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Simulators >> Circuit Simulators >> plotting reverse saturation current(is) of pnp bjt in spectre,ade
https://designers-guide.org/forum/YaBB.pl?num=1344693364

Message started by yvkrishna on Aug 11^th, 2012, 6:56am

Title: plotting reverse saturation current(is) of pnp bjt in spectre,ade
Post by yvkrishna on Aug 11^th, 2012, 6:56am

Hi,

I am trying to plot the reverse sat current of bjt versus temperature in spectre ade setup of cadence.

'is' is a model parameter for this model bipolar.

doing a dctemp sweep/parametric shows 'is' is constant with temperature (clearly its not so from theory)

any ideas what is missing here?

Thanks,
yvkrishna

Title: Re: plotting reverse saturation current(is) of pnp bjt in spectre,ade
Post by boe on Aug 14^th, 2012, 10:08am

yvkrishna,
model parameter is not evaluated for every sweep point

- B O E

Title: Re: plotting reverse saturation current(is) of pnp bjt in spectre,ade
Post by Geoffrey_Coram on Aug 14^th, 2012, 11:23am

boe -
I think the temperature update of the model parameters *must* be done for every sweep point, but the simulator may or may not make this available for plotting by the user. The simulator may just give back the raw value that it was given (which might involve some complicated equations of subckt parameters, so it's not necessarily a trivial replay of a single number).

-Geoffrey

Title: Re: plotting reverse saturation current(is) of pnp bjt in spectre,ade
Post by boe on Aug 14^th, 2012, 11:37am

Geoffrey_Coram wrote on Aug 14^th, 2012, 11:23am:

Yes, of course. I meant to say: the model parameters in the results are not available for every sweep point...

- B O E

Title: Re: plotting reverse saturation current(is) of pnp bjt in spectre,ade
Post by yvkrishna on Aug 20^th, 2012, 11:12pm

Thanks for your views. I shouldn't go by the name 'is' as its a model parameter.

Is there any other way to plot rev saturation current in a bjt .

Regards,
yvkrishna

Title: Re: plotting reverse saturation current(is) of pnp bjt in spectre,ade
Post by boe on Aug 21^st, 2012, 2:35am

Yvkrishna,
Did you try to use the dc operating point (without sweep) and sweep the temperature with the parametric analysis tool?

- B O E

Title: Re: plotting reverse saturation current(is) of pnp bjt in spectre,ade
Post by yvkrishna on Aug 21^st, 2012, 12:35pm

boe,

Yes I did try with parametric analysis.
Itseems that Model parameter is not at all swept in Spectre simulations.

Thanks,
yvkrishna

Title: Re: plotting reverse saturation current(is) of pnp bjt in spectre,ade
Post by yvkrishna on Aug 26^th, 2012, 5:15am

One way to get it is to write a calculator expr for 'Is' using the well known eqn: VBE = Vt*ln(Ic/Is) .

But it can be inaccurate as this eqn is very preliminary.

Any comments?

Thanks,
yvkrishna