This is a question about history.
Does anybody know *if/why* pre-3.0 SPICE could not handle negative inductors and/or capacitors?
When I try the demo circuit from [1], a very popular SPICE cannot handle it and shows exponentially growing waveforms when asked for a .TRAN. Another SPICE (ngspice) has no problem at all. Both SPICE's calculate a .AC request without a hitch and produce the same result.
Netlist:
Code:.TITLE negindcap
V2 in 0 PULSE(0 1 0 1u 1u 5u 10u) AC=1
L2 N001 N002 1nH
R2 out 0 100
C1 out 0 -1pF
L1 N001 out 1nH
L3 in N001 -1nH
C2 N002 0 1pF
* ac dec 100 1G 100G
.options method=gear reltol=1m
.tran 0 {1m+30u} 1m uic
.end
-marcel
Ref: K. B. Kumar, "
Negative inductors and capacitors for SPICE simulation," in IEEE Circuits and Devices Magazine, vol. 6, no. 6, pp. 11-, Nov. 1990.