# How to plot MOSCAP C-V curve using Cadence Spectre in ADE?

1. ## How to plot MOSCAP C-V curve using Cadence Spectre in ADE?

How to plot a MOSCAP capacitance versus Vg using Cadence ADE and Spectre? •

2. ## Re: How to plot MOSCAP C-V curve using Cadence Spectre in AD

for moscap, C-V fullfill the formular: V=I*Z=I/(jwc) , so |C|=|I/(w*V)|
if V=1,w=1 then C=I

Insert a dc voltage source in the gate of moscap, set the "ac amplitude" to 1 and dc voltage to "Vin". Do ac simulation and sweep the parameter of Vin from -2V to 2V at frequency "1". Plot ac current "I" of the terminal "G" and the C will be the same as I.

Lorry

2 members found this post helpful. •

3. ## Re: How to plot MOSCAP C-V curve using Cadence Spectre in AD Originally Posted by sharpsheep
Insert a dc voltage source in the gate of moscap, set the "ac amplitude" to 1 and dc voltage to "Vin". Do ac simulation and sweep the parameter of Vin from -2V to 2V at frequency "1".
Lorry
Hi,

Just to be sure.
What do you mean by "at frequency "1"" ? The real frequency f or w ?
I think you mean w. Is it that ?

Actually, w=2×Π×f, if I wanna have w=1 I have to setup f=0.159 Hz.

What about amplitude of the ac signal. Why set it to 1 ?
Why not Vdd ?

Thanks in advance for you reply.

Advares. •

4. ## How to plot MOSCAP C-V curve using Cadence Spectre in ADE?

Or you could step V in a DC OP simulation, Parametric
Analysis, and just plot op(cgg). If you're not set on directly
emulating the measurement setup.

If you set the measurement signal large then your C will be
changing all the time, and since it's nonlinear you can't just
go and average it. Though in AC analysis it's all bogus, if
you ran a transient you'd see C varying across the cycle at
1V amplitude (especially if you're swinging across inversion
threshold). Setting input amplitude to 1 for AC is just a simple
default and often makes the output amplitude be a useful
datum directly (like, if input=1 then output amplitude also
= gain).

I'd be applying transient stimulus amplitude that is maybe 1%
of full span, if I wanted 1% kind of accuracy where things are
changing a lot.

1 members found this post helpful. 5. ## How to plot MOSCAP C-V curve using Cadence Spectre in ADE?

You could charge it with a constant current in a transient analysis and plot the slope.

Keith --[[ ]]--