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Old 1st November 2010, 11:05 AM   #311
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unfortunately, this smells like an "opportunity" for counterfeiters. if i were the one making the decisions, i would have a date code cutoff from one thickness to the other and leave no ambiguity for someone to exploit.
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Old 2nd November 2010, 05:39 PM   #312
Salas is online now Salas  Greece
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Default 2SC3953 Sanyo

Are those the correct cockroaches?
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File Type: jpg DSCF2461.JPG (301.1 KB, 319 views)
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Old 2nd November 2010, 07:41 PM   #313
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The more shabby Japanese devices look, the bigger chance of being genuine, imo.
So these look fine to me, identical to mine.
Couple of years ago i would have thought chances of Sanyo video TO126s being faked would be relatively small.
Used legs and the correct package details, safer bet than sparkling beauties.

(but what do I know, they shafted me with dual JFETs twice now. my machismo shell may have cracked on the surface only, but my gentle breeze inner nature still feels fragile, soiled and violated)
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Old 2nd November 2010, 08:13 PM   #314
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Thanks. Reassuring. I want them for VAS or cascoding heavy ma and high gm. What do you reckon, good choices?
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Old 2nd November 2010, 08:21 PM   #315
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Eeh, you don't think you'll have to do heavy mA in both cases ?
For lower levels there are both better and cheaper ones.
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Old 2nd November 2010, 08:30 PM   #316
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60-80mA. What better for 20-40mA?
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Old 3rd November 2010, 10:27 AM   #317
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2sc3953 is good for VAS & Pre-Driver duty.
120Vce0 is a limitation.
It has flat gain from 3mA to 90mA
It has fT~230MHz @7mA
Your Dgrade 60 to 120 hFE @50mA is a bit low but you are never going to use them at that current. Check hFE @ a more usable current for your use.
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Old 3rd November 2010, 10:31 AM   #318
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Thanks Andrew. I can use them at 40-60mA. I have loads of high Idss Jfets 10-15mA that I could group by 4 and shield in a cascode for instance. Do you think its not a good idea when hfe will degrade at about 120?
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Old 3rd November 2010, 02:20 PM   #319
AndrewT is online now AndrewT  Scotland
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I did not say degrade. I said Dgrade, The extra letter code shown in your pic.

Dgrade is 60 to 120hFE at test current of 50mA.
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Old 3rd November 2010, 03:55 PM   #320
wg_ski is offline wg_ski  United States
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Quote:
Originally Posted by Ivey View Post
In heat flow, there are many factors that one have to consider.
And one that nobody here had considered yet is R(th)C-S. Yep, case to sink.
The thinner tab will NOT be as flat and have as good a contact if mounted using the scew hole. The thicker tab will have better transfer to the sink in this case. If mounted by pressure contact over the epoxy case (where the actual die is underneath) thermal contact will be similar IF the flatness coming out of the factory is as good (it may not be since they're doing this to be cheap).

If you don't think this matters, try mounting a high power microwave transistor without the proper shims and bang you head for weeks wondering why your gain is 4 dB low.
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