Calculate the intrinsic elements of FET using ADS, help!

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GameKing

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Hi everyone,

I have tried to calculate the intrinsic parameters (Cgs, Cgd, Cds, Ri, gm, gd and Tau) which are functions of the biasing conditions by ADS tool but I cannot simulate it.

How do I measure them in ADS tool?
 

Thank pancho_hideboo,

However I want to measure the intrinsic parameters: Cgs, Cgd, Cds, Ri, gm, gd and Tau which are as functions of source-to-gate voltage.
 

GameKing said:
However I want to measure the intrinsic parameters: Cgs, Cgd, Cds, Ri, gm, gd and Tau which are as functions of source-to-gate voltage.
Click to expand...
You can't measure these directly.

You have to determine these by fitting with varying bias points.

Some parameters such as gm and gd, you can measure directly.
See
 

I want to determine the gm,gm',gm'' in ADS
how can I calculate them?
 

laperla said:
I want to determine the gm,gm',gm'' in ADS
how can I calculate them?
Click to expand...

By definition...
\[\displaystyle Gm=\frac{\partial Ids}{\partial Vgs }\]

in ADS, connect a I_Probe.i element and use diff command sequentially and find your \[GmGm'Gm''\]
I mean
\[ Gm=\frac{\partial Ic}{\partial Vbe}\]
\[ Gm'=diff(Gm)\]
\[Gm''=diff(Gm')\]

etc..
 
Last edited:
thanks for answer
I did it but when I sweep the Vgs and want to get gm vs. vgs but ADS gives me gm v. freq
how can I dram curve gm vs. Vgs?
 

laperla said:
thanks for answer
I did it but when I sweep the Vgs and want to get gm vs. vgs but ADS gives me gm v. freq
how can I dram curve gm vs. Vgs?
Click to expand...

Do Swept DC simulation..Put your Vgs voltage as a variable in DC Simulation block and then obtain Ids versus Vgs...
Then differentiate it..
 
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