I’m trying to simulate a soft-start circuit and have trouble getting it to converge. The circuit charges a capacitor via a large resistor and after reaching a certain voltage turns on a P-channel MOSFET to bypass the resistor. Did some other simulations with KiCad and ngspice before, but overall I’m…

Two remarks on your circuit. The model you use is weird it defines the mosfet twice I assume it will be overrun the second time (you can define the PMOS directly or refer to a .model PMOS and your .subckt does both. (in your .mod file) Second the voltage on the switch creeps very slowly to 2 volt …

Trouble getting simple PMOS circuit to converge - help needed

Schematic Simulation (Ngspice)

Piotr April 11, 2025, 10:29pm 2

Read: