Kn value of a specific transistor given spec sheet

extremepilot

Hi,
Working on a project, I am told to find the K,n value of a specific transistor (2n7000), given the spec. sheet. I know K,n can be found from the formula:

I,d = K,n * (V,gs - V,tn)^2

I'm close, from the spec sheet, I can use a V,gs value and a corresponding I,d value, however not sure what value to use for V,tn to complete the equation and solve for K,n. Any help?

Thanks for your time

waht

That's a thermal voltage that depends on temperature. It's approximately 26 mV at room temperature.

extremepilot

That is V,t which is 26mV like you said but what I am looking for is K,n which is in units if mA/V
I believe

waht

Look up a spice model for the transistor. It should be there. And the units should be A/V^2

extremepilot

Thanks, tried this - I placed the 2n7000 in the circuit and clicked "Edit Properties" on it but I can't find ANYTHING in the property editor

Any help is appreciated

waht

Simple google results:

Code:

*ZETEX  2N7000  Spice Mosfet Subcircuit  Nodes D G S  Last revision 11/91
*ZETEX  60V 200mA pkg:TO-92
.SUBCKT X2N7000 3 4 5
M1 3 2 5 5 MOD1 L=1 W=1
RG 4 2 343
RL 3 5 6E6
D1 5 3 DIODE1
.MODEL MOD1 NMOS VTO=2.474 RS=1.68 RD=0.0 IS=1E-15 KP=0.296
+CGSO=23.5P CGDO=4.5P CBD=53.5P PB=1 LAMBDA=267E-6
.MODEL DIODE1 D IS=1.254E-13 N=1.0207 RS=0.222
.ENDS X2N7000

If you are using LTSpice, go to the LTSpice directory and find folder lib/cmp and look under mosfets.

extremepilot

Thanks. I have no idea what LTspice is, but doesn't look like it's installed on my school's computers. Part of the assignment is to enter these characteristics (K,n V,t W, L etc ) into one of the regular Mosfet Ntype transistor models so it acts as a 2n7000, rather than using the 2n7000 model itself... Waht, is there any chance you could tell me how I would do that? I dont see how to do it at all.
Thanks

EDIT: Seems like I need to use the PSpice model editor, and type in the values of the 2n7000. I'll try and figure the rest out.
Thanks a lot

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waht	That's a thermal voltage that depends on temperature. It's approximately 26 mV at room temperature.

extremepilot	That is V,t which is 26mV like you said but what I am looking for is K,n which is in units if mA/V I believe

waht	Kn value of a specific transistor given spec sheet Look up a spice model for the transistor. It should be there. And the units should be A/V^2