TABLE OF CONTENTS An active electronic component is a circuit component that requires external power to perform its function. The discussion of active components in this section is limited to discrete diodes, transistors, and thyristors. Integrated circuits (ICs), also active components, are covered in separate sections of this handbook. Analog and linear ICs are discussed in Sec. 8, digital ICs and semiconductor memories are covered in Sec. 9, and microprocessors and microcontrollers are covered in Sec. 14.
A small-signal diode is a two-terminal silicon PN junction that can rectify and clip signals. Rated to handle up to 1 W, these diodes are made by growing an N-type region on a P-type wafer so that there is a direct interface or junction between the two different materials. The wafer is then diced and packaged with terminals attached to both sides of the die. The P-type material is the anode and the N-type material is the cathode, as shown in the section view Fig. 2-1 a. The P-type anode contains a surplus of "holes," or vacant sites that can be filled by electrons to conduct current, and the N-type cathode contains a surplus of electrons. The schematic symbol for a diode is shown in Fig. 2-1 b. The arrowhead indicates the direction of conventional current flow, but this is opposite to electron flow, indicated by the arrow pointed in the opposite direction.
