IRF740 Package:TO-220
MOSFETS are now the most common switching semiconductor in the world today. They have replaced the common transistor for several key reasons. They are smaller and cheaper to manufacture meaning the equipment where they are used can be smaller and lighter. They have a very high input impedance which reduces loading on circuits.
A high frequency bandwidth makes them ideal for digital and radio frequency applications and they also consume much less DC power than a standard transistor.