TABLE OF CONTENTS A gate turn-off thyristor (known as a GTO) is a three terminal power semiconductor device. GTOs belong to a thyristor family having a four-layer structure. GTOs also belong to a group of power semiconductor devices that have the ability for full control of on-and off-states via the control terminal (gate). To fully understand the design, development and operation of the GTO, it is easier to compare with the conventional thyristor. Like a conventional thyristor, applying a positive gate signal to its gate terminal can turn-on to a GTO. Unlike a standard thyristor, a GTO is designed to turn-off by applying a negative gate signal.
GTOs are of two types: asymmetrical and symmetrical. The asymmetrical GTOs are the most common type on the market. This type of GTOs is normally used with a anti-parallel diode and hence high reverse blocking capability is not available. The reverse conducting is accomplished with an anti-parallel diode integrated onto the same silicon wafer. The symmetrical type of GTOs has an equal forward and reverse blocking capability.
The symbol of a GTO is shown in Fig. 7.1a. A high degree of interdigitation is required in GTOs in order to achieve efficient turn-off. The most common design employs the cathode area separated into multiple segments (cathode fingers) arranged in concentric rings around the device center. The internal structure is...
