Solid State Electronic Devices, 7th Edition

10.4 The P-N-P-N Diode

One of the most common applications of electronic devices is in switching, which requires the device to change from an “off” or blocking state to an “on” or conducting state. We have discussed the use of transistors in this application, in which base current drives the device from cutoff to saturation. Similarly, diodes and other devices can be used to serve as certain types of switches. There are a number of important switching applications that require a device remain in the blocking state under forward bias until switched to the conducting state by an external signal. Several devices that fulfill this requirement have been developed, including the semiconductor-controlled rectifier (SCR).⁵ These devices are typified ...