BJT BASED SINE WAVE OSCILLATOR

Discussion in 'Homework Help' started by Amandeep Singh, May 9, 2009.

  1. Amandeep Singh

    Thread Starter New Member

    May 9, 2009
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    I want to Design a sine wave oscillator using BJT which should generate frequency between 150Hz to 350 KHz and also write the PSpice programme for the same.
    Is there anybody who can help me ??
     
  2. Amandeep Singh

    Thread Starter New Member

    May 9, 2009
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    Its Urgent.
     
  3. steveb

    Senior Member

    Jul 3, 2008
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    Define urgent. How many days before your project is due?
     
  4. CDRIVE

    Senior Member

    Jul 1, 2008
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    What would be really impressive would be to reproduce the Hewlett Packard historic (HP-200A) using FETs and solid state approach to the large variable cap. If my memory is correct, each section of a ganged cap (like the one shown in the photo) were about 365pF max.

    http://oak.cats.ohiou.edu/~postr/bapix/HP200C.htm
     
  5. Wendy

    Moderator

    Mar 24, 2008
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    Anyone remember the 60° oscillator? I remember it from college, each RC leg shifts the frequency 60°, 3X60° is 180°, and since the transistor oscillator shifts the freq another 180° you have positive feedback.

    [​IMG]
     
  6. CDRIVE

    Senior Member

    Jul 1, 2008
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    I'm approaching a point in my life that nostalgic stuff like this beats sex. :D
     
  7. SgtWookie

    Expert

    Jul 17, 2007
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    Yeah, it's fun stuff. ;)

    Unfortunately, I think our OP forgot to include that it's a homework assignment, and as such, we can't do the work for him - he's got to 'noodle it out' for himself.

    Can someone move this thread to the Homework Forum please?
     
  8. CDRIVE

    Senior Member

    Jul 1, 2008
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    We have the same policy on VB Forums and it's a good one. Somehow I missed the tell tales in his post though.
     
  9. Wendy

    Moderator

    Mar 24, 2008
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    I left the values off so he could go through the exercise. I figure everyone has seen this oscillator, or will.

    VB Forums?
     
  10. DonQ

    Active Member

    May 6, 2009
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    Yeah. Except I know it as the "phase-shift oscillator". The phase shift doesn't need to be the same at each stage, the oscillator will find the frequency where the combined phase shift totals 180 and go happily on its way.

    I think, even with equal value components, the phase shift per stage is not equal because of the parallel paths being different on the different stages, and the loading of the gain component on the last stage. Some manipulation of the values at each stage can make it closer, but "60° oscillator" is probably still optimistic.:D
     
  11. Wendy

    Moderator

    Mar 24, 2008
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    Yep, but when you teach theory you don't always get into the messy details, those come later. When I was learning this stuff they didn't have SPICE, and the computer we got to use in the electronics class was a PDP brought in a trailer (a big trailer).

    Like I said, it's been 30 years. The circuit stuck, even if the name didn't.
     
  12. DonQ

    Active Member

    May 6, 2009
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    Best I can remember, I learned of the "Phase shift oscillator" in the fall of 1972! (Don't tell anybody :D). Then, they taught both the tube and the semiconductor versions of circuits.
     
  13. viip

    Member

    Apr 16, 2009
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    How messy it would be to work with those tubes..These lil opamps chips are the best and cute too:D

    And pspice is old thing..why dont you go with simulation tools like multisim..
     
  14. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    multisim.. is a version of "spice". I highly doubt the makers of multisim re-created all the available models for their component list.

    Vacuum tubes are not messy ... well, they could be if you grabbed the 21,000 volts and you and/or your body made the mess. :D

    Build a phase shift oscillator with multisim. Substitute different OpAmps and see the frequency changes. It's probably as messy as vacuum tubes. :D
     
  15. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
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    You know, I actually HAD one of those, years ago! I sold it at a ham flea marker. Just hope it found a good home. :)
     
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