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Cadence UMC18 process which MOS transistor for RF frequency

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bestvlsi

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Hi All,

I am making a VCO which should oscillate at a frequency of 2.5GHz . I ve been using N_18_MM and N_LV_18_MM till now. But there are few RF transistors also present in the UMC_18_CMOS library . Is there a need to go for those since my frequency of operation is high. Or will it do if I continue with the above mentioned _MM transistors?

Moreover can someone explain what is the speciality of these _RF transistors.

Regards,
 

Since the frequency of operation is at the order of GHz you should definitely go for the RF transistors.RF transistors consist of a more complete and accurate model for the various electrical phenomena that are present at high frequencies.Thus,you will have a more robust and confident simulation that you can be based on during your design phase.Additionally,you will have less uncertainty for surprises after the layout and during post-layout simulations (given that you will do a careful job during layout).
 
Agree with jimito13 : MM are the std. MixedMode transistors, well characterized for LF analog applications, whereas the RF transistors are specially characterized for RF frequency applications, s. e.g. this header of a 180nm RF SPICE model file: View attachment rf018_header.txt
 
Thanks jimito and erikl .. I am using the RF transistors now and indeed they are better as they are optimized for the number of fingers and the finger widths which are quite critical in RF applications. Since Ive seen in the layout that the finger width is kept minimal to reduce poly resistance and also the width range which can be used has been restricted to a particular range.
 

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