Negative time


To "'ng-spice@ieee.ing.uniroma1.it'" <ng-spice@ieee.ing.uniroma1.it>
From "Gillespie, Alan" <Alan.Gillespie@analog.com>
Date Thu, 26 Apr 2001 10:49:50 +0100
Delivered-To mailing list ng-spice@ieee.ing.uniroma1.it
Mailing-List contact ng-spice-help@ieee.ing.uniroma1.it; run by ezmlm
Reply-To ng-spice@ieee.ing.uniroma1.it


> The source starts at the threshold voltage of 5 due
> to the delay of -2n, then it goes up to 10, then falls to 0.
> The switch should start in the on position and stay on until 
> the source
> voltage falls below 4v.  However, with my old spice code, the output
> oscillates at the onset of the transient.
> 
> VCS_Test.ckt
> V1 77  0 DC 12.5
> R1 4  0  1K
> S1 77  3  33 0 S2_switch on
> V2 33  0 DC 5 PULSE( 0 10 -2n 4n 4n 2n 10n)
> R2 33  0  1K
> VAm1 3  4 0
> IVm1 33  0 0
> .model S2_switch SW  vt = 5   vh = 1   ron = 1   roff = 1gig
> .OPTIONS  gmin = 1E-12  reltol = 1E-4  itl1 = 500  itl4 = 500
> .TRAN  1u 10n 0 .5n uic
> .IC  V(33)= 5
> .END

Wow ! I'd never have expected spice to handle things
which "happened" before the simulation started. But I
suppose there's no reason why it shouldn't handle these
simple things, if it can be implemented simply.


Partial thread listing: