337see733
Community Member
![* *](https://designers-guide.org/forum/Templates/Forum/default/stargold.gif) ![* *](https://designers-guide.org/forum/Templates/Forum/default/stargold.gif)
Offline
Posts: 39
Singapore
|
Main reason why most ppl represent the parasitics with one operating point:
Limitation in the existing compact model. The existing compact model is not developed with RF applications in mind, but rather for DC and low frequency AC applications. To really incorporate the RF effects, both "intrinsic" and "extrinsic" are to be modeled to change with respect to frequency. However, this is likely to lead to very complicated compact model. Therefore, as engineer who usually want to solve the problem, short-cut route is taken. It is assumed that the parasitics are independent of bias voltages (of course it is unlikely, you can think some of the lumped elements are actually voltage dependence resistance, capacitance and inductance, but you may not know how it is to relates to all the 4-terminals..!).
I assumed you don't have the liberty to change the intrinsic model. However, do check the capacitances for the intrinsic device. It is usually difficult to model the short channel capacitance, as usually the shortest lengths are used for a technology. If you still want to fit the S-parameters, what you can do is to use the external elements to either enhance/compensate the accuracy. In anyway, it is a challenging job..haha
GOOD LUCK!
|