well, there are lots of types of transistors. BJTs, JFETs, MOSFETs (Enhancement mode MOSFETs and Depletion Mode MOSFETs), Darlington Transistors, IGBT (Insulated Gate Bipolar Transistor), MESFET, HEMT, PHEMT, UJT (Unijunction Transistors), VMOS Transistors........... and the list goes on.