5. The MOSFET (Metal Oxide Semiconductor Field Effect Transistor): The Efficient Digital Switch
A MOSFET is a type of transistor commonly used for switching electronic signals in both digital and analog circuits.
Key Characteristics
- Isolated Gate: Its most important feature is a thin layer of silicon dioxide that isolates the gate terminal. This gives the MOSFET an extremely high input resistance.
- Low Power Switching: Because of the isolated gate, it requires very little current (less than one milli-ampere) to be switched ON.
- High Current Delivery: Despite its low switching power requirement, a MOSFET can deliver a high current load of more than 50 Amperes.
Modes of Operation
MOSFETs come in two main forms that determine their default state:
- Depletion State: The device is normally ON and requires a gate-source voltage to be switched OFF.
- Enhancement State: The device is normally OFF and requires a gate-source voltage to be switched ON.
Now that we’ve profiled each device individually, a side-by-side comparison can help solidify their unique roles.