Voltage Controlled Phase Shift

Thread Starter

Robin Mitchell

Joined Oct 25, 2009
819
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
 

Kermit2

Joined Feb 5, 2010
4,162
? 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. ?
 

AnalogKid

Joined Aug 1, 2013
10,986
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
 

alfacliff

Joined Dec 13, 2013
2,458
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.
 
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