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  1. #1
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    Equivalent feed back model transformation

    Hello i am using the two stages amplifier shown bellow into the transimpedance feedback system shown bellow.
    if the system shown bellow i have miiler capacitor and feedback ressistor
    how do i break them into the system shown in the end?
    Thanks.

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  2. #2
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    Re: Equivalent feed back model transformation

    The problem is about extracting Zi, Zo and av from your circuit. As mentioned in your previous thread, an OTA could be better modelled as a current source than a voltage source. But formally, you can still extract a Zo and av.



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  3. #3
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    Re: Equivalent feed back model transformation

    yes , i have modeled it as current source but how to handle miller capacitor in this system?
    Thanks.



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  4. #4
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    Re: Equivalent feed back model transformation

    Miller capacitor is inside the OP, it modifies av and Zo.



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    Re: Equivalent feed back model transformation

    Hello, Thank you very much, i will try to add the miller effect as you said regarding the capactior.
    Regarding the feedback loop ,Why it couldnt be decomposed just like the capacitor we talked about now?
    Why miller laws are not applied in the case of the feedback loop ressistor and instead we do a copy of the ressistor both in the input stage and ouptut stage as shown in the diagram in the first post?
    Thanks



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  6. #6
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    Re: Equivalent feed back model transformation

    Quote Originally Posted by yefj View Post
    yes , i have modeled it as current source but how to handle miller capacitor in this system?
    Thanks.
    Why don't you just use return ratio for the loop? Then you don't have to bother with the miller cap as it effect will be included in the ac gain of the OTA.



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