Transistor 2N3904

Another newbie Q… trying out this transistor.
I put a LED & 220 ohm in the C-E line on 5V on Arduino (10 mA).
Even without any connection to the Base, the LED is burning! :o
I can get even more mA on the C-E line, the Base unconnected.
Who can explain this to me, tnx.

2N3904 transistor.pdf (66.1 KB)

It is a high gain transistor and the floating base is acting as an aerial.

Ground the base and it should go out.


Even with the base grounded the LED keeps burning... :confused:

I'm not sure what you mean by "the C-E line"... post a schematic.

I mean LED between 5V and Collector, same as here, but other transistor


Maybe it's a breadboard/layout issue.
Maybe it's a bad transistor.
"220 ohms": so it's red-red-brown? (red-red-black is 22 ohms, that might make for some heat etc)

I think we need a picture of how you have set it up.

Tom... :slight_smile: