Does the length of mos can exceed the upper limit in PDK?

[xianweng]

Hi ,all
Does the length of mos can exceed the upper limit in PDK? In my pdk and technology file ,the max length is 10u.Does the length of mos can exceed it just as a capacitance for filter purpose ?
thanks anyhelp in advance

 

[dick_freebird]

Very long MOS make poor capacitors because of the channel
resistance. Better to make wide, up to the point that poly
resistance becomes more than channel resistance, and use
multiple fingers if you want more improvement.

PDK limits of this sort are more likely to represent the limits
of modeling effort, than any physical limit. Especially in a
"digital" flow, the idea that anyone would use L>10um is
pretty remote. But of course people keep trying to use
cheap digital flows to do analog stuff.

 

[xianweng]

Thank you very much
I see

 

[AdvaRes]

To avoid the PDK limits and to have a good moscap, fingered transistors is a nice choice.