Technology Current dependency on Gate-Length
Dear @erikl,
Let me take the advantage of this post to make a question about something that I have forgotten, regarding the
technology current, I
0, and that is linked with the inversion coefficient, IC.
The way Binkley derive this current, which can be seen in his book, is model independent?
My question:
According to Binkley his technology current is fixed, in this case around 0.64uA. How the simulation that we are doing gives different values of I0 for each W=L?
Your answer:
If you had read/studied the Binkley - or any other Analog Circuit Design - book thoroughly, you'd know the answer: short channel effects as carrier velocity saturation (mobility reduction due to the longitudinal field), CLM and VFMR throttle (pinch, reduce) the drain current most at Lmin, and less and less at longer channel lengths. That's why you get a low I0 value at Lmin and some higher, but more and more saturating I0 values for longer channel lengths.
erikl, I would like to clarify something. I had to read two or three times you answer and my question :lol:
I know all the things that you mentioned on your answer. But what I meant to ask is the following:
If you look at Binkley results and informations in the book, starting for example on page 43 (table 3.2), you can see that his technology current is 0.64uA and it was calculated based on the I
0 expression and his technology parameters.
As you can see, this current doesn't depend on the W/L ratio and he uses this I
0 current throughout his examples, as you can see in some tables or plots.
One example of this is on page 63, figure 3.7. This plot exercise is using the I
0 of 0.64uA and it has in its x-axis the IC which depends as well on I
0.
What is confusing me is the fact that when we simulate, we are using different values of W, with W/L=1. This gives different values of currents.
Now when Binkley says for a certain plot or whatever that the technology current is 0.64uA, W/L=1 etc, etc, how do we know which value of W, and consequently the value of L, he used? Do you understand what I mean? Please, if you didn't understand tell me to try another way.
Please, I am looking forward to hear from you. I will be waiting for you answer as this piece of information is very important to me.
Thank you for you time and availability.
Regards.