Power Semiconductors and ICs

Transistors are three-terminal semiconductor devices. One terminal controls electrical resistance or current flow between the other two terminals, giving transistors a valvelike operation. Transistors can amplify signals over some linear range of voltage and current or they can rapidly switch signals between two or more levels. Typical switching circuits include inverters, converters, voltage regulators, and relay and solenoid drivers. Transistors are grouped into two categories: bipolar-junction transistors (BJTs) and field-effect transistors (FETs). The two types of field-effect transistors are metal-oxide semiconductor FETs, or MOSFETs, and junction FETs, or JFETs. Bipolar junction transistors are composed of two junctions formed by three layers of semiconductor material. The layers are called the emitter, base, and collector. An electrical signal (current) applied to the base terminal controls the current between the emitter and collector. The emitter and collector are both made from the same type of material, -type material is negatively doped to have excess electrons, and -type positively doped to be deficient of electrons. In either case, the base material is opposite that of the emitter and collector. The two types of BJTs can be differentiated in schematic diagrams by their circuit symbols. Among the most important transistor characteristics are maximum (voltage between collector and emitter), (current flowing through the collector), power dissipation, and maximum allowable junction temperature (collector junction). Exceeding these values may damage the transistor. Junction field-effect transistors are composed of an -type semiconductor channel with two electrical contacts, called source and drain, at opposite ends. Two junctions, of opposite polarity with respect to the channel, laterally bound the channel along its length. The two