calculating power mosfet bandwidth

Discussion in 'General Electronics Chat' started by yourownfree, Sep 26, 2009.

  1. yourownfree

    Thread Starter Active Member

    Jul 16, 2008
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    How can I calculate the bandwidth of a power mosfet? I would like to use them for making rf power amplifiers. I would like to know so I can calculate the frequency that the power starts to drop off. Also would like to know how can I figure out using the specs and dissipation what I might expect to get for output power. I tried using a formula I saw to calculate the bandwidth but I failed to calculate it correctly from the specs I saw. An example would be great, or know where I can read and study up on the subject? I am not a student or in school. I am an older hobbyist as you can see by my profile. I do have a ham radio license.
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    You'll have a hard time getting a power MOSFET amplifying signals past a few hundred kHz; it's the total gate charge that's the killer.
     
  3. yourownfree

    Thread Starter Active Member

    Jul 16, 2008
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  4. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    The manufacturer should spec it. I doubt any calculation will be accurate, you have to measure it.
     
  5. yourownfree

    Thread Starter Active Member

    Jul 16, 2008
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    0
    I wish I could locate the article. It had to do with on time and off time speed. Using those values would give an idea. My worries were the capacitance at the inputs and outputs as well, but looking at the 300 watt specs those values are high. I found another amp 400 watt. Yeah probably right, just need to make a test circuit and just drop in a mosfet and test it I guess.
    I could just utilize what they are already using too. I actually found many more articles on people building these and their schematics etc. I'll keep reviewing post though. Thanks for the replies.
     
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