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  1. #1
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    A zero at folded cascode apmlifier

    Why there is a zero by counting the gain from the input to node2. Why the gain at high frequency is gm1/gm2? Thanks.


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    page 10.

    http://ece.tamu.edu/~spalermo/ecen47...ascode_ota.pdf

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  2. #2
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    Re: A zero at folded cascode apmlifier

    Because looking into the source of at low enough frequencies you see big resistance and gain is defined by ro1||ro5. When CL reduces the impedance at the output, then looking into n2 you start seeing 1/gm2 and you get the behavior shown on the plots.


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    Re: A zero at folded cascode apmlifier

    Quote Originally Posted by sutapanaki View Post
    Because looking into the source of at low enough frequencies you see big resistance and gain is defined by ro1||ro5. When CL reduces the impedance at the output, then looking into n2 you start seeing 1/gm2 and you get the behavior shown on the plots.
    The above should read " Because looking into the source of M2 at low enough frequencies...."


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    Re: A zero at folded cascode apmlifier

    That's really helpful. Could you please explanate the zero? Why there is a zero and why the zero location is that? Thank you.



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    Re: A zero at folded cascode apmlifier

    Here is a short explanation


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    Re: A zero at folded cascode apmlifier

    Wz is a zero location.

    I didn't know what the zero location calculation can also use the gain-bandwidth constant relationship to obtain. Thanks.



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  7. #7
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    Re: A zero at folded cascode apmlifier

    The gain bandwidth relation just relates two frequencies on a + or - 20db/dec response. It doesn't care if you call one frequency a zero or a pole or just pick two frequencies on the slope.


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