How Does a MOSFET Transistor Work?

MOSFETS in a circuit provide better performance than BJTs.

MOSFET transistors are the most popular types of semiconductors today. MOSFETS have, in effect, replaced bipolar transistors particularly in harsh electrical environments that would destroy bipolar transistors.

Digital

By effectively blocking any Direct Current (DC) from flowing in the channel, MOSFETS reduce power consumption and allow for large impedances or resistances which, in turn, results in a high fanout capacity. This isolation between the gate the channel is used by designers to improve performance.

Analog

Since MOSFETS can be operated at zero gate current voltages as well as zero drain-source voltages, they are ideal switching devices. In addition, they can be etched on a silicon chip to act as precision resistors and capacitors, giving birth to complete analog circuits on a single chip.

As Switches

Drive voltages applied to the gate terminal of a MOSFET can be used to turn a MOSFET ON or OFF. The rate of switching can also be driven and allow for passing of both high and low currents. This control over MOSFETS makes them more efficient as switches compared to bipolar junction transistors.

References

• Electronics Tutorials: The MOSFET as a Switch
• EE Times Design: An Introduction to Depletion-Mode MOSFETS

Resources

• Read this Article in Spanish
• International Rectifier: Power MOSFET Basics