Good morning i'm trying to get the frequency response of a single-ended CS amp (BW 10GHz) and when i try enter the prompt of "plot db()" in ngspice it shows this error argument out of range for divide/db. any help ?

Try using

plot db(abs(out)+1f)

Thank you Luis for answer what do you mean without db ?

Vdb only works with non zero values, I think

i get it thank you