[time-nuts] Spice simulation of PSRR and phase noise

[Rafael Gajanec]

Hi Attila,

On 27-Oct-17 8:25 PM, Attila Kinali wrote:
> Hi Rafael
>
> On Sun, 22 Oct 2017 17:20:52 +0200
> Rafael Gajanec<rgajanec at vercet.com>  wrote:
>
>> you haven't specified what sort of circuits would you like to simulate,
> Simplified, they are differential amplifiers driven into saturation.
> A bit more detailed, I am looking at ring oscillator stages and sine-to-square
> conversion circuits and their behaviour regarding various key factors
> (note: I am not sure what the key factors are, yet)
Oscillator design - that's what I found HB simulation particularly 
useful for. It gives you almost instant results, compared to the 
transient simulation, say 10 seconds instead of 5 hours! Just imagine 
what it means if you are trying to tune several parameters of an 
oscillator... The only other reasonably fast and accurate way I can 
think of is to build the bloody circuit and measure it using some 
expensive equipment.
>
>> but maybe the answer is Harmonic Balance.
> Hmm.. I didn't know about Harmonic Balance. I have some reading up to do.
> Thanks!
>
>> HSPICE from Synopsis and ADS from Keysight (which I use) also have the
>> HB engine.
> I am mostly using ngpsice, because it's very easy to script (I have a bunch
> of perl scripts that feed simulations into a Grid Engine cluster, extract
> data and analyzse it). Is there any big advantage of the commercial spice
> engines that would make them worth considering? And would the license alow
> to run hundreds of instances in parallel?
> (Yes, I am doing crazy things :-)
Attached are some results of a simple transient simulation using Hspice 
M 2017.03, BBspice A/D 5.2.3 and ADS 2016.01. It's basically *V1 1 0 SIN 
0 1 1Meg *and then *.FOUR 1Meg V(1)* in Hspice, VspecTran in ADS and 
spectra computed using postprocessor in BBspice and ADS. As you can see, 
there are some differences... To be fair, possibly there are some 
simulator-specific settings/methods that could improve the results and 
you should figure it out yourself what's the way to get the best results 
from your spice. See 
http://www.audio-perfection.com/spice-ltspice/distortion-measurements-with-ltspice.html

Commercial spice engines may have lower computational noise and shorter 
simulation times. For example my out-dated BBspice (which is commercial 
too by the way) crashed several times before I got some results, while 
it used little RAM and only about 10-12% of available processor 
resources... I intended to get you Pspice results of this simulation as 
well, but I gave up after half an hour and about 1% of progress.

>
> 			Attila Kinali

Best regards,
Rafael Gajanec
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