This relay kit uses a 3904 transistor to activate it. I'm looking for a smd variant of this. Searching digikey, for "3904 SMD 200mA" I come up with 24 differ ones. I'd like to get one that's 'common' and that would be a good choice for this type of application (used to switch something one from an Arduino when the Arduino pin out current isn't quite enough.
Thanks.
Sounds like you're looking for a piece of hay in a haystack. Don't be overwhelmed by the selection; just take whatever looks OK.
Matches 2n3904 closely: http://www.digikey.com/product-detail/en/MMBT3904,215/568-4510-1-ND/1944320
Thanks that looks great. It'll be nice to have something like that on hand. I'm assuming it will work for lots of things, like turning on LED's, etc.
The part you want is an MMBT3904 (SOT-23) or a PZT3904 (SOT-223) both are SMD and the PZT3904 if mounted properly with some copper for a heat sink will dissipate 1 watt while the MMBT3904 is in an SOT-23 case and will dissipate 325 mw of power. The MMBT2222A will handle 600 mA of collector current however the total dissipation is 325mW. The SOT-23 package is limited to 325mW of power dissipation due to limited ability of the package to conduct heat away from the transistor pellet.
This is the link I use for data sheets, you might find it more useful than Google (read Guess).
MMBT2222A Datasheet pdf - Small Signal Transistor (NPN) - Comchip Technology. use the link as is there is a search box at the top for your queries.
I have a folder on my desktop and every time I reference a data sheet from the link I save a copy of it to the folder. This has been Very handy for me in doing the stuff I do. It is the source of the data sheets I post here.
Doc