What is a semiconductor diode?
A diode is a two-terminal device formed by two doped regions of silicon separated by a pn junction. The most common category of diode, known as the general-purpose diode,is covered.
Other names, such as rectifier diode or signal diode, depend on the particular type of application for which the diode was designed. You will learn how to use a voltage to cause the diode to conduct current in one direction and block in it the other direction. This process is called biasing.
- Recognize the electrical symbol for a diode and several diode package configurations
- Apply forward bias to a diode
- Define forward bias and state the required conditions
- Discuss the effect of forward bias on the depletion region
- define barrier potential and its effects during forward bias
3. Reverse bias a diode
- Define reverse bias and state the required conditions
- Discuss reverse current and reverse breakdown
As mentioned, a diode is made from a small piece of semiconductor material, usually silicon, in which half is doped as a p region and half is doped as n region with a pn junction and depletion region in between.
The p region is called the anode and is connected to a conductive terminal. The n is called the cathode and is connected to a second conductive terminal. The basic diode structure and schematic symbol are shown in above figure.
Typical Diode Packages
Several common physical configuration of through-hole mounted diode are illustrated. The anode (A) and cathode (K) are indicated on a diode in several ways, depending on the type of package. The cathode is usually marked by a hand, a tab, or some other feature. On these packages where one lead is condition to the case, the case is the cathode.
Surface Mount Diode Packages
Typical diodes packages for surface mounting on a printed circuit board. The SOD and SOT packages have gullwing shaped leads. The SMA package has L-shapes leads that bend under the package. The SOD and SMA types have a band on a end to indicate the cathode. The SOT type is a three terminal package in which there are either one or two diodes. In a single-diode SOT package, Pin 1 is usually the anode and usually pin 3 is the cathode. In a dual-diode SOT package, pin three is the common terminal and can be either the anode or the cathode. Always check the datasheet for the particular diode to verify the pin configurations.
Typical diode packages with terminal identification. The letter K is used for cathode to avoid confusion with certain electrical quantities that are represented by C. Case type numbers are indicated for each diode.
Semiconductor diode (video)