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make it clearly beta and betaeff

imagesensor123

 Hi,

    these days i am doing some circuit simulation, and i got confused by beta and betaeff? according to the simple hand calculation equation id=1/2uCoxW/L(Vgs-Vth)^2 or id=1/2beta(Vgs-Vth)^2  or the others. and after simultion, i use the result->print->operation point and i found a betaeff parameter, i think it shold be same with beta, but after calculation id, i found the id(betaeff) is just a half of the id(beta), and how do you calculate the drain current id in saturation region?

Parents

  • First of all, I'm assuming you're talking about the drain current with the devices in saturation - so are they in saturation? Secondly this is dependent upon the model - those simple equations break down for modern devices and modern models are more accurate. The documentation covers the details of the equations used. I would expect that for low level models (e.g. mos3) the equation you have will be a reasonable approximation, but it may not be for bsim4 (say) - but only in the saturation region. Thirdly, why not get the simulator to tell you the id rather than trying to work it out yourself?

    Andrew.

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  • First of all, I'm assuming you're talking about the drain current with the devices in saturation - so are they in saturation? Secondly this is dependent upon the model - those simple equations break down for modern devices and modern models are more accurate. The documentation covers the details of the equations used. I would expect that for low level models (e.g. mos3) the equation you have will be a reasonable approximation, but it may not be for bsim4 (say) - but only in the saturation region. Thirdly, why not get the simulator to tell you the id rather than trying to work it out yourself?

    Andrew.

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