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Frequency Multiplier?

  1. Apr 13, 2007 #1
    Hello All,

    I've been working on making a special three-channel pulse circuit that has three harmonic outputs using a 7473 flip-flip IC. I am presently driving it with my function generator, which only goes up to 1MHz and I can divide the frequency down to 500 kHz and 250 kHz using the flip flip chip.

    However, I am wondering if there is any kind of IC that does just the opposite of the flip flop, meaning that it doubles the frequency that you put into it? Ideally, I want to be able to control the thing with my function generator but be able to go up to higher harmonics then I am capable of reaching at the moment.

    Jason O
  2. jcsd
  3. Apr 13, 2007 #2
    I don't know anything off the top of my head, but conceptually, you can use your function generator to make a square wave, and then use a narrowband amplifier to amplify the higher harmonics.
  4. Apr 13, 2007 #3


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    Science Advisor
    Gold Member

    Build a class C amplifier and tune the tank circuit to a harmonic of the input frequency.
  5. Apr 13, 2007 #4
    Is there any way to make it variable? I made the flip-flop circuit so that I could dynamically vary all three frequencies by varying the signal generator input.

    Attached Files:

  6. Apr 16, 2007 #5


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    Staff: Mentor

    What you are describing is a phase-locked loop (PLL):


    You make a PLL with a voltage-controlled oscillator (VCO) like a 74HC124 or more modern one, along with a feedback/divider circuit that locks a multiple of the basic oscillator frequency onto the fundamental frequency. Like, you could make a x8 PLL to give you an 8MHz output waveform that is locked to (and based upon) the 1MHz input frequency.

    PLLs are a very interesting function block, and very useful in the real world. I'd encourage you to do some reading, and to build a few with discrete parts like the 74HC124 and flip-flop dividers. Pay particular attention to the math behind the stability of the feedback path, and the startup/lock times and phase jitter calculations.

    Good project, Jason.
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