Modelling switches & time in NGSPICE

Question

I want to model the behaviour of a circuit in response to 'pushbutton' actions by a user. That is,

1. Initial state;
2. Simulate momentary button press & new state following;
3. Likewise with a different button.

I haven't used NGSPICE for a looong time, and this sort of thing wasn't something I studied even back then. I haven't found any way to to this, or even to search properly for it, so any suggestions/help/links will be very much appreciated.

Thanks!

Answer 1

You can model initial state of a circuit by specifying node voltages at startup (using the .ic statement).

To model the switch you have a couple of options: 1. Switch Model (SW/CSW) (Ngspice manual 3.2.15) 2. Analog Switch (Ngspice manual 12.2.10) 3. Use a resistance with a parametric value: Rswitch node1 node2 R=v(controlnode) Vcontrol controlnode 0 {expression}