AM modulation

Discussion in 'Wireless & RF Design' started by atakan_1907, Jan 23, 2011.

  1. atakan_1907

    Thread Starter New Member

    May 18, 2009
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    Hi,
    Im looking for an am modulation technique using opamp. Or using fets, bjts but simple to understand and build.
    Thank you!
     
  2. bertus

    Administrator

    Apr 5, 2008
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  3. atakan_1907

    Thread Starter New Member

    May 18, 2009
    3
    0
    I found this circuit and want to know it works or not?
    OR could you give me a simple one transistor modulator without band pass filter (or coil).
     
  4. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The circuit could work.
    The fet works as a variable resistor depending on the modulation input.
    The usable frequency of the carrier depends on the used opamp.

    Bertus
     
  5. atakan_1907

    Thread Starter New Member

    May 18, 2009
    3
    0
    Thank you!
    A last question; for an 1Vpp input and 2Vpp carrier (or i can divide this if required) which values are the good for resistors?

    I'dont have an oscilloscope at home and there is no possibility to try untill monday. Sorry for asking too much :)
     
    Last edited: Jan 23, 2011
  6. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    The Rds varies with the gate voltage.

    [​IMG]

    I have taken the BF244 as example. (also attached).
    The resistance changers from 100 to 300 Ohms.
    If you take Rf 1K the gain will be between 10 and 3 X.
    I think the carrier mus be a little lower to avoid clipping.

    Bertus
     
  7. atakan1907

    New Member

    Jan 23, 2011
    9
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    Who banned me :)

    I registered again to just thank you.
     
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