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How to know a mos capacitor's value?Thanks.

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holddreams

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mos cap

When the drain and source of a NMOS connected using as a capacitor(for example w/l=10u/1u),how to know the equivalent capacitor value?

Thanks.
 

capa mos value

1> the estimate value=W*L*(square capacitance), you can find the square capacitance (ff/um^2) in process file from process supplier.

2> also, you can simulate the MOSCAP and an idear cap in same condition by Hspice, compare their I/V curve, the same I/V curve means the same capacitor value.
 

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    holddreams

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how to know capacitor value

in hspice add a line
.options captab
then check the *.lis file , hspice will report capacitance of all nodes.
 
nmos capacitor

you can do dc simulation. The DC operation point will give the capacitor value
 

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    holddreams

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mos capacitor

You can do transient simulation,then calculate the capacitor value.
 

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    holddreams

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mos capacitor simulation

yep, perform a dc analysis in cadence and look at the op point of the transistor.
 

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    holddreams

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moscap capacitance

I think that you must do transient simulation If you want to know the MOS capacitor variation with Vgs variation.
 

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    holddreams

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hspice moscap

There are many methods.
I think calculating by hands is the best way.
 

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    holddreams

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hspice lx22 capacitance

Thanks a lot for your replies.

Would you please post the Hspice or spectre simulation file which include the dc and transient analysis here?
 

mos capacitor drain source

You can obtain the equivelent capacitance of MOSCAP by HSPICE transient simulation. caculate the total charge (Q) stored in the CAP in fixed voltage range (Vr), then the C=Q/Vr .
 

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    holddreams

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mos value

U can simply do an AC simulation with a voltage source connected in series with the mos cap, by setting the AC voltage to 1 and w=1 ,u can get the value of the capacitance as it is simply the current coming out of the ac source.
i=V/Zc
=jVwc ==> c=i/wV (for V=1, w=1) ==> c=i
 

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    holddreams

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hspice mosfet cagte capacatance

hi holddreams,
Using a ideal current charge the MOS cap,then using calculating function on cadence artist, you can get the C=I/(dv/dt).
 

pmos capacitor in cadence

I want to know how to show a "helped me " button?:D
 

nmos capacitance

The capacitor values depend on the voltage applied to the Gate of the transistor which decides its region.
Ex: Take Vgs is negative then it is in accumulation region and the capacitance is Cox now on if u increased Vgs and the depletion region is formed in that case the capacitance will be Cox+Cdepletion again u increased Vgs till the inversion takes place below the oxide and that time the capacitance becomes Cox. This are the three regions of operation called as
1.Accumulation,2. Weak Inversion,3.Strong Inversion and I think this might help u to get the capacitance of the NMOS. If anything else needed let me know.
 

capacitor using mos

Hi

you can plot the cap. by
.print lx18(m)

spice said:
LX18(m) = CGS+CGD+CGB
LX19(m) = LX32(m) = -CGD
LX20(m) = -CGS
LX21(m) = -CGB
LX22(m) = -CDB
LX23(m) = -CSB
LX33(m) = CGD+CDB+CDS
LX34(m) = -CDS

you can check it in the .lis file
.option captab

Stoned
 

mos capacitor ff/um

the easiest way is characterize yourself!
 

simulation of mos capacitor

Hi

Does Lx18(m) work in hspice?
 

mos capacitance simulator

There is a demo directory that comes with HSPICE, which contains examples using LX18 to charactrize MOS caps.
 

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