erichih
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I happen to study something about NQS recently. Hope this will help.
NQS effect happens when input frequency is pretty high at the order of transit frequency. A resistor, which is series connected with the Cgs, is used to model the time delay between the stimulus at the gate and the response at the channel by Elmore, and the resistance value can be expressed by 1/(5*gm). Then later on, Prof. Chenming Hu published some papers, saying that the NQS effect could be best modeled by an external resistor, whose value is extracted from the y parameters. So even there are no ELM or NQSMOD parameters in your model, which is QS model. You still can use an external resistor to simulate the NQS effect. Moreover, the inclusion of an external resistor at the gate termal can give us another benefit, i.e. the gate-current noise, which is correlated to MOSFET thermal noise, through Cgs capacitive-coupling. (Why? Please go to see Prof. Thomas Lee's paper about 1.5GHz LNA.) I believe that this kind of noise is not included in the model, neither.
---Eric
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