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Newbie question: Identifying Transistors

Discussion in 'Electronic Basics' started by James Howe, Oct 31, 2004.

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  1. James Howe

    James Howe Guest

    I recently purchased a 'grab bag' of components which included a bunch
    of transistors. Most of the transistors are what I think of as a
    typical transistor, black case, flat on one side. Many of these
    transistors have no markings on them at all. Others say things like
    "NTCMP S3706" or "NTC P N4916". Is there a reasonable way to learn
    more information about the specifications for these transistors?


    James Howe
  2. Gareth

    Gareth Guest

    The first thing I would try is typing the numbers on the marked devices
    into Google. If that doesn't work try truncating the part number as the
    last few characters could just be a batch code, date code of package
    options. If you recognise the manufacturer you could go to their
    website and see if you can find the part there.

    Here are the websites of some transistor manufacturers:

    For the unmarked devices it could be very difficult. There are many
    electronic devices which have three legs so these parts may not even be

    Good luck.


  3. BobGardner

    BobGardner Guest

    Many of these
    You can tell if its pnp or npn with an ohmmeter.... if you know the pinout....
    red on base, black on emitter showing some lo ohms... its npn

    For the ones with numbers, type em into google... mps3706 sounds like a
    motorola (or On semiconductor) number, 2N4916 might be a vaild number...
  4. Rich Webb

    Rich Webb Guest

    Radio Shack has a handly little (and inexpensive) tester that will
    classify common small signal transisters by type (NPN, PNP) and flag the
    base and collector leads. Part # 22-330. Not sure that this is in their
    current catalog but you might be able to find a store with one.

    Also, many general-purpose multimeters have a socket that accepts a
    transistor and that then reads out hfe (more or less). It helps to know
    the type and CBE order, though, so even with one of these the little RS
    gadget is helpful.
  5. Squidster

    Squidster Guest

    NTC is a Taiwanese semiconductor manufacturer; Nanya Technology
    (, and probably OEMs for Motorola/ONSemi for the
    MPS3706, which is Motorola's original implementation of the generic
    2N3706. Datasheet is here:

    PN4916 is originally from Fairchild, in your case is probably OEM-sourced
    implementation from NTC too.
    Datasheet is here:

    It all boils down to exposure and experience. Just like everybody knows
    what brands of PC exist in the market. You'll soon learn what are the
    dominant seminconductor manufacturers are there...
  6. Active8

    Active8 Guest

    In a male or female voice? That's a big clue.
    Besides those other good suggestions, electronics parts stores (real
    ones) have cross-reference guides. They gave me one (the NTE book) a
    long time ago. Note, the specs of the original and replacement might
    not be an exact match, but hey, it's a grab bag :)

    Maybe Bainsville Electronics in b'more (or someone like that) has a
    cross-ref search on their web-site.
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