The Diode
As mentioned. a diode is made from a small of semiconductor material. usually piece silicon, in which half is doped as a p region and half is doped as an n region with a pn junction and depletion region in between. The p region is called the anode and is connected a conductive terminal. The n region is called the cathode and is connected to a second conductive terminal. The basic diode structure and schematic symbol are snown in Figure 2-1
Cathode Anode Anode (A) Cathode (K) (b) Symbol a) Basic structure
Typical Diode Packages
several common physical configurations of through-hole mounted diodes are illustrated in Figure 2-2(a). The anode (A) and cathode (K) are indi- cated on a diode in several ways, depending on the type of package. The cathode is usually marked by a band, a tab, or some other feature. On those packages where one lead is con- nected to the case, the case is the cathode.
Surface-Mount Diode Packages
Figure 2-2(b) shows typical diode packages for sur face mounting on a printed circuit board The soD and sor packages have gull-wing shaped leads. The SMA package has L-shaped leads that bend under the package. The SOD and SMA have a band on one end to indicate the cathode. The SOT type is a types three-terminal package in which there are either one or two diodes. In a single-diode sor package, pin is usually the anode and pin 3 is the cathode. In a dual-diode package. in 3 is te common terminal and can be either the anode or the cathode. Always check the datashcet for the particular dode to verify the pin configurations.