MOSCAP of 1nF in AMI 0.5um

[raguna]

Hi all,
How to design a MOSCAP of 1nF in in AMI 0.5um process(Cox=2.47fF/um^2). I tried using C=Cox.W.L. But, this was not working fine.

 

[Dominik Przyborowski]

Why You need so large capacitor? If You short D,S and B pins of nmos to ground You should give 1 nF between bulk and gate (with Vgs > Vth) for a transistor with W=L=640um, but it's not practical (better is to use a matrix of 6.4k transistors with W/L=8u/8u).

 

[nitishn5]

A MOSCAP is highly dependant on the voltage across it. You need to ensure that the voltage across it the MOS device is enough to keep it in deep inversion.

Also like Dominik says, it is better to have a multiple units of a smaller device than having one massive device.

 

[raguna]

Thanks Domink and nitishn5,

I used a multiple units of a smaller device and it works fine.

Thanks again.