Re: IC高手麻煩幫忙解答一下

[pow (體脂肪35%)]

※ 引述《kobetwo (高跟美腿控)》之銘言：
: ※ 引述《pow (體脂肪35%)》之銘言：
: : http://www.mosis.com/Technical/Testdata/tsmc-035-prm.html
: : Look for the column: K' (Uo*Cox/2)
: : Also,
: : In the SPICE models:
: : U0: Channel mobility (unit:m)
: : TOX: gate oxide thickness (unit:cm^2/V/s)
: : You can calculate COX=Permittivity_of_OX / TOX
: : *be careful of the units conversion
: 我之前設計OP也有這個問題,我發現W/L比會影響到MOS的模型
: 這些模型例如有pch.1 ~...~ pch.11
:               nch.1 ~...~ nch.11
: 而每個模型的U0都不盡相同
: 如果想要把U0給定,就是先決定用某個模型,那麼W/L比值需要定在此模型容許範圍裡
: PS.難怪做類比電路需要很多經驗,電子學觀念通還是不夠的   囧
actually...those are just parameters for modeling
you should be able to come up with some method to set up a test circuit
to get the W/L you need.

Example:
You want to make a tail current source for a diff-pair.
1. Put down the NMOS with
   Width= variable Wn1
   Set the Length=3*minimumL to get around channel length modulation
2. set the minimum VDS
3. set the range of VGS
4. Sweep Wn1 and VGS to get IDS you want

This way you don't need to do hand calculation 'cause when you draw the test
circuit and figure out what data you need to measure, you are writing down
an equation (or set of equations) and let the software help you
"solve" the equation(s). But you must have a very good understanding of
how the circuit works. Or you'll be employing "shot-gun method" for larger
circuit, such as an Op Amp. Setting everything an variable and hope you can find
an optimized performance is not going to work. You would rather spend lots of
time understanding how circuits work and setup the test circuit than randomly
walking in the sea of circuit topologis adn variables.

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