At 01:37 PM 1/11/2010, Josh Koffman wrote: >Hi all. I'm doing a multiplexed LED display for the first time in a >long time. I'm using small displays (0.5" height) that are common >cathode. I haven't decided yet, but I might have a 74HCT4511 decoder >in there, or I might do the decoding in the PIC itself. It'll depend >on how many pins open I end up with. > >My problem is that the transistor I used to use for this sort of thing >(2n3904) doesn't seem to come in an SMT variant at Digikey. I find >this pretty amazing, I wonder if I'm searching for it badly. As others have undoubtedly mentioned by now, replace the "2N" portion of the part number with "mmbt". I'd also consider moving up to mmbt4401 instead of the '3904 - its a beefier transistor that costs about the same as (or even less than) the '3904. Its hard to put into words, but the 2n3906/06 transistors just feel 'softer' than the 2n4401/03. Its really quite noticeable on a scope when you feed a ramped current into the base. I also find that the '4401 survives "Oopses" better than the '3904 - they appear to have much higher peak current ratings. On the other hand, the 2n3904/06 seem to have better high-frequency response. Your mileage may vary . dwayne -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax www.trinity-electronics.com Custom Electronics Design and Manufacturing -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist