Changing Vth (Threshold voltage) in Cadence

[msdarvishi]

Dear all,

I want to change the threshold voltage (Vth) of a MOSFET in Cadence and do a parametric solution to find out its effect on my circuit. Any body can help me how can change Vth in Cadence? The available technology is TSMC 0.18µm.

Thanks,

 

[dick_freebird]

The easiest approach is simply to put a series voltage source
between the FET gate and its driving source, with (say) v=dVTN
to make the (effective) VT variable from within ADE.

Otherwise you need to drill down into the models/spectre dir
and edit the pertinent FET model card, making its VT0 (or
whatever your particular model uses) a Spectre variable if
it's presently a fixed item, or add an "adder" (like if it's
VT0=avtn+dvtn(), make it VT0=avtn+dvtn()+myvtn and
add myvtn to your variables list.

If the PDK is outside your authority to edit, then make a
local copy and have at it, and link it instead of the default.

Most modern processes probably offer you either corners
or MC access to device params, and you may already
have those "hooks" if you inquire of the foundry modeling
people or your own CAD group.

 

[msdarvishi]

The easiest approach is simply to put a series voltage source
between the FET gate and its driving source, with (say) v=dVTN
to make the (effective) VT variable from within ADE.

Otherwise you need to drill down into the models/spectre dir
and edit the pertinent FET model card, making its VT0 (or
whatever your particular model uses) a Spectre variable if
it's presently a fixed item, or add an "adder" (like if it's
VT0=avtn+dvtn(), make it VT0=avtn+dvtn()+myvtn and
add myvtn to your variables list.

If the PDK is outside your authority to edit, then make a
local copy and have at it, and link it instead of the default.

Most modern processes probably offer you either corners
or MC access to device params, and you may already
have those "hooks" if you inquire of the foundry modeling
people or your own CAD group.

Unfortunately, it does not work ! because I cannot change the model file nor able to make a copy of it ! Is there any other approach??

Thanks

 

[dick_freebird]

That's an awful lot of helplessness for a designer. And
the first suggestion can be done at schematic level. Be
sure you know what's impossible, and what's merely not
obvious / convenient.