Hi all,
so it seems it's not possible...
I just want to add that in my opinion it's *not* a realistic waveform. As
Andrew said, such an
exponential wave makes abrupt transitions, which does not happen in
practice.
As better solutions, I would suggest the following :
- use a vpulse source with edgetype set to 'halfsine', this option is
relatively new I believe but
it gives pretty nice wave shape.
- make s subcircuit with a vpulse source driving an RC circuit, then use a
vcvs source with gain=1
to replicate the resulting wave at the input of your circuit. This can
give nice shape too.
- use a real circuit to produce a real input waveform (say, a CMOS
inverter or whatever's close
enough to what will really produce the wave in the real circuit)
You'll probably find that it doesn't make much of a difference on the
results anyway, which possibly
explains why nobody's asked for such a feature before...
Good luck,
Stéphane
Andrew Beckett wrote:
> AG wrote, on 09/02/08 08:19:
>> On Sep 1, 11:54 pm, Riad KACED <riad.ka...@[EMAIL PROTECTED]
> wrote:
>>> Hi,
>>>
>>> I honestly don't know how to define a periodicity for the 'analogLib/
>>> vexp' voltage source. I'm just wondering whether it is possible. I
>>> went through the Analog Library Reference Guide do***ent but it was
>>> not that much helpful for this case. Hope some experts will set us
>>> straight on this.
>>>
>>> Meanwhile, I'm seeing 2 potential solutions off the top of my head :
>>>
>>> 1. Write a Verilog-A source. I think I've seen some examples on the
>>> Accelera/Designer's Guide web sites, can't remember :-(
>>> 2. you can write a piece of skill/perl/C/Matlab... to generate a time-
>>> limited waveform into a file that you could use to feed the vpwlf
>>> source.
>>>
>>> Cheers,
>>> Riad.
>>
>>
>> Riad,
>> Thanks for your suggestions.
>> Yeah, the do***entation doesn't help much. Seems like its not
>> possible. But, I don't understand why not.
>> I'll check into #1.
>> #2 did occur to me but I'll try it as a last resort :-(.
>> Thanks once again.
>>
>> Regards,
>> Anand
>>
>
> I don't see "exp" sources being used very often, in practice. I checked,
> and it seems that spectre's vsource does not sup****t "period" on a
> source with type=exp. I can't see any reason why it shouldn't be
> possible, except that it would probably be necessary to ensure you don't
> get an abrupt transition at the start of a new period (given that it
> will never actually reach the final value with an exponential source).
>
> You should contact Cadence sup****t, and an enhancement request could be
> filed on your behalf.
>
> Regards,
>
> Andrew.
>
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