Does anyone have any good and specific documentation on mos varactors such as accumulation mode varactors and inversion mode varactors?
I am trying to compare the characteristics of using an active capacitor to a passive capacitor for creating a loop filter in a pll. Any suggestions would be greatly appreciated.
SmirC@Stanford had published some papers on the accumulation mode varactor since 1998. You can google it by the key words: mos varactor at stanford website.
my suggestion is based on only experience
accumulation mode is;
good for taking capacitance ratio uver 3
good for 1Volt operation
bad--capacitance absolute value depends on concentration of inpurity
bad--well or sub registivity and capacitance stringly affects tanDELTA
inversion mode is ;
good for gtting spice model
bad--small capacitance ratio
i have used accumulation (pch) \\was good for repeatability
Take a look at the attached document. It has some good information in varactors used at medium and very high frequencies. i.e. 25.9 GHz.
Some layouts are also available.