Building all pass filter

Thread Starter

DaniKowa

Joined Jul 1, 2021
46
Hi,

please some question for you.

1) Supposing ti build a all pass filter to correct a phase signal (ex -90° to 0°or -180) .Is this correction is still fixed for all frequencies passing through the filter or not?

2) Is this filter buildable with discrete components instead the opamp?
 

crutschow

Joined Mar 14, 2008
28,201
.Is this correction is still fixed for all frequencies passing through the filter or not?
No, it varies with frequency.
Is this filter buildable with discrete components instead the opamp?
Yes.
But the opamp circuit will likely give a more ideal response.

Below is the LTspice simulation of an all-pass op amp filter:
Note that the phase varies from 180° to 0° as the frequency increases, while the amplitude is essentially constant.
If you interchange R1 and C1 the phase will vary from 0° to180° as the frequency increases.

1633885756392.png
 
Last edited:

Thread Starter

DaniKowa

Joined Jul 1, 2021
46
Ok a will try to simulate. I'im not sure but sometime ago have found a circut made by two opamps that permit to vary the phase with two resistor instead one resistor and one capacitor. May be possible? Thanks.
 
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