Voltage Controlled Phase Shift

Discussion in 'General Electronics Chat' started by Robin Mitchell, Nov 13, 2014.

  1. Robin Mitchell

    Thread Starter Well-Known Member

    Oct 25, 2009
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    Hi all,

    How would I go about designing a voltage controlled phase shift?

    I know that you could use an active amplifier (op amp configuration) and use a FET as a voltage controlled resistor with a capacitor to adjust the cut off frequency but thats very ugly. For one, different FETs have different characteristics so I dont want to be designing a circuit specific to a single FET.

    Any ideas?

    All the best,
    Robin
     
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    ? use an op amp in a capacitor multiplying mode and vary the gain(capacitance) of it with a digital pot in the place of a gain resistor. the shift would be limited in range though. ?
     
  3. alfacliff

    Well-Known Member

    Dec 13, 2013
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    what frequency range?
     
  4. Robin Mitchell

    Thread Starter Well-Known Member

    Oct 25, 2009
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    Well the range would be the human hearing so about 16Hz to 20kHz
     
  5. alfacliff

    Well-Known Member

    Dec 13, 2013
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    search "flanger" a phase shift sound effect for guitars.
     
  6. crutschow

    Expert

    Mar 14, 2008
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    Robin Mitchell likes this.
  7. AnalogKid

    Distinguished Member

    Aug 1, 2013
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    Can you clarify your requirement? A phase shift of xx degrees across all frequencies, or a time shift of xx milliseconds? The two are very different. If you want a variable time delay, which equates to a different phase shift at each frequency, then a bucket brigade or charge coupled device will do it in the analog domain, or an A/D-shift register-D/A in the digital domain. A voltage-variable delay line over 11 octaves would be tough.

    ak
     
  8. alfacliff

    Well-Known Member

    Dec 13, 2013
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    another way would be a synchro control transformer, an odd thing looks like a motor, with two stator windings 90 degrees apart and a single rotor winding. commonly used to provide the x and y deflection for radar indicators.
     
  9. Veracohr

    Well-Known Member

    Jan 3, 2011
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