how to obtain small signal paramter values using hspice

Dec 06, 2006 0 Replies

Hi,



Given a circuit with nmos and pmos devices, I am trying to find the ac small signal paramter values (gm,gmb,cgs...) using star hspice.



I perform a .op analysis which gives me gm, gmb etc. My question is about the intrinsic capacitor values.



.op analysis gives cgtot, cbtot, cstot, cdtot, cgd, cgs.



I found that for myer capacitance model cdtot = cgd+cdb cgtot = cgs+cgd+cgb cstot = cgs+csb cbtot = cgb+csb+cdb



I am using hspice level 49 for my simulation. In that case, how to obtain Cbs, Cdb, Cgb from the tot values. Do the above equations hold?



My understanding in this regards is poor and any help is welcome.



Regards, Almitra.



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