MOS varactor question ..

[super]

mos varactor simulation in ads

Dear all :
I use NMOS do a MOS varactor , in simulation I tied D/S/B together
and do a one terminal and gate is another terminal,
this method is correct ??

Thanks ..

 

[pfd001]

it is impossible for you to connect your bulk to D and S if you didn't have a seperate well for nmos. you can connect the bulk to ground and use the D and S as one terminal and gate as another terminal.

 

[super]

I use 0.18um process have provide MOS varactor model , but because model size is too large so I want to use NMOS to model MOS varactor.

So can I connect bulk to D and S as one terminal and gate is another terminal for "simulation" do a MOS varactor ??

Thanks ....

 

[safwatonline]

as u said it needs a model "i guess"

 

[super]

Sorry , I'm not clearly understand your answer .
It means I can use this method for simulation , right ?

thanks .

 

[safwatonline]

hi,
as u mentioned the varactor has its own model for simulation and hence if u use the NMOS model i think it wont be accurate

 

[Shohdy]

Hi,

Actually the bulk of the NMOS will be connected to the whole bulk of the substrate (which is grounded)...unless as mentioned above the NMOS is in a seperate well.
So if one terminal of the cap you are using will be always connected to ground. If that's ok with you the go on. If not, you can try using a PMOS instead, as PMOS can be easly put in a seperate N-well.

Hope that helps,

Regards,
Shohdy