Hi,

I am trying to import the model of the GS66508B using the the level 3 model. But i keep getting the following messages.

Didn’t find a model for “Q•X1” – defaults assumed.

Ignoring capacitor: “C_GS1•X1”

Didn’t find a model for “Q•X1” – defaults assumed.

Ignoring capacitor: “C_GS2•X1”

Didn’t find a model for “Q•X1” – defaults assumed.

Ignoring capacitor: “C_GD1•X1”

Didn’t find a model for “Q•X1” – defaults assumed.

Ignoring capacitor: “C_SD1•X1”

Is there a way to solve this ? I import by opening the ltspice version of the model and copy the whole file like in the example.

OK, it was having trouble recognizing a Q=… capacitor when scoped to a subcircuit. That’s fixed now.

QSPICE does have a Q=… capacitor, but it’s an unrelated implementation from that in LTspice. I developed the one in LTspice for modeling the nonlinear overlap capacitance of a vertical power MOSFET. It only really worked right if the charge depended only on the voltage across that capacitor.

The arbitrary reactances in QSPICE correctly handles charge even if the charge depends on voltages that aren’t connected to the capacitor. Such a charge dependence is called transcapacitance(capacitance at a distance, like transconductance).

This simulation demonstrates an electrostatic generator implemented as a motor(V2) connected to an air-variable capacitor(C2):

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Thank you for the fast response

So, we are getting improved FET modeling - that’s fantastic!

QSPICE introduces new aspects to the FET device equations: Subthreshold conduction and the ability to match both the saturation and linear regions. The Shichman-Hodges equations are in error and can’t match both regions.

–Mike

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