[SOLVED] Regarding moscap value

[akash1308]

Hello all,

I am using cadence umc 180nm technology. I want to replace MIMCAP from my circuit because of huge area. currently I am simulating with MOSCAP with the same size but in simulation capacitor value giving very small (Instead of 500pF its showing 12pF).Voltage applied range is from 300 mV to 500mV.
Please suggest me how to use and if possible some different technique.

regards
Akash

 

[nitishn5]

A MOSCAP requires a minimum voltage across it to give the maximum capacitance.
It gives the maximum capacitance when it is in strong Inversion i.e. the Vgs > Vth when the channel is full formed.

Check Razavi's "Design of Analog CMOS Integrated Circuits" page 39.

Btw, MIMCAPs ca be placed over active devices and therefore might not be as much are as you think. You could place your entire circuit under a big MIMCAP and not use any extra area.