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Old 23rd December 2009, 09:05 PM   #201
syn08 is offline syn08  Canada
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Quote:
Originally Posted by wahab View Post
syn08, you miss the fact that Ft are measured with very low impedance
sources, thus rendering the influence of Cbe irrelevant for a large
part of the curve..
No. A rigurous definition of Fc is "the frequency at which the current through the imaginary and real part of the input impedance are equal".

Otherwise, I don't know where the posted curves are, therefore I can't really get into such a discussion.
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Old 23rd December 2009, 09:20 PM   #202
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BV,
Quote:
speed and removing base charges are not an issue..
They are always an issue. The beautiful measurements don`t show that either.
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Old 23rd December 2009, 09:32 PM   #203
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Originally Posted by PMA View Post
OK guys, someone would like to bring and post a measured comparison of OP stages based on 2SA1943/2SC5200, MJL1302/3281 and MJL21194/3 under heavy load conditions at some 30kHz? This might be very ineteresting, probably more than a purely theoretical debate.
Whoever does these comparisons please use the latest japanese versions and not 30 year old parts, the new parts for audio outputs by toshiba is 2sa2121 and 2sc5949. These have according to datasheet about the same SOA of the onsemi and are faster than the older parts they replace with much lower the capacitances of the onsemi.
Some comparisons with sankens like 2sa1303 and compl would also be welcome.

Bob, these are some of the more modern japanese transistors you asked about. Other outputs Ive tried is allegro sytems 2sc6011 and compl which perform very well too. From what i understand these are made in the US using sanken process technology.
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Old 23rd December 2009, 09:42 PM   #204
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Quote:
Originally Posted by Lumba Ogir View Post
BV,

They are always an issue. The beautiful measurements don`t show that either.
This is just a plain HOAX. And is just an ALIBI for avoiding any kind of EMBARASSING testing on so called "hi-end" equipment.

Piercarlo
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Old 23rd December 2009, 10:01 PM   #205
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Piercarlo,
discharging the base takes time, precious time. Its a slow-moving charge. No test needed.
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Old 23rd December 2009, 10:18 PM   #206
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Quote:
Originally Posted by PMA View Post
I am very sure that BV is very well aware of this, and can solve it on a circuit basis very effectively.

We are not in a 1st class of a primary school here.
PMA,

It may very well be the case that BV understands this. It may also be that this issue is primary school for some as smart as you.

However, I always try to post clearly and completely so that most people reading the forum can understand and learn something if they do not know it already. I always try to do this in a way that is not condescending.

Cheers,
Bob
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Old 23rd December 2009, 10:28 PM   #207
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Quote:
Originally Posted by wahab View Post
here the configuration...
if the 2R resistance is increased, Ft collapse dramatically..
each current source is adjusted so the Ic is 4 A...
Where did you get that circuit for measuring ft? It does not look like it measures ft to me. Looks like it is measuring some combination of gm and Miller effect from the Ccb capacitor. If you claim this is a legit circuit for measuring ft, please give us a reference for where you got it.

Thanks,
Bob
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Old 23rd December 2009, 10:42 PM   #208
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Quote:
Originally Posted by homemodder View Post
2sa2121 2sc5949 2sc6011
The devices you mention here should be compared to the OnSemi NJW (TO-3P) devices and not the MJL (TO-264) devices.
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Old 24th December 2009, 12:03 AM   #209
wahab is offline wahab  Algeria
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Quote:
Originally Posted by Piercarlo View Post
How can I read "emf" format? Which program open it?

Thanks
Piercarlo
double click on the item as soon as ujnzip, window automaticaly open it with its image displayer..
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Old 24th December 2009, 12:10 AM   #210
wahab is offline wahab  Algeria
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Quote:
Originally Posted by Bob Cordell View Post
Where did you get that circuit for measuring ft? It does not look like it measures ft to me. Looks like it is measuring some combination of gm and Miller effect from the Ccb capacitor. If you claim this is a legit circuit for measuring ft, please give us a reference for where you got it.

Thanks,
Bob
sorry, bob, i didn t mention the actual testbed...
the ac source is not at fixed frequency...
there a sweep in the programed frequency range, and the soft calculate
the frequency response in the boundaries you choose...


regards
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