What is the difference b/w VOD and VDSAT?

[bobxing]

vdsat

In hspice2005.9 and later, for a simple mos transistor simulation, the op has the
calculation of vod=.. and vdsat=.. they might be considerably different.

Anyone can tell their difference?

Thanks in advance.

Bobxing

 

[bsrivastava]

what is vdsat

Difference of Vds and Vdsat is Vod. Vds-Vdsat = Vod
thanks
-Bharat

 

[bobxing]

hspice vod

You give me a good clue. Thanks
I studied the simulated list file.

Vgs-vth=vod,

But Vds-vdsat <> Vod!
so how come? the vdsat?

 

[Material]

vdsat

For long channel device
Vod equal to Vdsat

For short channel device
There existed a lot of second order effects
So Vdsat is not simply equal to Vod

If you want to find out how the hspcie get the vdsat you can refer to the hspice manual, model level.


While in hand calculte we use vod(vgs - vth) instead of Vdsat to simplified the calculation process.

 

[mpig09]

vdsat and vod

Dear all:

Please reference this: http://www.ece.uci.edu/docs/hspice/hspice_2001_2-162.html

If MOS is linear region, vod will closed to vdsat, but when MOS in sat region,
vod will bigger than vdsat.

If you use vod to design you circuit, you will get more margin to ensure the mos in sat region when circuit in different corners and temp.


mpig