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opamp sine wave oscillator

Discussion in 'Electronic Design' started by Inventor, Feb 4, 2008.

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  1. Inventor

    Inventor Guest

    Hi, hope I'm posting to the right place. I created a nifty little
    sine wave oscillator. I have no plans to patent it just want to tell
    the world about it cause I think it's pretty cool. You can download
    the pdf file here:

    http://www.freedomodds.com/osc/

    I like it for lots of reasons, but what's more important is peer
    review. So what do you think of my nifty little oscillator?
     
  2. Jim Thompson

    Jim Thompson Guest

    WHERE is the invention ?:)

    ...Jim Thompson
     
  3. Inventor

    Inventor Guest

    It is in the pdf file linked to by the first sentence on the page.
    The page says:

    The Oscillator.pdf file contains a description of my new oscillator.
    Enjoy.

    That Oscillator.pdf is the like to it. Guess I should make that more
    obvious, huh?
     
  4. Jim Thompson

    Jim Thompson Guest

    I read the PDF. I fail to observe any invention. Please describe the
    improvement.

    ...Jim Thompson
     
  5. Inventor

    Inventor Guest

    Well, there are a few. For one, it is a single-opamp oscillator. It
    does not have multiple opamps, transistor feedback stages, light
    bulbs, or other such stuff to make it work. For another, it is
    amplitude stabilized by the supply rail, which is nice. Plus it can
    operate as an amplitude modulator. It is also a class of circuits,
    not just a single circuit, based on some design principles. Those are
    some of the improvements.
     
  6. Wien bridge oscillators with one opamp and no other semiconductors have
    been around already.

    http://www.ti.com/sc/docs/apps/msp/journal/aug2000/aug_07.pdf

    And I saw in your pdf the oscilloscope trace. It appears to me that
    your supply rail amplitude stabilization involves some clipping. Did you
    try listening to it through an amplifier and a loudspeaker? I have heard
    what a sine wave looking like that one sounds like, and I would not mind
    one little bit using an incandescent lamp to fix that.

    - Don Klipstein ()
     
  7. Jim Thompson

    Jim Thompson Guest

    With clipping distortion what's the value?

    People who rave about what they've done with a single OpAmp are in the
    same class as those who make a single-transistor LED flasher ;-)

    Come back when you have a sine-wave oscillator with better than 0.01%
    THD.

    ...Jim Thompson
     
  8. Inventor

    Inventor Guest


    The solution to that is to use the non-inverting tap, which has much
    lower harmonic content (see the other photo).
     
  9. John Larkin

    John Larkin Guest

    The pseudo-scientific-paper format is interesting, but the style and
    syntax are jarring in that context.

    The oscillator itself is trivial. Hewlett did a better job in 1938.

    John
     
  10. Winfield

    Winfield Guest

    Our new 2-opamp "AoE oscillator" (a modified
    Wien bridge made with two inverting opamps and
    G=2) has about 0.0002% (2ppm) distortion, IIRC.
     
  11. Jim Thompson

    Jim Thompson Guest

    But just wait until you see the "Inventor" PhD dissertation.

    Bwahahahahahahaha ha ;-)

    ...Jim Thompson
     
  12. MooseFET

    MooseFET Guest


    It has way too many parts in it.

    10K
    -------/\/\------------
    ! !
    +-------!-\ LT1013 !
    ! ! >--------+---+----- Out
    ! GND--!+/ !
    === === 1.0u
    ! 0.1u !
    GND GND
     
  13. As opposed to not enough parts?
     
  14. John Larkin

    John Larkin Guest



    Your circuit has way too many parts.


    John
     
  15. Inventor

    Inventor Guest

    Thanks for your input, John. It does seem like a lot of parts, but
    when you look at the alternatives, in most cases, it is fewer parts.
    But yeah, four RC's for a single oscillator does seem like a lot. If
    you want fewer parts try the LC oscillator described later in the
    paper I guess.
     
  16. John Larkin

    John Larkin Guest

    The "alternatives" have more parts for reasons. If you just let an RC
    oscillator build up amplitude until it clips, you get a lot of
    distortion. If you clip just a tiny bit, it's marginal to oscillate at
    all.

    Hewlett's lightbulb was a nonlinear element with a long gain time
    constant that rolled off the gain to get stable amplitude with low
    distortion.

    An LC oscillator can be made with mimimal parts and low distortion,
    but it's hard to tune over a wide range.

    All this was understood 70 years ago.

    John
     
  17. Eeyore

    Eeyore Guest

    It'll need to be better than 0.001% to interest me !

    I imagine that 'Inventor' isn't familiar with state of the art.

    Graham
     
  18. Inventor

    Inventor Guest

    Well, then maybe the circuit is not for you. You know, I am really
    quite surprised at all the negativity in these responses. I figured
    out something interesting, I wrote it up, and I posted it on the web
    for you to enjoy. I'm not asking for anything from anyone other than
    a plain, simple peer review and I've gotten some of that, thank you
    very much. The circuit might prove very useful, it might not. I had
    fun with the process of discovery so it was a pleasant, positive
    experience for me. Why don't we all play nice for a change?
    Thanks!
     
  19. [...]
    I thought your article itself was quite interesting, nicely laid out
    too. I think some people are having a problem with your perceived
    claim to "inventing" something new. These circuit arrangements are no
    doubt obvous and well known for decades, to those here more
    experienced. And for the stated goal of a sine wave oscillator there
    are better solutions.
     
  20. Inventor

    Inventor Guest

    Well, I can't really be certain, but I kind of thought there was
    something new here, yes. I thought that stuff about using the inverse
    dual voltage divider on opposite sides of the circuit was new, the
    fact that it's a whole family of oscillators not just one was new, and
    features like the amplitude stabilization and amplitude modulation
    were new as well. I think people are reminded of familiar circuits by
    the new circuit, and then they reply: "that's been done before!", but
    at this point I'm still thinking there is novelty here. If it's an
    old familiar circuit, would someone please post a reference, perhaps
    an existing web link?
     
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