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higher output MOSFET

Discussion in 'General Electronics Discussion' started by k6ql, Aug 23, 2011.

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  1. k6ql

    k6ql

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    Aug 23, 2011
    My little Retro-40 ( a low power 40 meter transmitter/receiiver) only puts out a little over 1 watt and won't drive my HLA300 ( a solid state linear amplifier) quite hard enough. It originally used an IRF530 which I replaced with an NTE66. because the IRF530 failed and the NTE66 was available locally. Same thing. Do any of you MOSFET experts know of a "hotter" equivalent that might put out 2 or more watts when used as a 7mHz amp. in class C?
     
    Last edited: Aug 23, 2011
  2. BobK

    BobK

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    Jan 5, 2010
    I,for one, do not know what a Retro-40 or an HLA300 is, and I am not inclined to google them in order to answer your question.

    Bob
     
  3. duke37

    duke37

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    Jan 9, 2011
    The IRF530 can switch 14A at 100V, that is over a kilowatt. You need suitable drive and power supply.
     
  4. k6ql

    k6ql

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    Aug 23, 2011
    Hi Bob,
    I edited my question to explain what the devices were that I am using the MOSFET in. I appologize for not making that clear in my original post.
     
  5. davenn

    davenn Moderator

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    Sep 5, 2009
    Hi there .....
    (always good to sign your posts with your name :)

    welcome to the forums

    I agree with Duke,
    The IRF530 and the 540 are still suitable devices
    what is limiting the output is the drive to the device from the previous stage of the transmitter. You may be able to tweek that up a little, BUT DONT
    push it too much, else you are going to loose linearity and your transmissions are going to be very dirty ie. causing splatter etc.
    Your other option is to build a second IRF530 stage and drive it with the other 530 (NTE66) and end up with a good few Watts out. In that case you
    may have to drop back the drive level from the driver stage

    Hey good to see another ham on here :) there are a few of us

    cheers
    Dave
    VK2TDN
     
    Last edited: Aug 23, 2011
  6. k6ql

    k6ql

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    Aug 23, 2011
    Thanks Dave for your reply! I am totally ignorant on these devices! I didn't even think about the driver! Sure makes sense.
    The driver is a TC1412N. Maybe that is what I shoiuld be looking at and not the power mosfet.
     
  7. k6ql

    k6ql

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    Aug 23, 2011
    mosfet deiver

    Would a TC1413N drive the IRF530 a little harder for a tad
    more output? Would it be directly replaceable with a TC1412N?


    Dave
     
    Last edited: Aug 28, 2011
  8. davenn

    davenn Moderator

    13,983
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    Sep 5, 2009
    am not sure there, have never used one. Maybe some one else on here has had dealing with them and could advise :)


    cheers
    Dave

    PS.... most of my activity is at the other end of the spectrum .... above 1 GHz
    I do a lot of microwave gear constrruction and experimentation :)
    see my pages at .... http://www.sydneystormcity.com/microwave.htm for some of the stuff I get up to on the ham bands

    As anyone who knows me well will say... ohh, Dave yeah .. anything below a GHz is DC to him haha
     
  9. duke37

    duke37

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    Jan 9, 2011
    I have not used mosfets at high frequencies but the problem seems to be charging and discharging the input capacitance. The input capacitance changes during the cycle.
    Options
    1. Use a bigger driver or more than one in parallel.
    2. Use a smaller fet with lower capacitance.
    3. Add some antiphase feedback (neutralisation) to cancel some of the capacitance - possibly tricky to set up.
     
  10. duke37

    duke37

    5,364
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    Jan 9, 2011
    Its me again!
    I have driven mosfets with 10V, that has always seemed to be adequate at low frequencies. The driver here is supplied with 6V, is this enough to turn the fet fully on?
    The TC1412N can be stand up to 16V, a few more volts should bump up the current a bit.

    G3VLF
     
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