A power device may be classified as one of the following main categories (see figure 1):
- A two-terminal device (e.g., a diode), whose state is completely dependent on the external power circuit to which it is connected.
- A three-terminal device (e.g., a triode), whose state is dependent on not only its external power circuit, but also the signal on its driving terminal (this terminal is known as the gate or base).
Another classification is less obvious, but has a strong influence on device performance:
- A majority carrier device (e.g., a Schottky diode, a MOSFET, etc.); this uses only one type of charge carriers.
- A minority carrier device (e.g., a thyristor, a bipolar transistor, an IGBT, etc.); this uses both majority and minority carriers (i.e., electrons and electron holes).
A majority carrier device is faster, but the charge injection of minority carrier devices allows for better on-state performance.
#main source: http://en.wikipedia.org/wiki/Power_semiconductor_device