Discrete power semiconductors are large, stand-alone discrete-component semiconductors that are used as rectifiers or as switching devices, usually in power supplies or in power electronic circuits, designed to convert or condition electric power. Some of the more familiar discrete power devices used in a typical discrete power supply are the power MOSFET, the IGBT, the thyristor and the PiN diode.

Discrete power semiconductors are either two-terminal devices (e.g. PiN diodes and Schottky diodes) or three-terminal devices (e.g. power MOSFETS, JFETs, IGBTs, BJTs and thyristors), which are all examples of discrete power transistors. Both two- and three-terminal categories are further categorized by whether they are minority carrier devices or majority carrier devices. When searching the products available from discrete power semiconductor suppliers for components for your project, consider the following:

1. Use minority-carrier devices when discrete power semiconductors with superior voltage characteristics are required.

2. Use majority-carrier devices when discrete power semiconductors are required for high-frequency/high-speed applications.

3. For really high power three-terminal applications, use thyristor-based transistors, e.g. SCRs, GTOs and MCTs.

Action Steps
The best contacts and resources to help you get it done

Buy discrete power diodes and thyristors for high off voltage and low on voltage applications

When the device you are building requires discrete power semiconductors with the characteristic of high voltage swing between on and off states, then the diode of choice is the PiN diode and the transistors to consider include the thyristor, the bipolar junction transistor (BJT), and the insulated gate bipolar transistor (IGBT). These are all minority carrier devices.

I recommend: C&H Technology carries a variety of thyristors, in addition to IGBTs and rectifier diodes. On Semiconductor has your BJT needs well-covered for a range of applications.

Buy discrete power devices for high-frequency applications

When the device you are building requires high-frequency or fast-switching discrete power semiconductors, then the diode of choice is the Schottky diode and the transistors to consider include the metal oxide semiconductor field effect transistor (MOSFET) and the junction gate field effect transistor (JFET). These are all majority carrier devices.

I recommend: Mouser Electronics has an impressive selection of Schottky diodes. ST Microelectronics has just about every power MOSFET you will ever need.

For fast-switching and high voltage, get new-technology silicon carbide (SiC) discrete power devices

A new-technology SiC version of discrete power diodes and transistors has emerged recently. SiC Schottky diodes and SiC JFETs still have the high-speed capabilities of their silicon predecessors, but also have very high voltage-handling capabilities as well. SiC Schottky's and SiC JFETs will handle voltages of up to 1200V. SiC bipolar transistors can operate with voltages of up to 20 kV. A manufacturer interested in producing SiC discrete power semiconductors should contact one of the following SiC wafer makers.

I recommend: If you are wanting to produce SiC discrete power semiconductors, BAE Systems will manufacture the SiC wafers for that purpose. SemiSouth makes SiC wafers, but it has also developed a line of discrete power semiconductors, such as Schottky's and FETs, that you can purchase. SemiSouth also has received a patent for its SiC manufacturing process.

Tips & Tactics

Helpful advice for making the most of this Guide

• •  Schottky diodes have among the fastest switching times and lowest forward voltage drop of any power semiconductor. However, if you need the forward voltage drop to be even lower yet, or if reverse leakage would be a problem, you can use a combination of a MOSFET and a control circuit to make an 'ideal diode' and use its continuous rectification mode.