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Old 30th April 2005, 02:58 PM   #101
MikeB is offline MikeB  Germany
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Oh, designing the gate-driverstage is the most complicated thing with ClassD...
I think, it's very important to have the correct choice of devices,
these transistors must be able to deliver up to 1 ampere for a short
time, so hfe-curve should not drop to low above ~500ma.
I am not familiar with the 2SC8050...
Cascading more EFs does not really help if the last stage is not able
to deliver the current needed.

Mike
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Old 1st May 2005, 05:43 AM   #102
Kenshin is offline Kenshin  China
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2SC8050: 1.5A(max DC current),100MHz
Quote:
Originally posted by MikeB
Oh, designing the gate-driverstage is the most complicated thing with ClassD...
I think, it's very important to have the correct choice of devices,
these transistors must be able to deliver up to 1 ampere for a short
time, so hfe-curve should not drop to low above ~500ma.
I am not familiar with the 2SC8050...
Cascading more EFs does not really help if the last stage is not able
to deliver the current needed.

Mike
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Old 1st May 2005, 10:02 AM   #103
Kenshin is offline Kenshin  China
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Yesterday I resonanced a output filter at 30KHz and got 150V peak output.

I wonder if the swords of JEDI warrior in <<Star Wars>> is done this way.
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Originally posted by MikeB
Hi Chris !

This circuit starts frightening me ! I am waiting for this amp to open
a tear in the timespace-continuom...

Mike
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Old 1st May 2005, 12:49 PM   #104
MikeB is offline MikeB  Germany
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Ouch ! And did the blue flashes cut something apart ?
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Old 2nd May 2005, 01:02 PM   #105
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JohnW: Your work looks really nice!!!!

The 2.2$ was that including the 2 regenerator coils, and bypassing caps? Because in our ZAPpulse we use quite a bit more than 2$ alone for the bypassing caps.

Will the amp get overheated if loaded with 4 Ohms (200W) and will it shut down, or just blow up?

Again i think it's beautiful work! Really compact!

Best regards

Lars
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Old 3rd May 2005, 02:44 PM   #106
Kenshin is offline Kenshin  China
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Is 5401 fast & powerful enough for gate drive? I have some dirty simulation waveforms.
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Old 3rd May 2005, 05:16 PM   #107
MikeB is offline MikeB  Germany
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Fast enough, yes ! Powerful enough ? No !
It does nearly the job, the 2n5401 works fine, but the 2n5551
enters some strange breakdown visible with scope.
I wanted to try 2n2222a or bc327, i already bought them, but
had no time yet for this project.

Mike
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Old 7th May 2005, 02:11 PM   #108
Kenshin is offline Kenshin  China
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NPN 2N5551 weaker than PNP 2N5401 ?!
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Old 7th May 2005, 06:17 PM   #109
MikeB is offline MikeB  Germany
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I don't know, the 2n5401 didn't show these symptoms, even with
more gatecharge to drive... I don't understand !

Mike
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Old 7th May 2005, 09:13 PM   #110
bcarso is offline bcarso  United States
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Sorry to come late to this thread.

I'm looking at the first post schematic, but from skimming through the extensive developments since it appears that there has been no explicit schematic revision to reflect all of the changes---or did I miss something? If not, maybe it's time for a new one (hint hint)?

The one thing that astonished me so far is the scope photo of the gentleman's 2nS risetime P-channel output, showing essentially no ringing! I haven't seen a waveform that clean since I designed some clock drivers for a spectrometer using a self-scanned photodiode array back in ~1978. As it was still the dawn of good power MOSFETs I used RF bipolars in quite an elaborate config., finally steering currents in and out of 100 ohm R's with fast diodes.

I don't know whether (again) I may have missed it, but in my experience it is vital to use a probe with a ground ref springy thing adjacent to the tip, or even better a superfast differential probe like the old Tek product. Otherwise you are looking mostly at the ringing in the scope ground lead.

Anyway, good stuff. As a newbie I am enjoying the forum.
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