Re: [Gnucap-devel] "transient" branch

[al davis]

On Fri, 12 Aug 2016 19:48:35 -0400
al davis <address@hidden> wrote:

> "chgtol" is absolute tolerance on charge.  Default value was 10
> femto-Amps. (1e-14)  which corresponds to 1 volt on a 10 femtofarad
> capacitor. This capacitance is common for strays inside a device model,
> so the auto step size was missing these for step control, leading to
> steps too large and the dreaded trap-ringing.  I think it should change
> to .1fA (1e-16).  If this makes steps too small, and run time too slow,
> you should use method=euler or method=gear instead of the default
> method=trap.

Not femto-Amps, it's femto-Coulombs.  Charge is measured in Coulombs.

Those default values made sense in 1975, but today's smaller devices
have less capacitance, less charge.