I have a basic question. How do you desice dc operating point?
I have been decided operating point small overdrive voltage. Is it OK? And Vds is decied Vds=vdsat+0.1(or 0.2)V.
Please tell me your method to decide dc operating point. Thanks~
what is the circuit for which you want to decide a DC operating point....
assuming that you are talking about a amplifier the selection of the DC operating point or Q point should be in the middle of the loadline so that the circuit is stable through signal swing.... if you decide on Vds=Vdsat+0.1V or 0.2V it might not be the right point so you better find the DC point graphically....
if you have the datasheet of the MOSFET you are using then take the desired values of x(Vgs) and y(Id)... now mark your required value of Vgs when Id=0 and required value of Id when Vgs=0.... now join these two points and you will get a line called the load line... take the midpoint of this line as your operating point and bias accordingly....
the DC operating point should be in your input voltage range. and it should maximize the input voltage swing, just like what is said above, it should be best at the middle of the input voltage range.