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Simulators >> AMS Simulators >> Problem simulating with AMS Simvision
https://designers-guide.org/forum/YaBB.pl?num=1336414287

Message started by mtp3 on May 7^th, 2012, 11:11am

Title: Problem simulating with AMS Simvision
Post by mtp3 on May 7^th, 2012, 11:11am

Hi!

I am new to AMS and all so excuse if my question is very basic. I am trying to simulate 2 inverter connected in a chain with the first inverter made from actual PMOS/NMOS transistors and the second is a functional description of a not gate with the code being

module inv(x,y)
input x;
output y;

not(y,x)
end module.

Now I have setup the connection files as described in the link below for 1.2V. The only thing I change is the Vsup=1.2, Vthi=0.666, Vtlo=0.333, Vlow=0.

Now the issue I am facing is that the output of the second inverter (the one with functional description) is not what I would expect it to be. I have attached the figure below. The top waveform is the input pulse, the second wave is the output of the schematic level inverter and the last one is the output of the inverter with the functional description. Please guide me if I am doing something wrong or is there a setting that needs to be changed.

http://www.designers-guide.org/Forum/YaBB.pl?num=1249327323

Title: Re: Problem simulating with AMS Simvision
Post by boe on May 8^th, 2012, 2:32am

mtp3,
you seem to use sample&hold for the digital signal.

- B O E

Title: Re: Problem simulating with AMS Simvision
Post by mtp3 on May 8^th, 2012, 2:53am

Thanks for the reply boe,

I also thought so, but since I have not specified any thing the block description or the schematic I am confused what is causing it.

Could it be something that occurs due to the connect files?

Secondly I noticed in the connect file the Tr is 0.2ns do you think that might be the issue?

Title: Re: Problem simulating with AMS Simvision
Post by boe on May 8^th, 2012, 3:42am

mtp3,

it is default behavior of the wave viewer for digital domain signals.

- B O E

Title: Re: Problem simulating with AMS Simvision
Post by mtp3 on May 8^th, 2012, 4:22am

hmmmmm but I am confused in the tutorials that are available with AMS they appear to ideal like the first two forms.

Is there a setting to change this view or something or will I have to live with it?

Title: Re: Problem simulating with AMS Simvision
Post by boe on May 8^th, 2012, 5:46am

mtp3,

Format->Trace in SimVision Waveform Viewer.

- B O E

Title: Re: Problem simulating with AMS Simvision
Post by mtp3 on May 8^th, 2012, 8:02am

Many thanks for the reply boe you are a life saver :). I just noticed that we can plot the same data in the ade window using direct plot but that would be the same as setting the trace to Analog/Linear, right?

My last question(hopefully) if I were doing a mixed signal simulation what Trace option would you recommend?

Title: Re: Problem simulating with AMS Simvision
Post by boe on May 8^th, 2012, 9:38am

mtp3,
Analog/Linear for time-continuous signals, Analog/S&H for time-discrete signals.

- B O E

Title: Re: Problem simulating with AMS Simvision
Post by mtp3 on May 9^th, 2012, 3:23am

Thanks for the replies boe. They were of great help. I solved the issue by compiling the connect rules with a much smaller rise time (10ps instead of 0.2ns) and changing the views also helps.

Thanks for all the help.