Cant oscillate sine wave from "bubba" oscillator

Discussion in 'The Projects Forum' started by LFU, Apr 3, 2010.

  1. LFU

    Thread Starter New Member

    Apr 3, 2010
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    Hey,
    Mt project is DC/AC inverter.
    In this project i am using a "bubba" ocsillator as a sine ref circuit.
    Whan i am tring to simuliting this ocsillator using "Pspice" i get a DC wave at the outputs.
    whan i have wireup'd this circuit in reality i have succssfully saw the sine wave.
    why i cant see sine wave in Pspice?

    thanks!
    Liran
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    What is your simulation start and stop times, and what is your step?

    Do you skip the initial operating point?

    R7 and R8 should be adjusted for about 1.2v out (R7=9k, R8=1k), and connected directly to U6 pin 3. Remove U5C. A TL08x opamp can't get within 3v of the negative rail, so it's not really suitable for a voltage follower for a voltage that close to the negative rail.
     
  3. Audioguru

    New Member

    Dec 20, 2007
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    Your schematic has too many ground wires, supply wires and crossed wires all over the place. If you use ground symbols, use + supply symbols and uncrossed all the crossed wires then it would look neat and tidy like the one you tried to copy.
     
  4. Wendy

    Moderator

    Mar 24, 2008
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    What is your op amp?

    What is the resonant frequency?
     
  5. Audioguru

    New Member

    Dec 20, 2007
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    The schematic shows the antique LM348 (a quad 741).

    Texas Instruments sine-wave oscillators document says 1.72kHz when a fast opamp is used.
     
  6. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    He needs a different op amp. LM348 won't work with 1.2V on the inputs either.:(
     
  7. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    TLV 2474 was used in the bubba oscillator in TI's Op Amps for Everyone.

    on edit ...

     
    Last edited: Jun 21, 2010
  8. Audioguru

    New Member

    Dec 20, 2007
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    If you do not power it properly or if you short its output with an impedance less than about 1k ohm then the oscillator will not work.
    An 8 ohm speaker as its load shorts its output. Use a power amplifier to drive a low impedance speaker.
     
  9. Y2J

    New Member

    Feb 17, 2011
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    I have Dc/Ac inverter circuit that same with LFU, using 1r2110 as gate driver of IRF20n50k and bubba oscillator as oscillator. I tried simulate it using PPSPICE and Proteus but it did not functioning. Does anybody here know how to solve this? I doing my project upon this topic. Need help. TQ.
     
  10. SgtWookie

    Expert

    Jul 17, 2007
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    IRF20N50k does not seem to be a good part number.

    Trying to use a "bubba" oscillator or other sine wave oscillator as an input to an IR2110 gate driver won't work; you would need other circuitry.

    You have not posted an image of your schematic, so we have no idea what to tell you.
     
  11. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    I thought maybe he was trying to use the Bubba oscillator as the reference for a true sine wave output inverter.
     
  12. Audioguru

    New Member

    Dec 20, 2007
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    Yes it is.
    But it uses the wrong opamps and is biased wrong.
     
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