Images
File Type: png 2sk170_irfp240_1d_classa.png (12.1 KB, 1843 views)
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Old 28th April 2011, 07:48 AM   #40
lineup is offline lineup  Sweden
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Linup..

I think there's is plenty good replacements for the Laterals.. I believe that you have showed a few..rumor says that Renesas was affected by the earthquake, but have not yet seen the impact..Semlab buz 900.. versions sells through Farnell...
I would like to get me the spice models of BUZ900 and complementary.
To use 2SK1058/2SJ162 if people will have to replace is not interesting to me.
And you say there are laterals to find.
Good if this is so.
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