MOSFET Parameters

[EN0]

I recently watched an MIT lecture on MOSFETs and have accumulated a few questions. Here, you will find the notes on the particular lecture. The professor says that a MOSFET will have the following given parameters:

[LATEX]K[/LATEX]

[LATEX]V_T[/LATEX]

I’m wondering how I can find those values on a MOSFET datasheet? I have no idea what K is and I’m guessing that Vt is Vgs? Let’s use this datasheet, for instance.

I’d appreciate any help; I’m trying to create my own MOSFET amplifier.

Austin

 

[ericgibbs]

I recently watched an MIT lecture on MOSFETs and have accumulated a few questions. Here, you will find the notes on the particular lecture. The professor says that a MOSFET will have the following given parameters:

[LATEX]K[/LATEX]

[LATEX]V_T[/LATEX]

I’m wondering how I can find those values on a MOSFET datasheet? I have no idea what K is and I’m guessing that Vt is Vgs? Let’s use this datasheet, for instance.

I’d appreciate any help; I’m trying to create my own MOSFET amplifier.

Austin

hi ENO,
If you use LTspice unzip this zipped file to get lib_test.asc and mymosfets.lib
[downloaded from the Yahoo LTS user group].

You can modify the N and P mos parameters by using a text editor to open then mymosfets.lib.

EDIT:
Threshold voltage - Wikipedia, the free encyclopedia

About VT(threshold voltage) of MOS

 

[EN0]

Hi Eric,

What is the text editor under in the files?

EDIT:

Is this right for the text editor? What exactly do you want me to do?

.model N4007 NMOS(Level=1 VTO=1.9 KP=27u W=100u L=2u Lambda=0.025 Gamma=0.5)
.model P4007 PMOS(Level=1 VTO=1.9 KP=27u W=100u L=2u Lambda=0.025 Gamma=0.5)

 

[ericgibbs]

Hi Eric,

What is the text editor under in the files?

I dont quite follow your question, do you mean which text editor type.... its just a plain text editor,,, like notepad.

I have added to that post...

 

[EN0]

Sorry, I think I opened it ok. See my above edited post.

 

[ericgibbs]

Sorry, I think I opened it ok. See my above edited post.

Hi,
When using the LTS simulator, you edit the parameters in that .lib in accordance with the MOSFET you are wishing to simulate.
Many MOSFET manufacturers publish these parameters.

 

[EN0]

I didn't really want to simulate a MOSFET, but thanks.

The PDF files you provided were informative; I believe I have the correct parameters identified within the context of the datasheet. I have a couple MPF102's I wanted to mess around with, so that should be fun I think. I wanted to confirm my assumption of where the parameters are on the datasheet:

"K" = Forward Transconductance (2,000µSto 7,000µS)
Vt = Threshold Voltage, referred to as Vgs in datasheet (-0.5V to -7.5V)

Does all of that seem correct?

 

[EN0]

Here's my equation I came up with:

[LATEX]V_O = V_S - \frac{K}{2} (V_{IN} - V_{TH})^2 R_L[/LATEX]

[LATEX]V_O = 15 - \frac{5000E-6}{2} [V_{IN} - (-0.5)]^2 1E3[/LATEX]

The datasheet only provided minimum and maximum values, so I selected arbitrary values in between. I'm going to find the valid input and output operating ranges and then test it on a scope.

I'll keep you posted!