test setup for measuring cgs,cgd etc in AC simulation.

[yvk]

Hi all,

I would like to measure the device caps for a mosfet in AC simulation.

(ofcourse DCOP directly gives it, idea is to apply this setup for a new composite device)

I have tried using 'sp1tswitch' in cadence spectre but unable the get the exact split of cgs,cgd,cgb from the total node cap cgg.

ex: apply Ac=1 at gate of a mosfet and see the imaginary part of current flowing through the source which is nothing but the cap loading at the port.

similarly is it possible to get the junction caps only in simulation?

Thanks,
yvk.

 

[Andrew Beckett]

On 11/03/12 11:34, yvk wrote:

Hi all,

I would like to measure the device caps for a mosfet in AC simulation.

(ofcourse DCOP directly gives it, idea is to apply this setup for a new composite device)

I have tried using 'sp1tswitch' in cadence spectre but unable the get the exact split of cgs,cgd,cgb from the total node cap cgg.

ex: apply Ac=1 at gate of a mosfet and see the imaginary part of current flowing through the source which is nothing but the cap loading at the port.

similarly is it possible to get the junction caps only in simulation?

Thanks,
yvk.

I don't really understand the question.

Andrew.

 

[yvk]

Andrew,

When we want to measure the cap loading across any port or 2 terminals, simple experiment is to apply an AC voltage across it and finding the imaginary part of the current would be sufficient to extract the cap value.
I would like to do a similar experiment to find the device caps of mosfet across each 2 terminals.(without disturbing the DC biasing).

Thanks,
Vamshi


On Tuesday, November 20, 2012 9:11:00 PM UTC+5:30, Andrew Beckett wrote:

On 11/03/12 11:34, yvk wrote:

Hi all,



I would like to measure the device caps for a mosfet in AC simulation.



(ofcourse DCOP directly gives it, idea is to apply this setup for a new composite device)



I have tried using 'sp1tswitch' in cadence spectre but unable the get the exact split of cgs,cgd,cgb from the total node cap cgg.



ex: apply Ac=1 at gate of a mosfet and see the imaginary part of current flowing through the source which is nothing but the cap loading at the port.



similarly is it possible to get the junction caps only in simulation?



Thanks,

yvk.





I don't really understand the question.



Andrew.

 

[Andrew Beckett]

On 11/23/12 09:22, yvk wrote:

Andrew,

When we want to measure the cap loading across any port or 2
terminals, simple experiment is to apply an AC voltage across it and

finding the imaginary part of the current would be sufficient to extract
the cap value.

I would like to do a similar experiment to find the device caps of
mosfet across each 2 terminals.(without disturbing the DC biasing).

Thanks,
Vamshi

OK, but I don't think it's possible to isolate these internal capacitances.

Andrew.