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Voltage polarity on transistor data sheets

Discussion in 'Electronic Basics' started by [email protected], Dec 16, 2005.

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  1. Guest

    Hi,

    I seem to get stuck on the stupidest things.

    I've been reading the datasheets for two transistors, the MPSA55 and
    the KSP55, and I'm curious if the polarity differences for collector
    current, collector-base voltage, etc are important, because the two
    transistors are "cross-referenced" on quite a few sites. The data
    sheets for the transistors are located at:

    http://www.fairchildsemi.com/ds/MP/MPSA55.pdf
    http://www.fairchildsemi.com/ds/KS/KSP55.pdf

    So for example, on the MPSA55's datasheet, Vcbo is +60V, and on the
    KSP55's datasheet, Vcbo is -60V. I would like to know if the sign
    difference is significant here.

    I assure you that I have no intention of using these transistors any
    time soon, because I know very little about them. However, they could
    be useful at some point in the future, and I am trying to save myself
    $6.50 from digikey by ordering them with some other stuff. So this is
    officially a six dollar question. =)

    Thank you very much for your help.
     
  2. Ralph Mowery

    Ralph Mowery Guest

    As both sheets specify them as a PNP transistor, the - sign does not mean
    anything significant in this case. All one sheet is doing is to put in
    the - sign to denote the collector is negative inrespect to the emitter for
    a PNP transistor. Some sheets will put in the - sign for this reason but
    some will not and expect you to know to hook the collector to the negative
    side of the power supply in respect to the emitter.
     
  3. Rich Grise

    Rich Grise Guest

    Actually, longjohnstuartmill misread teh a55 data sheet - it doesn't say
    +60, it just says 60, so it's OK. :)

    Cheers!
    Rich
     
  4. Guest

    Thanks. That's useful information. =) I never saw it explicitly
    stated anywhere. Maybe that's because everybody knows it
    automatically...

    Heh, my questions are so simple that they're borderline trollish. I
    think it's partly because I don't know anybody that I could ask in
    person, and also because I'm trying to learn using only web sites, some
    old library books (and when I say old I mean they use vacuum tubes),
    and this newsgroup. But it could also be because I'm not too bright.

    Oh well... Eventually I'll either give up or save enough money to take
    some courses.

    Thanks again for your help.
     
  5. Ralph Mowery

    Ralph Mowery Guest

    There are lots of things that are done in electronic circuits that the
    writers are expecting you to know. For example tube filiments are not
    always shown in the schematics or most likely they are not shown with the
    other tube elements but you are expected to find them on the schematic
    grouped with all the filiments connected to the transformer. Same with some
    ICs . The ones that use a positive and negative voltage may or may not show
    the power supply leads. Then they may be grouped together and a bunch of
    capacitors shown with them. You are suspose to know to put the capacitors
    close to the power pins of each IC.

    I had worked with electronic schematics for years and then took a job where
    I also had to look at electrical blueprints. It took a while before I could
    follow the simple prints due to the same problem. Just had to learn what I
    was suspose to know :)
     
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