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Simulators >> Circuit Simulators >> how to characterize gamma of mosfet
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Message started by avlsi on Jul 21^st, 2012, 10:01am

Title: how to characterize gamma of mosfet
Post by avlsi on Jul 21^st, 2012, 10:01am

Hi all,

We all know that there is factor of gamma in output current noise of the mosfet.
In eldo simulator, the output noise units are v/√HZ. I would like to know how can i get output noise as A/√HZ ?

Thanks in advance

Title: Re: how to characterize gamma of mosfet
Post by Geoffrey_Coram on Jul 23^rd, 2012, 6:35am

Output noise in a spice(-like) simulator is generally computed as the noise voltage at a particular node, hence the units of V/rt Hz.

If you want A/rt Hz, then you need to have a simulator that supports current probes for noise analysis. Check the Eldo manual; I don't know if it does. And you also need a circuit architecture for which the noise current is relevant: if you haven't put on an appropriate load, you circuit won't be supplying current and you won't be able to measure the noise of a non-existent current.

Title: Re: how to characterize gamma of mosfet
Post by avlsi on Jul 23^rd, 2012, 7:04am

Geoffrey_Coram,

I have tried looking for it but could not really find anything.
I am not putting any load on top the mosfet. But I am putting an ideal voltage source to set VDS> VGS-VTH. And then sensing the current using CCVS at drain of mosfet and I anticipate the output of CCVS is actually the current noise of mosfet with gain 1.

Title: Re: how to characterize gamma of mosfet
Post by Geoffrey_Coram on Jul 23^rd, 2012, 8:44am

Yes, that should work. The CCVS does the conversion of A to V, so you can just read the output noise as being in A/rt Hz instead of V/rt Hz.