A MOSFET works when a voltage is applied between the gate and the source. The MOSFET will turn on, and will allow current to flow from the drain to the source. A MOSFET typically, can be used as a signal amplifier similar to a power transistor. This is what is called linear operation of the device. However, the most common use of the MOSFET is the commutation between conduction and interdiction states, as a solid state switch. In most of the applications, this device is able to perform thousands of commutations per second.