EET-123 Lecture Notes - Lecture 3: To-220, Rectifier, Electrical Network
Document Summary
Four-layer diode: the four-layer diode is a fundamental building block for a class of semiconductors known as thyristors. The original four-layer diode had only two terminals and is now obsolete but forms a good starting point to study other four layer devices: thyristors are 4 layer devices consisting of alternating p- and n-material. These devices act as switches; for this reason, they are most frequently used in control applications. (a) 4-layer diode (b) scr (c) diac (d) triac (e) scs. The original 4-layer diode (or shockley diode) acts something like an ordinary diode but conducts in the forward direction only after a certain anode to cathode voltage called the forward-breakover voltage is reached. The 4-layer diode had only two leads, labeled the anode (a) and the cathode (k). The symbol reminds you that it acts like a diode. It does not conduct when it is reverse-biased.
