# How to find Vthreshold and K (or beta) in Pspice/Orcad

Regarding M2n7000 transistor in OrCAD, I want to find its Vthreshold and Beta (or k) by its edit PSpice model. This is what I get : And by Vthresh and Beta (or k ) I mean the parameters of this formula : By the way, regarding This Thread I know the formula for K, but I cannot find all of its parameters in the model I mentioned above. Thanks.

• m0ss - Hi, I am "rolling-back" (reverting) your last edit which removed links to the reference thread and all the images, as the updated version makes no sense without them. Even if you have finished with the question (as signified by you accepting an answer) the question must be left intact, to provide future value for other readers. That is part of the "Stack Exchange philosophy" - to gather questions & their answers for the future. Thanks. – SamGibson Jan 4 at 15:44
• @SamGibson Hi. The issue was that first, I thought the answer it ok. Then I did something else to manually check the answer. But oops, I made a slight mistake and reached another answer where I thought the answer I was given here was false. I edited my question to reflect it. But, I ran the test again and found out I had a mistake and the answer was in fact Ok. As I recall, I just canceled all the new edits where I had claimed the answer is wrong. That's right that all questions answered here must remain intact. I'm sorry for the inconvenience, I did not check that I reverted correctly. Thanks – m0ss Jan 4 at 18:01

## 1 Answer

In the case of a MOS transistor, the threshold voltage, and the transconductance coefficient can be extracted from a spice model.

So, the threshold voltage $$\V_T = V_{TO} = V_{GS(TH)} =1.73V\$$ in case of your model.

And the $$\K\$$ factor is:

$$\K = K_P\frac{W}{L} = 1.073\mu\frac{0.12}{2\mu} = 64.38\textrm{m} \frac{A}{V^2}\$$

The end.

• =+/-25% for Vt (?)and ?% for K – Tony Stewart EE75 Jan 3 at 13:18
• One extra tidbit to know is that this model definition is very strange where it defines both KP directly and its "process" parameters (Uo and Tox) used to calculate it. When there is a conflict like this, SPICE will use the given KP value and ignore calculating it from $\text{KP} = \mu_0 \cdot \frac{\varepsilon_{ox}}{t_{ox}}$. This is important to know since the direct KP value given doesn't match the calculated one. See this answer for more info on this and also how to validate the KP value using simulation results. – Ste Kulov Jan 3 at 18:27