Simple CMOS Schmitt simulation

Dec 09, 2004 2 Replies
T

Can anyone see why this simple CMOS Schmitt does not simulate reliably please?



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For CircuitMaker users, here's the circuit:

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I don't even get an error message. But the input signal, which should be several cycles of a triangular wave, just stops abruptly. Yet, if I replace the generator with a direct connection to either 0V or 5V, I get the correct simulated output (0V or 5V respectively).



It seems the value of R1 is critical. When I lowered that to 519k, the circuit simulated correctly. At 520k it failed!



Any insight as to the underlying cause please?


Terry Pinnell Hobbyist, West Sussex, UK
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T

OK, thanks Fred, here's the netlist

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But in CM it's trivially easy to just place and connect the 2 NORs, 2 Rs and the source. I'd assumed that's what a non-CM user might do to see if the same simulation issue arises?

Terry Pinnell Hobbyist, West Sussex, UK
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F

"Terry Pinnell" a écrit dans le message de news: snipped-for-privacy@4ax.com...

Terry, the CKT file format is CM proprietary and almost unintelligible. Please post a spice netlist (.cir file) and also the NOR subckt in case they are not included in the .cir file.

Thanks, Fred.
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