How to determine the range of inputs for which cmos devices remain in saturation

[Souljah44]

Hi All,

Given a cmos circuit, is there a setup that can be used to determine the range of inputs for which the devices remain in saturation?
In other words, how do I make sure that my mos devices never leave saturation for a certain input range?

Thanks

 

[Mudasir Mir]

One way is to use the concept of ICMR , & the other procedure is by using the tool (cadence)

Following are the steps for doing that :
1. Make a gedit file with name "saveops.scs" and mention different transistors M1, M2, M3 etc in that file with
the syntax,
SAVE OPPOINT MX;
where X is 1,2,3,4....
2. Save the file.
3. Add the file in model libraries while doing dc simulation
4. Do the parametric analysis
5. Go to dcinfo (i dont remember exactly this but is similar to dcinfo) and click on particular transistor
you will find the range in which your transistor works in saturation..remember you have to keep the parameter variable
corresponding to which you want to see the operation of your transistor

 

[deepsetan]

Hi All,

Given a cmos circuit, is there a setup that can be used to determine the range of inputs for which the devices remain in saturation?
In other words, how do I make sure that my mos devices never leave saturation for a certain input range?

Thanks

Hi,

Basically you can do in two ways (calculation setup & simulation setup). From calculation, you should find the minimum current for your transistor to operate in saturation region. Let say if your minimum current to operate in saturation region is 10uA. So basically, any current >10uA can ensure your transistor operate insaturatiom region. You can find the minimum current from calculation or simulation. Normally, both will gives almost the same value.