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how to characterize gamma of mosfet (Read 3455 times)
avlsi
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how to characterize gamma of mosfet
Jul 21st, 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
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Geoffrey_Coram
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Re: how to characterize gamma of mosfet
Reply #1 - Jul 23rd, 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.
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avlsi
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Re: how to characterize gamma of mosfet
Reply #2 - Jul 23rd, 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.

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Geoffrey_Coram
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Re: how to characterize gamma of mosfet
Reply #3 - Jul 23rd, 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.
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