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  1. #1
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    Type one compensator...why is everybody giving it a phase of -90 degreees

    Surely a type one compensator phase vs frequency Bode plot should always be drawn with -270 degrees phase?
    I mean, -180degrees for the inverting opamp...then -90 degrees for the capacitor in the feedback path...thats -270degrees...so why do most people say the phase is -90 degrees?..its non-intuitive.



    -------------------------------000000------------------------------------
    Same thing tfor the type 2 compensator on page 5 of this...
    http://www.ti.com/lit/an/slva662/slva662.pdf

    ..surely the phase should start off at -270 degrees, not -90 degrees?
    Starting it at -90 degrees ignores the -180 degrees contributed by the inverting opamp...the inversion gives the -180 degrees....why do all articles ignore it?
    Last edited by treez; 8th September 2019 at 20:48.

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  2. #2
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    Re: Type one compensator...why is everybody giving it a phase of -90 degreees

    Often the 180 contributed by the opamp is left out during analysis. It's then accounted for by calculating phase margin relative to -180 degrees, rather than -360.

    So long as it's done consistently, it gives the same answers. Just a preference for some engineers.


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  3. #3
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    Re: Type one compensator...why is everybody giving it a phase of -90 degreees

    Type I is just a single pole integrator. Poles are understood to introduce a 90 degree phase lag or -90 degree phase shift.

    Other phase shifts can be seen as external.


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