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Home > Archive > Electrical Engineering > May 2007 > LED Circuit question
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LED Circuit question
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| I have a question.
I'm using 5-volts as a main supply, a 2N3904, 10k on the base, 500 ohms in
series with a LED. The LED has approx. 2-volt drop and the negative side is
connected directly to the collector with the emitter grounded.
My circuit works fine, however, I expected a Vce of almost 0 volts. I
measured the collector to ground and had about 2.4 volts.
Does anyone know why?
Thanks in advance.
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| Palindr☻me 2007-05-12, 1:25 pm |
| Peter wrote:
> I have a question.
>
> I'm using 5-volts as a main supply, a 2N3904, 10k on the base, 500 ohms in
> series with a LED. The LED has approx. 2-volt drop and the negative side is
> connected directly to the collector with the emitter grounded.
>
> My circuit works fine, however, I expected a Vce of almost 0 volts. I
> measured the collector to ground and had about 2.4 volts.
>
>
> Does anyone know why?
>
Are you sure that it is 10k? Like, measured it?
What's the voltage across the 500 ohms?
--
Sue
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| =?UTF-8?B?UGFsaW5kcuKYu21l?= <me9@privacy.net> wrote in
news:134bta0t73is293@corp.supernews.com:
> Peter wrote:
> Are you sure that it is 10k? Like, measured it?
>
> What's the voltage across the 500 ohms?
>
I haven't had a chance to remeasure everything. I have a relay question
I'll post in a new message.
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Palindr=E2=98=BBme wrote:
> Are you sure that it is 10k? Like, measured it?
>
> What's the voltage across the 500 ohms?
> Sue
And while you are at it try another 2N3904 or measure the gain of the
one you've got.
PS. Make sure you haven't swapped E and C.
Benj
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