How to modify gate drive?

Schematic Simulation (Ngspice)
1

I created gitlab project where I put some examples to

. In addition of your 4 examples, I wanted to simulate the n-channel fet, p-channel fet, npn bjt transistor and pnp bjt transistor for controlling the led with 3V3 signal. PNP BJT project has some problems, so that one is still missing but other 3 are now there and working.

There are however some problems that could be interested in also for your examples.
I would also like to try out to modify these examples for 1v8 signal because for that it is often harder to find proper transistors and fets to control the on/off for leds.
With npn bjt example the simulation worked simply by changing the “Pulsed Value (y2)” from V2/Symbol Properties/Simulation Model from 3.3V to 1.8V but with FET examples something more is needed to do.

If V2 voltage is 3.3V on project kicad_spice_models.git/io_pin_3v3_npn_fet_led_control, then the Id2 and Vdrain follow the Vgate voltage and it works as a switch. (See attached picture)
But if I change the V2 voltage to 1.8V, then the Vdrain stays all the time up and Id2 all the time 0. So I should propably need to change some parameter from NPOS fet spice model, but I do not know which one?

npn_fet_1v8_problem_with_kicad_spice
npn_fet_1v8_problem_with_kicad_spice3072×1920 261 KB

npn_fet_3v3_ok_with_kicad_spice
npn_fet_3v3_ok_with_kicad_spice3072×1920 255 KB

2

Your last post is a little off-topic, as this thread is about my tutorial. and should not be used for anything else.

3

Moved from the ngspice tutorial thread

4

Best would be to search for a suitable low voltage FET and its spice model on the web, as this procedure delivers realistic simulation data.

Second best is to change the vto parameter of the VDMOS. The default vto is 3 V (not 0 V as stated in the parameter list). Change it to 1 V. Of course this resembles then a generic device, not a realistic device.

It is useful to learn a little about the devices used in simulation, so about basic MOSFET parameters…