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    mosfet what is typical gm value

    e. g Width and Length etc

    •   Alt2nd February 2005, 00:58

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    w/l ratio typical value

    Typical value of MOSFET for what? W/L = 10u/0.18u, 1u/0.18, 10u/0.6u, 1000u/0.6u

    minimum dimensions are set by technology design rules. Max - whatever.
    Question like that does not have answer.....



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    mosfet typical length analog design

    Thanks Teddy. Im trying to design an analog delay line as my undergraduate project. my supervisor has asked me to work out the W/L of the CMOS 0.35u. I believe chosing the W/L can vary the transconductance and/or reduce the Vgs drop across the Mosfet. am i correct?

    Thanks



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    Re: what is the typical value of Mosfet?

    You'll have to find out what your target gm is and plug in the figures into the formula to get an approximation of the W/L. Your Vgs and Vds has to be large enough to keep it in saturation too. Consult your 0.35um process manual for other figures. Your min. length should be 0.35um.


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    what is the typical value of Mosfet?

    how do i find a target gm?



    •   Alt2nd February 2005, 11:41

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    Re: what is the typical value of Mosfet?

    I personaly would start from the "Spec". What should be the minimum delay, max delay, is it variable delay or fixed delay, should it be differential or not?
    What size are your I/Os or is it just block without any output spec? (VOH, VOL etc)

    You should probably make a calculation of the "stage" delay ( I am sure you had it during the course) and based on the calculation and the spec. you should be able to figure that out.

    If you want just to put something quick together I would say 5/0.35 seems quite reasonable .... (though a little big)


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    •   Alt2nd February 2005, 19:49

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    what is the typical value of Mosfet?

    Thanks, what I meant by the delay line is actually an analog shift register. it really is just connecting a bunch of S/H circuit and a few buffer together.

    say I want to make a switch for the simple S/H circuit what gm should it be?



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    what is the typical value of Mosfet?

    It depends on the speed requirement.



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    Re: what is the typical value of Mosfet?

    Quote Originally Posted by ug02048
    Thanks, what I meant by the delay line is actually an analog shift register. it really is just connecting a bunch of S/H circuit and a few buffer together.

    say I want to make a switch for the simple S/H circuit what gm should it be?
    Finding a MOS switch size for a S/H is a different kettle of fish. In this case, you won't need to know the gm. You should concentrate on the ON resistance of the MOS. Try looking up Phillip Allen's book for MOS switches. You also don't want to make it too big, otherwise you'll get clock feed through.


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    Re: what is the typical value of Mosfet?

    MOSFET is voltage controlled device and its properties mainly based on W/L ratio i'e width and length.L shows the technology you are using



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    Re: what is the typical value of Mosfet?

    length of the mosfet totally depends upon the technology u r using.then according to specification/s u can determine the width of the transistor



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    Re: what is the typical value of Mosfet?

    Quote Originally Posted by Teddy
    Typical value of MOSFET for what? W/L = 10u/0.18u, 1u/0.18, 10u/0.6u, 1000u/0.6u

    minimum dimensions are set by technology design rules. Max - whatever.
    Question like that does not have answer.....
    that's not true. minimum length is rarely used in analog design. also, many if not most has wmin, wmax , lmin, lmax for the model parameter fitting...



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    what is the typical value of Mosfet?

    the length of a typical transistor.



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