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https://designers-guide.org/forum/YaBB.pl Simulators >> Circuit Simulators >> How to plot I-V C-V curve of MOS using Spectre https://designers-guide.org/forum/YaBB.pl?num=1175070667 Message started by ywguo on Mar 28th, 2007, 1:31am |
Title: How to plot I-V C-V curve of MOS using Spectre Post by ywguo on Mar 28th, 2007, 1:31am Hi, Guy, I have a fool question, how to plot I-V C-V curve of MOS transistor using Spectre? I used to run simulation using HSPICE. :( BTW, I think a good manual is important for engineers. Would you please recommend any manual or books about Spectre? Thanks Yawei |
Title: Re: How to plot I-V C-V curve of MOS using Spectre Post by Geoffrey_Coram on Mar 28th, 2007, 5:13am Put in a "save" statement to get the capacitances: save m1:all You can also run an ac analysis with a swept dc bias ac1 ac freq=0.1591549 dev=vd start=0 stop=1.8 which sets the frequency to 1/(2 pi) such that imaginary currents are exactly equal to the capacitances. (You do have to look out for internal resistors, though, which will distort the results.) For *using* Spectre, the built-in help (spectre -help) is good enough for me; Ken did write the Designer's Guide to Spice and Spectre if you want to know more about the internal workings. |
Title: Re: How to plot I-V C-V curve of MOS using Spectre Post by John O Donovan on Mar 28th, 2007, 9:51am Hi, Off topic, but Spectre has a set of builtin mathematical and physical constants that can be used in expressions. Run "spectre -h constants" to get the list. (1) % spectre -h constants So you could use "freq=1/(2*M_PI)" in the ac analysis. Regards, John |
Title: Re: How to plot I-V C-V curve of MOS using Spectre Post by imd1 on Mar 29th, 2007, 1:41am Do you know if it's possible to use similar built-in constants in ELDO or HSPICE ? I find this rather useful, and I've been looking for a way to automatically obtain the thermal voltage during a simulation. |
Title: Re: How to plot I-V C-V curve of MOS using Spectre Post by Croaker on Mar 30th, 2007, 9:07am Geoffrey_Coram wrote on Mar 28th, 2007, 5:13am:
Yes, this is a very good tip, assuming the resistance is low. Also, you can use the CAPTAB option to get the node caps at an operating point. Is there any way to do a DC sweep and plot the CAPTAB results for a node, similar to the 'save m1:all' tip? |
Title: Re: How to plot I-V C-V curve of MOS using Spectre Post by ywguo on Apr 4th, 2007, 1:36am Hi, Geoffrey, I use save m1:all. However, may I save them in analog design environment? Furthermore, how to plot them in wavescan? Thanks yawei |
Title: Re: How to plot I-V C-V curve of MOS using Spectre Post by Geoffrey_Coram on Apr 4th, 2007, 7:39am I don't use the analog design environment, nor wavescan, actually. But I know other threads on this forum have covered plotting "gm" in wavescan, and I would expect the capacitances to work the same way. You might have to look out for problems like "m1" being a subcircuit, so that the actual device that has the operating-point info is "m1.m" |
Title: Re: How to plot I-V C-V curve of MOS using Spectre Post by Croaker on Apr 4th, 2007, 9:53am Yes, you can pull up the results browser and put the results into the calculator to plot the dc op stuff vs. whatever. |
Title: Re: How to plot I-V C-V curve of MOS using Spectre Post by Andrew Beckett on Apr 11th, 2007, 7:53am To answer the question about saving them in ADE, you need to create a text file and put the save statement(s) in there, and then include this file in the simulation. The simplest way of doing this is to use Setup->Model Libraries and reference the file there (Model Libraries are effectively any spectre syntax file - they don't necessarily have to be models). Regards, Andrew. |
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