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Harmonic Content? 555 vs CD4069 oscillator ??

Discussion in 'Electronic Basics' started by royalmp2001, Aug 18, 2005.

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  1. royalmp2001

    royalmp2001 Guest

    Can anyone tell me how the harmonic content of a CMOS 555 squarewave
    oscillator may compare to a 2 hex invertor oscillator from a CD4069.

    I think I heard that the 7555 can produce richer harmonics... but can
    anyone explain if this is true and why?
  2. Andrew Holme

    Andrew Holme Guest

    It depends on the steepness of the edges. If you look at the datasheets,
    and compare their rise and fall times, the device with the faster edges has
    more power in the higher harmonics.
  3. Bob Masta

    Bob Masta Guest

    Not sure exactly what you mean by "richer" harmonics. A perfect
    square wave has only odd harmonics. If you change the duty
    cycle from 50-50, you add even harmonics as well. You might
    want to try a really narrow pulse train.

    Bob Masta

    D A Q A R T A
    Data AcQuisition And Real-Time Analysis
    Home of DaqGen, the FREEWARE signal generator
  4. Ralph Mowery

    Ralph Mowery Guest

    That is the problem. There is no perfect square wave. To do this the
    harmonics would have to extend to infinity. The voltage ouput would have to
    go from maximum to zero in zero ammount of time. Still not possiable in
    real life. Some devices will turn off and on faster than others . This
    makes them "richer" in harmonics than slower devices. The 555 takes longer
    to switch than the 4069.
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