Phase Shifter project

Discussion in 'The Projects Forum' started by bskerr88, Mar 2, 2011.

  1. bskerr88

    Thread Starter New Member

    Mar 2, 2011
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    I have been just playing around with Op Amps and their properties, and have been trying to make a circuit that has a tunable phase shift. I got the idea from this PDF I found of a lab at OSU. I have attached that file where I got the idea.

    I have simulated it in LTspice IV and have been trying to make a prototype with some success. The issues I've having have just been bugging me.. so hoping you guys could help.

    I also have attached the .asc file for it. To play with the phase shift, just change the value of R6 (I have a potentiometer on my breadboard, its cool to see phase shift moving back and forth as you spin it)

    The thing that has been bugging me is I simulated this fine, but my prototype the amplitude is attenuated to ~15% on the output, very annoying. Is there anything I'm doing just glaringly wrong? Could it be my Op amps? I'm actually using INA154's in my prototype.. just what I had around

    My background is more DSP and communication systems.. so I'm not too strong in this area.. Any help is great! Thanks guys
     
  2. Audioguru

    New Member

    Dec 20, 2007
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    You cannot use an INA154 as an ordinary opamp.
     
  3. bskerr88

    Thread Starter New Member

    Mar 2, 2011
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    Can you elaborate why?

    What op amp would you suggest? Would be nice to have the same pinout... :D
     
  4. Audioguru

    New Member

    Dec 20, 2007
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    The IN154 differential amp IC is obviously not an ordinary opamp and cannot be used in your circuit. Why can't you see the difference??
     
  5. Teri

    Member

    Apr 3, 2009
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    Use your simulation probe to determine what the voltages should be at different points in the circuit and compare them to the voltages in your prototype. Is the loss in your first op amp or the second or both?

    It might help to use a shorter time period in the simulation so you can see what is happening better: .tran 0 .1 0 .001
     
  6. bskerr88

    Thread Starter New Member

    Mar 2, 2011
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    0
    I had a different op amp laying around that actually had the same pin out! I tried the TLV271 and it worked much better, but the output was clipped to +/- 1V with a +/- 5V supply.

    Is it my op amp again? You guys have been super helpful thanks!
     
  7. Audioguru

    New Member

    Dec 20, 2007
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    The TLV271 is another very weak Cmos opamp with very low output current.
    What is its load and power supply voltage?
     
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