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AM modulator

Discussion in 'Misc Electronics' started by exxos, Nov 5, 2004.

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  1. exxos

    exxos Guest

    Hi all,

    Im trying ot build a very simple AM modulator with a small op-amp, bascially
    the carrier is fed into the amp input (as normal audio) then im using a
    transistor to alter the other input side in attempt to alter the volume, I
    can't however for the life of me get it to work.... I've also tried a
    resistor in the carrier line, then pulling the output side of the resistor
    down to ground with the modulation wave, this to me should work though no
    matter what I do it just dont seem to work at all :(

    has anyone got any simple solutions to this ?

    thanks
     
  2.  
  3. exxos

    exxos Guest

    thanks everyone, ive got some ideas of more things to try now,

    chris
     
  4. john jardine

    john jardine Guest

    This modulator circuit is very simple. As the gain control voltage is varied
    from 10V to 0.5V the gain drops from 100X to nothing. (Pretty much any small
    signal transistor will work).

    Gain Control
    .-----o 0.5 to 10V
    |
    .-.
    | |
    2k2| |
    '-'
    Audio In ___ | ||
    (say 10mVpp) .-|___|------o---||----o Audio out
    | 470k | || 0 to 1Vpp
    || ___ | |/ 47uF
    o-||--|___|----o----------|
    || 1k BC546 |> o
    o 47uF | |
    | | |
    '---------------------------|---------'
    ===
    GND

    (created by AACircuit v1.28 beta 10/06/04 www.tech-chat.de)
     
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