Choosing a transistor


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  1. #8
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    Ive been trying some more values in the search at digikey and its started to give me no results for what i want. I had a quick look through the transistors at rapid and found one that looks like it might work. 2N3702 40V TO92 PNP GEN PURPOSE TRANS RC. The most current the LEDs would draw should be 510mA. The datasheet for this transistor says "Collector Current - Continuous 500 mA". It wont be used continuously. It will only be on for 1/4 of the time at the most. It also says "Collector-Emitter Voltage 25 V". I was planning to use 12V for the LEDs (depending on further tests). I am using 12V at the moment but it might be because im using NPN transistors. When i put the correct PNPs in then 12V might be too much for them. The datasheet doesnt mention darlington pair so i assume its just a normal transistor. I think that means that the output might be slightly lower than if it were a darlington pair. That might be a good thing if the 12V is too much.

    Edit: That one is also in a TO92 package. It doesnt matter too much but those would fit best on the PCB. Things like the TO220s that ive seen are way too tall. There is also a height limit on the PCB of about 8mm
    Last edited by The Master; - 29th September 2008 at 10:11.

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