Knee Voltage : MOSFET

[prasadpiyer]

hi, 

I am a newbie at labview. 

I wanted to know how to find the knee voltage from the characteristic curve of a mosfet transistor. ( I am working with experimental data which are not IDEAL )

My inputs are 2 arrays of Voltage and Current

My approach : 

I was hoping to curve fit the initial part of the values onto a quadratic curve : since my input is an array : i will start a loop(counter i ) from 1 - i - n ( size of array ) and fit the values from 1- i in a quadratic curve and find the value of i which has the least value of error.  I used the standard curve fitting tool to do this and generate the mean squared error from that but i am getting a problem from of converting the 2 arrays ( current and voltage ) into one signal which would serve as the input to the curve fitting tool in labview( PLEASE HELP HERE )

I also wanted to know

1) is my approach correct

2) is there any alternative approach 

3) my ultimate aim is to find the mobility factor of the mosfet using the Saturation voltage i generate from this approach (Saturation voltage i am assuming is approx equal to knee voltage )

Kindly reply ASAP and for any further information : prasadpiyer@gmail.com

Regards

Prasad P Iyer

IIT Kanpur

India

[GerdW]

Hi Prasad,

we will answer here in the forum and we will ask questions here in the forum. No need for your private email adress - atleast you like SPAM...

To judge your approach you should attach the VI. What is "the curve fitting tool" you're talking about?

[prasadpiyer]

hi,

oh ok i am attaching the VI but it has some errors. i hope my approach will be clear.

and the possibility of spamming in such an academic  forum didnt cross my mind at that time :  thanks for the tip 🙂

the questions which i raised in the previous ( orginal ) post remains

Regards 

Prasad

[GerdW]

Hi Prasad,

I removed those ExpressVIs, the VI should still do the same...

Could you attach some sample data?

[prasadpiyer]

hi ,

Thanks for your post but since its in labview 9 ... i couldnt access it with my labview version 8.5. it is showing an error .. could u please modify ur vi accordingly

Thank you

The sample data is attached here . the Vg = -2v for the data

Regards

Prasad

[GerdW]

Here it is in LV8.5...

[prasadpiyer]

Hi,

Did you test it out with the data i send, everytime its giving the value closest to zero.

I really need to know if my approach is correct and the correct way to find the knee voltage given such an input

Regards

Prasad

[GerdW]

Hi Prasad,

please make a picture and show which point exactly you want to find! Never worked with MOSFETs...