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I had a simple netlist down here:

Example netlist
v1 1 0 dc 15
r1 1 0 5k
.end

Yes, I could just calculate the power lost in here which yield about 45 mW. But the thing is, is there a command for ngspice to print the temperature of certain a device?

I'm using ngspice-31.

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  • \$\begingroup\$ SPICE models don't generally include information on thermal resistance, do they? \$\endgroup\$ – Hearth May 18 '20 at 13:41
  • \$\begingroup\$ @Hearth shocked that's new to me. \$\endgroup\$ – harieamjari May 18 '20 at 13:43
  • \$\begingroup\$ I'm not aware of any way to get SPICE to consider thermal effects at all, but I'm not an expert in SPICE by any means. \$\endgroup\$ – Hearth May 18 '20 at 13:45
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But the thing is, is there a command for ngspice to print the temperature of certain a device?

How can any spice tool know what the thermal conductivity of the device is to ambient. Temperature is not directly related to power - it is the result of power crossing from a hot object to an object of different temperature - that boundary material that exists between the two objects has a thermal conductivity (a material constant measured in watts per metre-kelvin) and does spice know what medium exists between your resistor and ambient temperature?

Sure, spice will know about the ambient temperature. For instance, micro-cap defaults to 27 degC but it cannot know about the material surrounding the resistor.

That material is usually quite complex too - it's circulating air and a thermal mass of copper (maybe) and PCB material. The dynamics are also quite significant because not only is there thermal conductivity to consider but the specific heat capacity of the material. The specific heat capacity is in units of is joule per kelvin per kilogram and tells you how much something warms with a heat energy input. You would use it for dynamic temperature estimations before thermal conductivity numbers kick in to play.

Then, what would spice make of the internal junction temperature of this device or that device or the shape of your resistor.

No, you have to calculate this yourself but, once you have established the thermal resistance of the device in its surroundings you can factor that in the any spice calculation.

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