Potentiometer TextBox

[paulvdh]

I am not sure about the details, but I have read several times on this forum that ngSpice does not directly support potentiometers, and you have to model it as two resistors and a formula, like in the post below:

Is it possible to perform a simulation with parametric sweep?

Hello, I am trying to perform a simulation in the current nightly build similar to what I do in LTspice. My point is to find some parameter and use this parameter as the value of the component, for example the position of the potentiometer. I would like to achieve something like this in KiCad combined with NGspice: [image] This is what my scheme looks like, I’m trying to sweep the pos parameter… [image] Here is the potentiometer model: .subckt RPOT 1 2 3 value=10k pos=0.5 R2 2 3 {value *…

But when reading the ngSpice manual, apparently it does support potentiometers:

12.2.34 Potentiometer

Description: A resistance potentiometer with three connections: r0, wiper , and r1.
Parameter position determines the lower and upper portions of the resistance.
Rlower is located between r0 and wiper, Rupper between wiper and r1. If log is
set to FALSE, Rlower = position ∗ r. If log is set to TRUE, then
Rlower = r ∗ 10 −position∗log_multiplier . For Rupper we always have
Rupper = r − Rlower. position <= 0 is resolved to position = 1e − 9,
position >= 1 is resolved to position = 0.999999999.

Also, via this search:
https://forum.kicad.info/search?expanded=true&q=potentiometer%20%23schematic%3Asimulation-ngspice

you find:

Basic Potentiometer simulation

I’m trying to have a basic simulation with R_POT but it’s not working. I don’t understand if i need to define a model for R_POT or if i just need to do a .param [Potentiometer]