A MOSFET is a metal-oxide semiconductor field-effect transistor with a gate connection isolated from the semiconductor section. It is an active component with at least three connections: a gate, a source and a drain connection. A MOFSET is a voltage-controlled switch: the current flow from the drain to the source is determined by the voltage between the gate and the source. These transistors are divided into n and p types (NMOS or PMOS) with these types indicating which charges help to transmit the power. Negative charges come from the n-types, for example. When the control voltage is connected to the gate connection, an electric field is created which enlarges or reduces the non-conducting substrate, depending on the polarization. The barrier which prevents the current from flowing is created or dissipated by the electric field. Since the gate capacity is only charged once in a MOSFET and then the control current needs to be reduced towards zero, the control electronics need to provide significantly less output. This allows faster switching speeds to be achieved.
The possible high switching frequencies which extend into the MHz range enable smaller inductive components to be fitted when switched-mode power supplies or circuit controllers are used.