SYNOPSIS

PN junction diodes and Bipolar junction transistors (BJTs) are used in a wide variety of switching applications, such as, TV deflection circuits, motor drives, switched mode power supplies and others. In most of these applications, the diodes and transistors are used for operation at frequencies less than 100 kHz. The limiting mechanism for the speed of operation is the presence of stored minority charge during the ON state and the reverse recovery time required for removing these stored charges. The uni-polar devices like Schottky and MOS are inherently fast because of absence of minority charge storage but also have the disadvantage of lower reverse breakdown voltage and higher heat dissipation in comparison to bipolar devices. The Insulated Gate Bipolar Transistor (IGBT) has low on-state losses but due to its relatively involved technology, it is restricted to higher end devices. Even with the limitations as compared to Schottky, 2 2 MOSFET and IGBT, the PIN rectifiers and BJT are still used in various applications. There have been developments to enhance the switching performance of diodes an