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I am using LTSpice to simulate an energy harvesting circuit, so I am very careful with small leakage currents and losses. This circuit is all discretes (Diodes and FETS) and passives. Is there any way to simulate the ranges of some of the parameters, like the gate threshold?

I am already familiar with the Pspice commands to set the temp, but Vgs has a range of 0.5 to 1.5V at 25C, and I would like to be able to see how the circuit functions across the full range. Failing that, I would like to see what Vgs is without doing a whole other test.

The components I am using are part of the default LTSpice library, so I am not sure if I can see the model.

Any advice?

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You can add an ideal voltage source in series with the gate terminal. Changing the voltage on the source will roughly simulate changes in the threshold voltage of the MOSFET.

Most SPICE models are intended to fit the typical behavior of a device, not the full range of parameters nor any failure modes. The model parameters are often determined by optimizing a "best fit" between the model equations and the actual device rather than calculating the parameters from device physics. Depending on the complexity of the MOS model there may be a number of parameters that determine the effective threshold voltage so you can't just pick one parameter and sweep it.

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