how should I use the W/L value?

[dobb]

in textbook, it's mentioned that there are drawn length and effective length,
which should I use when I instantiate MOSFET symbol in schematic, fill in the W/L blanks and simulate in Spice? should I hand-calculate the effective size then fill in, or just fill in thedrawn length then Spice calculate the effective size internally.

 

[aryajur]

Spice calculates the effective length internally, its based on the models.

 

[Syukri]

Effective length is the result expected after the etching process...

Spice & most simulator had put certain value set, ucan check this value on the default...and it is varied accordingly with the technologied used.

Drawn length...is what we draw on the layout.