difference between the calculation by hand and simulation

[e_fever_l]

hi,every one.I'm a beginner .I have a question,how big difference is acceptable between the calculation by hand and simulation by computer? 20%,50%,or more? such as calculate the current of a simple current mirror,0.6um cmos.use Id=1/2CoxUnW/L(Vgs-Vth)(Vgs-Vth)*(1+lambda*Vds).
thanks a lot.

 

[amey_0309]

thnx 4 info!!!

 

[pravin_dwaramwar]

Re: difference between the calculation by hand and simulatio

Dear amey_0309
Hand calculation takes simple mos model (level 1) into consideration.
On the other hand computer simulation takes complex model into consideration,while doing calculation.
Difference betn results are very less than 5 to 10 %.

 

[e_fever_l]

Re: difference between the calculation by hand and simulatio

thanks for pravin_dwaramwar answer.

I use tsmc BSIM3v3 0.6um model parameters to calculate and simulate,
and Un, Vth, TOX can be found from model
Cox can be get by Cox=εox/Tox
lambda from simulation.
but difference between results are very large than 50% or 100 %.
how to improve calculate???
i need your help , thanks.

 

[xzp]

It dependence on the model you setup, if the model you setup in pspice is the near the same as you calculate, the error will be within 5%.
At less, I did the noise calculation by mathmatica and Pspice simulation, the difference is less than 3%

 

[rfmems]

It really depends on the technology, you are using a 0.6um, which should normally fits well with your simulation if it is a low frequency application.

Added after 36 seconds:

for deepsubmicron CMOS, the square law will not always hold