For the longest time, I've stayed away from FETs and MOSFETs (when it comes to using discrete transistors in my circuits, that is). I'm taking a current hobby project as an excuse to try and finally get comfortable with using them. However, I can't seem to make heads or tails from these beasts.
Before trying any real circuits, I'm running basic (almost "sanity check") LTspice simulations. Extremely simple circuits, and they still don't seem to work. For example, see this LTspice screen capture below — the voltage probe is at the output of the power supply; the current is measured through the resistor connected to the Drain pin. It is supposed to be 1mA when the MOSFET conducts (V2 is 12Volts), and I expect it to go back to 0mA for 1μs when the input voltage is 0V:
BTW, if I make V1 a DC source, then it works: I set it to 0V and the current through R1 is 0mA (well, in the order of pA), and if I set it to 5V, current is 1mA.
What am I missing? I also tried with a 100Ω resistor from V1 to the gate; it just makes a little round-ish bump in the current when switching, but it still does not come back to 0mA. I also added a 10k resistor from gate to GND. See image below, showing the output of the simulation (and again: what am I missing?):
I do have some more concrete questions on the topic, but I figure I better get comfortable with the simplest "toy" circuits before I try to do any "real" applications (even in the context of hobby projects).