Hi QS,
simply to confirm an “elementary” doubt.
As you can see in the figure, in the default netlist from the schematic, in the resistor Rc (collector) it shows a negative value of current that makes a little “damage to the eye” (a positive value would be more pleasant!).
In principle it is logical since I deduce that the order of the nodes matters in the netlist.
The first one is considered to be at a higher potential than the second one.
That’s why I made a test by changing the order to check it.
This has made me to write this message to help me to see what maybe is not important and I am giving too much importance to it.
Thank you. Toni
The +ve current direction in spice for resistor, capacitor, inductor and voltage/current source are defined from 1st net to 2nd net.
There is no default order, it is just because you used Ctrl-R to rotate Rc, and in schematic, its 1nd net go to bottom in your schematic.
You can check net order by
- F3 (View Symbol Properties)
- Click on component
- Goto Pin Nets
- Click pin name you want to highlight
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Therefore, for voltage source, as +ve current direction is from + to -, the current coming out from voltage source is -ve. In Qspice, when you place a current probe at voltage source Vnnn, waveform viewer in default give you -I(Vnnn). But other spice program may give you +I(Vnnn) and you have to change it to -ve in waveform window.
Based on this principal, a common skill in spice is to use 0V voltage source for current measurement. Here is an example
Third party mosfet current measurement - QSPICE - Qorvo Tech Forum
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