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Analog CMOS parameters calculation

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lqy

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cmos parameters

Dear all,
When we desgin analog CMOS circuit by hand calculations, we need to know gm, rds, Cdb, Cgs and Cgd, could some experts tell me how to get the above parameters from model file.
The model file are very complicated, I don't know how to calculate it.

layout analog cmos

A simple method,you could do dc or op simulation to get the dc operating points, then see the parameter including all you said. Then you can calculate the gain,bw,pm and so on.
Another difficult method,you can read the model file and get the basic parameter,like mobility,tox,vth and the temparature factor to calculnate the parameter you need.

Parameter description of the model file could be found in the documents provided by foundry.

cmos cgd

you can find the mobility(u) from model file by the parameter (u0)
and threshold voltage by the parameter VTH.
also you can calculate the Cox by the parameter TOX in the model file following the equation
Cox=3.45fF*(100e-10)/TOX.
Generally, you can calculate the gm as the equations textbook.

Mostly the Cgs can calculate following which region it works in. For example,in saturation region, the Cgs=2*W*L*Cox/3. For more information, you can refer to the Razavi's or Gray's textbook. Cgs , Cgd and Cdb are discussed in detail.

Last, in my opinion, the rds most is obtained from the simulation, not from the manual calculation.

explain each parameter in mos model file

lqy said:
When we desgin analog CMOS circuit by hand calculations, we need to know gm, rds, Cdb, Cgs and Cgd, could some experts tell me how to get the above parameters from model file.

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cmos tox calculate

If you can accept 50%-100% error in your hand calculation wrt the simulation results, then go ahead and do all this.
Otherwise, for better results search info about gm/Id design methodology.

cmos calculations

you can perform DC simulation and find the above parameters from Results Brower which contains those in DCopInfo-info.

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