# lec6 > diagrams needed for this section ## Transistors Two types of transistors will be discussed here: `NPN` and `PNP`. Both types however, do share some properties here by referred to as the following: * E = Emitter * B = Base * C = Collector ### NPN ![](../img/lec6npn.png) Current will __not__ flow across collector through base into emitter if do nothing. When we apply a current to the base then current flows through the transistor. ### PNP ![](../img/lec6pnp.png) Current will flow across emitter through base into collector if we don't do anything. When we apply a current to the base then current flow stops.