A simple demonstration of a low side power switch using an N channel MOSFET. In this example the MOSFET is being used to drive a simulated relay. Just press F8 to run the simulation. The Infineon IPW60R041C6_L0 spice subckt model is in the EasyEDA library. To create a simulation using this device, simply place the NMOS_E symbol from the EasyEDA Libs in the left hand Navigation panel, select the symbol in the schematic, press the 'I' key, then change the 'Spice Prefix' from 'M' to 'X' and click OK. Then double click on the 'NMOS_E' name, change it to 'IPW60R041C6_L0' then click back on the schematic canvas. Done! For a logic level gate drive (Vgs) such as 5V or 3.3V then a so-called 'Logic Level' input MOSFET must be found. The minimum On-State Drain Current ID(ON) at this Vgs must be greater than the maximum current drawn by the load. In this case the load is the resistance of the relay coil. Since the MOSFET should be chosen for the lowest available ON resistance,(Rds_on @ Vgs), then the voltage drop across the MOSFET, the maximum drain current can simply be approximated as: VDD/(the minimum relay coil resistance) BTW, the RELAY_SPDT_EE spice model and symbol are in the library too. Just do a SHIFT+F search with the Editor in SIM mode for: 'RELAY_SPDT_EE', place it in the schematic and it will run in simulation.