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help on second order effect! (Read 2122 times)

kibby Junior Member Offline Posts: 11	help on second order effect! Oct 23^rd, 2009, 8:21am if the function of mos fet in saturation region is used: i=1/2ucw/l(vgs-vth)^2 which ignore the second order effect; to analyse the character of gm''(the second derivative of gm) of a simple full differential amplifier,then is the result helpful for design? or it is unreasonable? why? thx~
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Riad KACED

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Swindon, UK

Re: help on second order effect!
Reply #1 - Oct 23^rd, 2009, 10:42am

Hi Kibby,

Yes, this is a reasonable approach for hand calculation. This is the way every designer goes calculate the first-step transistors. The second stage is to run a Spice level simulation, using Spectre, Eldo, Hspice ... etc. Simulators using models like BSIM3/BSIM4/PSP DO NOT assume any approximation at all, they give you the 'exact numbers' which are likely to be different from your hand-calculation.

Cheers,
Riad.

Riad KACED
PDK, EDA Support Engineer.

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kibby Junior Member Offline Posts: 11	Re: help on second order effect! Reply #2 - Oct 24^th, 2009, 4:23am thank you for your help~
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