Editing Power semiconductor device (section)

===Amplifiers===
Amplifiers operate in the active region, where both device current and voltage are non-zero.  Consequently power is continually dissipated and its design is dominated by the need to remove excess heat from the semiconductor device. Power amplifier devices can often be recognized by the [[heat sink]] used to mount the devices. Multiple types of power semiconductor amplifier device exist, such as the bipolar junction transistor, the vertical MOS field effect transistor, and others. Power levels for individual amplifier devices range up to hundreds of watts, and frequency limits range up to the lower [[microwave]] bands. A complete audio power amplifier, with two channels and a power rating on the order of tens of watts, can be put into a small integrated circuit package, needing only a few external passive components to function. 
Another important application for active-mode amplifiers is in linear regulated power supplies, when an amplifier device is used as a [[voltage regulator]] to maintain load voltage at a desired setting.  While such a power supply may be less energy efficient than a [[switched mode power supply]], the simplicity of application makes them popular, especially in current ranges up to about one amp.