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MOSFET I vs. T curve

Discussion in 'Electronic Components' started by John E., Mar 13, 2007.

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  1. John E.

    John E. Guest

    As junction temp increases, r goes up and I goes down, right?

    This must be a misprint:

    (This is IRFM150/2N7224)

    (see fig. 1 & 2 on p. 4). I think these 2 graphs are transposed. The higher
    condition should result in less current, yes?

    Just testing my grasp of the knowledge...

  2. Robert Baer

    Robert Baer Guest

  3. Robert Baer

    Robert Baer Guest

    Page 4 of a GIF??????
  4. Robert Baer

    Robert Baer Guest

    NOT FOUND in DigiKey; either 2N7224 or IRFM150.

  5. John E.

    John E. Guest

  6. chuck

    chuck Guest

    In the graphs you're looking at, you can hold Vds constant (say one
    volt) and compare Id at the two temperatures. It is clear that r
    decreases with increases in temperature. More carriers or something.
    Isn't that a characteristic of all junctions?

    You will find a similar result for the IRF510, for example.

  7. Robert Baer

    Robert Baer Guest

    Look carefully; the figures are correct; it takes a lower Vgs for a
    given Id at 500V (linear current sink region) and one gets a lower
    Rds(on) at a given gate drive (look at Vds=1V, Vgs=7.0V).
  8. Tim Williams

    Tim Williams Guest

    Gate threshold voltage has a negative coefficient, so falls with temperature
    (causing the Vgs = 4.5V curve to move up from about 1.1 to 4.5A). This can
    cause runaway conditions in paralleled linear circutis.

    Rds(on) rises, as can be seen by looking at the saturated region of the,
    say, Vg = 15V curve: at 1V, Ids falls from about 30 to 17A. This causes
    stability in paralleled switching circuits (unlike bare silicon junctions in
    diodes and BJTs, and to a lesser extent, IGBTs).

    It can be seen in Fig.4 that Rds rises about by a factor of 2 from 25 to
    150°C, so my rough reading of the log plot is within reason.

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