Phase Shift Oscillator

Discussion in 'General Electronics Chat' started by athandpr, Jul 18, 2011.

  1. athandpr

    Thread Starter New Member

    Dec 3, 2010
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    Hey All,

    I have bread boarded a phase shift oscillator which worked for some time then it doesn't work. I tried the 741, 324, and 339 op amps. The feedback network consists of 1k and 56k. And the phase shift network consists of 0.1u capacitors and 100 resistors. I tried both 3 and 5 phases networks and it worked.

    Each lasted about 3 minutes until I turned the power off (9 volts). Now it doesn't work. I don't know why?

    Thanks.
     
  2. ifixit

    Distinguished Member

    Nov 20, 2008
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    post a schematic
     
  3. athandpr

    Thread Starter New Member

    Dec 3, 2010
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    0
  4. KJ6EAD

    Senior Member

    Apr 30, 2011
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    The circuit wants a dual (+, - and ground) power supply. Are you using a single 9V supply?
     
    Last edited: Jul 18, 2011
  5. athandpr

    Thread Starter New Member

    Dec 3, 2010
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    Yes, I'm using one 9 volt battery. But I have two electrolytic capacitors between the positive and negative forming the ground.
     
  6. KJ6EAD

    Senior Member

    Apr 30, 2011
    1,425
    363
    It works for me in simulation with a generic op amp and a ±4.5V supply (5.88kHz). Try a large value resistance like a 10kΩ resistors in parallel with each of the electrolytics (resistive voltage divider).
     
  7. ifixit

    Distinguished Member

    Nov 20, 2008
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    ±4.5V rails on those old opamps doesn't leave alot of room for the output swing.
     
  8. athandpr

    Thread Starter New Member

    Dec 3, 2010
    11
    0
    Hey folks, thanks for the help. I found out what I did wrong. I had the resistors and capacitors backwards in the phase shift network.

    :rolleyes:

    So when I changed that and made the minor changes you suggested everything worked. I tried 3,5, and 7 phase with no problem.
     
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