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Old 30th July 2005, 08:15 PM   #21
mzzj is offline mzzj  Finland
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Quote:
Originally posted by ChocoHolic
....you mean that you had issues with the storage time
of your BJTs... ?
Ok, storage time has heavy tolerances, but I would not expect
trouble with this when you use a BC327 in linear mode (not switched to saturation) at HiFi frequencies....

any scope pics or description of the effects that you had observed?
Storage time or whatever you want to call it, i am not pro at semiconductor physics. (Actually hate it, failed in semiconductor physics exams continuously)
Note that I was talking about frequencies up to 10Mhz. lower than 100khz was just fine with or without feedback.
I can supply some scope pics on next week. Base drive current was rather strange looking when monitored over 100r resistor
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Old 30th July 2005, 08:28 PM   #22
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....semiconductor physics are also not my favourite.
I prefer to apply these beasts rather than designing them.

10MHz: Good point !!
No doubt, that's tricky.
Already in the beginning regions of the Voodoo Land....
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Old 30th July 2005, 08:45 PM   #23
mzzj is offline mzzj  Finland
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Quote:
Originally posted by ChocoHolic

Already in the beginning regions of the Voodoo Land....

Sometimes I like to stick my head to the Wodoo Lands and see if I can learn any new tricks or Am I just got lost in thick smoke from overheated junctions
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Old 30th July 2005, 09:09 PM   #24
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Mzzj and ChocoHolic,

"Storage time or whatever you want to call it, i am not pro at semiconductor physics. (Actually hate it, failed in semiconductor physics exams continuously)"

"semiconductor physics are also not my favourite."

Ha. I used to teach this stuff. Loved it, and viscous fluid dynamics.



My new commercial 150W MOSFET R2R amp uses BC546/556 as drivers and reverse biassing to remove charge and speed switching!
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Old 30th July 2005, 09:11 PM   #25
forr is offline forr  France
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There was at least a commercial amplifier having an output made of dozens of medium power transistors, in TO220 package or similar with no heatsink. It was about fifteen years ago; I don't remeber the name except it was european and had no success at all.

Using a huge amount of devices for an output stage, problems can arrise because of parasitic capacitors and inductors.

~~~~~~~~ Forr

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Old 30th July 2005, 09:17 PM   #26
mzzj is offline mzzj  Finland
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Quote:
Originally posted by amplifierguru
Mzzj and ChockoHolic,


Ha. I used to teach this stuff. Loved it, and viscous fluid dynamics.


My new commercial 150W MOSFET R2R amp uses BC546/556 as drivers and reverse biassing to remove charge and speed switching!
Maybe you are not as lousy teacher as i had. I think my professor hates semiconductor physics or keeping lectures even more than me

150W R2R amp, can you reveal some more light on this? sounds intresting
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Old 30th July 2005, 09:27 PM   #27
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Hi mzzj,

I wish I could but there are at least three items of IP associated with this and the related 50W Class A schema that I must bed down before I take it on a roadshow to woo mfg/marketing suitors.

Cheers,
Greg
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Old 30th July 2005, 09:47 PM   #28
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Hi Greg,
...just wishing a succesful road show..
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Old 2nd August 2005, 09:22 PM   #29
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mzzj,

do you have any schematic?
One problem can also be the Miller capacitance at such high frequencies you are using, also depending on the source impedance.


Greg,

best luck to you and your new products!


Cheers Michael
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"If transistors are blueberries and FETs are strawberries, then tubes must be.. pears"
Michael 29th January 2010
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Old 8th April 2010, 07:45 PM   #30
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This approach seems to be very good in view to the sonic quality. Thule's integrated amp IA120 work with a bunch of paralleled TO-126 (unfortunately I haven't the schematic).
Mr. Nelson Pass does basicly the same by this project:
Beast with a Thousand JFETs

Who knows more commercial brands with a bunch of small signal transistors in the output power stage instead only one BjT power device in each half?
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