> hello *,
> Florian and me were playing around, trying to start a digital
> simulation. Attached are NOR, OR, NOT, NAND, AND in TTL (wich seem to
> work) and an attempt of a NOT in CMOS. the CMOS version does not work at
> all and we dont understand why.
> symptom is:
> ERROR: TR1: Jacobian singular at t = 2.000e-03, aborting transient
> does anyone have an idea what may cause this? is the circuit wrong or is
> that a shortcoming of the simulator?
definitely a "shortcoming of the simulator". i will try my luck.
hopefully it is going to be a problem with the device model, and not
with the transient simulation...
> furthermore we have same suggestions:
> * for digital circuits we would need some kind of a "table-driven"
> voltage source. something where you just would enter a timespan and a
> 1ms 1V
> 2ms 0V
> 1ms 1V
you are refering something like a pwl source used in spice? pwl = piece
wise linear, right? i put that on my todo list.
> this would be even better when the source had multiple ports, each
> having its own table.
no, rejected :-)
> this way one could simulate digital circuits using analog subcircuits as
> building blocks. the simulation would probably be slower than for a
> proper digital simulation, but you could simulate mixed-mode stuff this
> way. ...or simply teach digital circuits :)
i agree. as long as we don't have a real digital simulation...
> keep up the good work, it's really fun using qucs!
thanks. you're welcome.