The transistor family of semiconductor devices is broken into two major classes: fieldeffect transistors and potential-effect transistors (PET). Within the class of PETs lie all types of bipolar transistors, and our second transistor target: the bipolar junction transistors (BJT). The unique property of transistors that makes them indispensable for the implementation of complex electrical systems is that they possess inherent gain. Rectifiers are ubiquitous in power generation, conversion, and transmission. Transconductance in the electronics world just means the incremental change in current divided by the incremental change in voltage. The base transit time typically sets the speed limit of BJTs, this bandgap engineering trick can dramatically improve the speed of the transistor, with only modest changes to the underlying doping profile. The transistor can serve in one of two fundamental capacities: amplifier or regenerative switch.