On Saturday 16 July 2005 12:20 pm, Harold D. Skank wrote: > I need to see the current in a particular branch of a circuit > under SPICE simulation. I understand that a voltage source > set to zero is supposed to be the mechanism to use, but what > variable do I query then to view the current?
As Stuart says, in Spice you need to put a voltage source in and probe it. To put in another plug for gnucap .... There are lots of probes in gnucap. You can simply probe the current in any 2-terminal element, or any of the standard controlled sources. For a resistor R523, ... "print tran i(r523)". For more complex devices, you need to be more specific. For example, a BJT, what current do you want? IC(Q3), IB(Q3), IE(Q3) are the obvious ones. You can also probe a bunch of internal values, including power, currents, internal variables. You can also probe lots of stuff about each the elements that make up the transistor, 14 of them for a fully loaded BJT. You can even separately probe things like the current through internal capacitances, by accessing the internal elements. Spice-3 lets you do some of these for the operating point analysis, with a different syntax. I don't know if it works in ng-spice or not.
