Because they convert alternating current (ac) into pulsing direct current (dc), diodes are often referred to as rectifiers. Diodes are rated based on their voltage, type, and current carrying capacity. An anode (positive lead) and a cathode (negative lead) determine the polarity of a diode. The majority of diodes only permit current to flow when the anode receives a positive voltage.
A diode is a two-terminal electronic component that allows current to flow in one direction while blocking it in the opposite direction. It's one of the simplest yet most fundamental semiconductor devices used in electronic circuits. Diodes are made from semiconductor materials, typically silicon or germanium, and consist of a P-N junction.
In circuit diagrams, the diode symbol is represented by an arrow that points in the direction of regular current flow. It is made up of a triangle pointing in the direction of a short line that is perpendicular to the arrow's path. The cathode (negative terminal) is represented by the line, and the anode (positive terminal) by the triangle.
Diodes are available in a variety of forms, and each has a distinctive symbol that denotes their particular characteristics and uses in electrical circuits. While specialized diodes have modified symbols, conventional rectifier diodes use the fundamental arrow symbol (▷|).
For example, Light Emitting Diodes (LEDs) have arrows pointing outward to signify light emission; Zener diodes have a cathode line shaped like a "Z" to regulate voltage; and Schottky diodes have a cathode line shaped like a "S" to indicate quick switching capabilities. Other varieties are photodiodes with inward-pointing arrows for light sensitivity, tunnel diodes with a central rectangle signifying negative resistance qualities, and varactor diodes with a parallel cathode line for voltage-controlled capacitance.
Specialized varieties with unique symbols or alterations include PIN, avalanche, and Gunn diodes. Since these symbols offer instant visual signals regarding the type of diode and its intended purpose inside a circuit, understanding them is essential for accurately interpreting and developing electronic schematics.
A multimeter's capacity to test diodes for correct functionality is shown by the diode symbol. You may determine whether the diode is operating appropriately by measuring the forward voltage drop and setting the multimeter to diode test mode. To ensure that the diode conducts in one direction and blocks in the other, a good test must examine the diode's reaction in both forward and reverse bias.
With one notable exception, a Zener diode's sign is comparable to that of a regular diode. It is made up of an arrowhead or triangle that points in the direction of the cathode, which is represented by a vertical line. The primary distinction is that the vertical line ends in a little bend that resembles a "Z," signifying the Zener diode's unique characteristics.
Zener Diode Symbol Features
Triangle: Indicates the direction of conventional current flow by pointing toward the cathode.
Vertical Line: Indicates the cathode; the cathode side is usually indicated by a band.
Bend in the Line: The Zener diode is distinguished from a standard diode by the bend at the end of the vertical line, which indicates that the diode can conduct under reverse bias once the breakdown voltage, or Zener voltage, is reached.
In circuit designs, Zener diodes—which are mostly used for voltage regulation and sustaining a stable output voltage under changing load conditions—are made easier to identify for engineers and technicians by this symbol.
A Schottky diode has a unique change to its symbol, which is identical to that of a regular diode. It has a triangle that symbolizes the anode and points in the direction of a vertical line that represents the cathode. The cathode line is extended to resemble a "S," signifying its special characteristics as a Schottky diode, and this is the main distinction.
Schottky Diode Symbol Features
Triangle: Indicates the direction of conventional current flow by pointing towards the cathode.
Extended Cathode Line: The cathode's line is bent, giving it a "S" form that sets it apart from the traditional diode symbol.
This modification emphasizes the qualities of the Schottky diode, which make it appropriate for high-speed applications and rectification in electronic circuits. These qualities include its low forward voltage drop and quick switching capabilities.
