How do we define V_DS,sat for short-channel MOSFETs? On page 297 we see

Eq. 9.54 as V_ov = V_GS - V_THN is not = V_DS,sat. I don't understand this?

As seen in Fig. 6.11 V_DS,sat is simply the drain to source voltage on

the border between the saturation and triode regions in either long or

short channel devices (note that no deep thought is required.) In long-

channel devices V_DS,sat happens to be the same as the overdrive voltage.

In short-channel devices it's not (as seen in Eq. 9.54). 

Q: How do I determine V_DS,sat in a nanometer process though?

Ans: You look at the I_D-V_DS curves, Fig. 9.31 for example. This is why we

use the plots for design in nanometer processes and not equations!

Note don't spend time looking for a simple equation (like V_DS,sat = V_GS - V_THN).

For example, V_THN is not a constant but rather a function of V_DS, V_SB, etc.

Another question: Are the short channel effects present for only very small L

transistors? If I choose L = 2 um in 180 nm technology, do the short-channel

effects still exist?

See the previous email response (number 7).

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