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Beginners question

Discussion in 'Electronic Basics' started by [email protected], May 15, 2005.

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  1. Guest

    Hi - I am trying to get a handle on some switching speed concepts -
    I beleive it is correct that the faster a signal switches the closer to
    a square wave it becomes and therefore the more harmonics it contains
    ?? So just how fast must it switch to contain 'all harmonics' ?

    Thanks in advance,
    El Squid
     
  2. Andrew Holme

    Andrew Holme Guest

    The short answer is: instantly.

    The long answer is: all signals are bandwidth-limited. No signal contains
    an infinite number of harmonics, and no signal has zero rise-time.

    Also, it isn't just the number of harmonics which determine waveform shape,
    but also their relative amplitudes.
     
  3.  
  4. Matt Flyer

    Matt Flyer Guest

    You are correct. One of the implications of this is that faster the
    signal transitions (i.e. shorter rise or fall time) the higher the
    significant energy content of the higher harmonics that your circuit
    must handle. As a rule of thumb, beyond a certain point, which alot of
    times can be aproximated as .5/Trise, you no longer need to worry about
    the harmonics. A second implication of this conecpt is that it is not
    posisble to generate an ideal square wave with physically realizable
    components.
     
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