Power tool devices described herein include a housing, a power source interface, a field effect transistor within the housing connected between the power source interface and a load of the power tool device, and an electronic processor coupled to the field effect transistor. The electronic processor is configured to control the field effect transistor to drive the load and measure a voltage at a terminal of the field effect transistor. The electronic processor is also configured to determine the current flowing through the field effect transistor based on the voltage without using a shunt resistor.