Andrew Beckett
Senior Fellow
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Life, don't talk to me about Life...
Posts: 1742
Bracknell, UK
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Well, the first one is fairly evident. You have a negative capacitance in the device model.
The second is because small resistors are not a good idea for spectre, because it leads to convergence difficulty (put shortly, this is because of trying to ensure Kirchoff's laws are maintained, and so when the normal numerical methods are used to compute the voltages at the resistor terminals, these would have to be done to excessive precision in order to get the current across this small resistor to be computed correctly to meeting Kirchoff's law). I think this is covered rather more eloquently/clearly in Ken's book, if I remember rightly.
Regards,
Andrew.
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