Author: ArameFarpadoDate: 04:35 19-04-08
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Hi all...
a transistor "BD435" is giving me 440 in hFE test on the multimeter, when
the tecnical data i've found tell me min=40 max=475...
does this mean the transistor is really in good shape?
can it be busted and still give a good hFE test result on the multimeter?
thanks
ArameFarpado
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Author: Nigel HeatherDate: 06:06 19-04-08
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Not necessarily. The hFE will vary for each transistor depending on IC
(Collector Current). So for the same transistor the hFE will vary depending
on what collector current you drive through it. So the range of hFE they
give is probably not so much an indictation of manufacturing tolerance (this
transistor is better than that one) but more an indication that ant
transistor will vary depending on how you drive it.
Of course there are manufacturing tolerances aswell so the range is a
combination of the two.
The tester probably uses a low IC which will lead to a high hFE. If in your
application you drive IC to say 1A you would probably find the hFE for your
transistor would drop down low.
Cheers,
Nigel
"ArameFarpado" <a-farpado.spam@netcabo.pt> wrote in message
news:fucasb$cru$1@news.datemas.de...
> Hi all...
>
> a transistor "BD435" is giving me 440 in hFE test on the multimeter, when
> the tecnical data i've found tell me min=40 max=475...
>
> does this mean the transistor is really in good shape?
> can it be busted and still give a good hFE test result on the multimeter?
>
> thanks
> ArameFarpado
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Author: ArameFarpadoDate: 09:24 19-04-08
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Thanks.
i've just made a strange descovery:
if i leave the base pin not connected, the hFE result is the same.
so i guess this hFE test is not for checking if the transistor is fine or
busted.
thanks again
ArameFarpado
Em Sábado, 19 de Abril de 2008 11:06, Nigel Heather escreveu:
> Not necessarily. The hFE will vary for each transistor depending on IC
> (Collector Current). So for the same transistor the hFE will vary
> depending
> on what collector current you drive through it. So the range of hFE they
> give is probably not so much an indictation of manufacturing tolerance
> (this transistor is better than that one) but more an indication that ant
> transistor will vary depending on how you drive it.
>
> Of course there are manufacturing tolerances aswell so the range is a
> combination of the two.
>
> The tester probably uses a low IC which will lead to a high hFE. If in
> your application you drive IC to say 1A you would probably find the hFE
> for your transistor would drop down low.
>
> Cheers,
>
> Nigel
>
>
> "ArameFarpado" <a-farpado.spam@netcabo.pt> wrote in message
> news:fucasb$cru$1@news.datemas.de...
>> Hi all...
>>
>> a transistor "BD435" is giving me 440 in hFE test on the multimeter,
when
>> the tecnical data i've found tell me min=40 max=475...
>>
>> does this mean the transistor is really in good shape?
>> can it be busted and still give a good hFE test result on the multimeter?
>>
>> thanks
>> ArameFarpado
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Author: CharlesDate: 18:30 19-04-08
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Leaky transistor or bad instrument or both.
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Author: Phil AllisonDate: 20:21 19-04-08
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"ArameFarpado"
> a transistor "BD435" is giving me 440 in hFE test on the multimeter, when
> the tecnical data i've found tell me min=40 max=475...
** You have it connected wrong or it is a dud.
..... Phil
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Author: Phil AllisonDate: 20:24 19-04-08
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"ArameFarpado"
> i've just made a strange descovery:
> if i leave the base pin not connected, the hFE result is the same.
** You have it connected wrong or it is a dud.
> so i guess this hFE test is not for checking if the transistor is fine or
> busted.
** You have it connected wrong or it is a dud.
Connect a good device correctly and the Hfe reading wil be in the order of
50 - 150.
....... Phil
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Author: ArameFarpadoDate: 16:55 20-04-08
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Em Sábado, 19 de Abril de 2008 23:30, Charles escreveu:
>
> Leaky transistor or bad instrument or both.
got it, thanks
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Author: ArameFarpadoDate: 15:54 23-04-08
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Em Sábado, 19 de Abril de 2008 23:30, Charles escreveu:
>
> Leaky transistor or bad instrument or both.
busted transistor !
replaced and the circuit started to work...
thanks again
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