Pullup or current limiting

[Wong]

Hi,
If a 5V source is connect to a resistor, then a LED, then to the
collector of a transistor, in series connection.
I guess this must be a current-limiting-resistor, right ?

 

[Bernhard Roessmann]

Wong wrote:

Hi,
If a 5V source is connect to a resistor, then a LED, then to the
collector of a transistor, in series connection.
I guess this must be a current-limiting-resistor, right ?

Yes.


Regards,

--
Bernhard Roessmann
Don't Fear The Penguins!

 

[ETC Mitchell]

tatto0_2000@yahoo.com (Wong) wrote in message news:<509bfe22.0405250425.515f440d@posting.google.com>...

Hi,
If a 5V source is connect to a resistor, then a LED, then to the
collector of a transistor, in series connection.
I guess this must be a current-limiting-resistor, right ?

Definitely. Most LED's require a minimum of 10 mA of current and a
maximum of 20 mA of current to operate. Anything less than 10 mA will
be too dim to see, and anything above 20mA with damage the LED.