Diodes are sometimes called rectifiers because they change alternating current (AC) into pulsating direct current (DC). Diodes are rated according to the voltage, kind, and current they can handle. A diode's polarity is determined by its cathode, or negative lead, and anode, or positive lead. Most diodes only allow current to flow in the presence of a positive voltage applied to the anode. An electrical component with two terminals that permits current to flow in one direction while obstructing it in the other is called a diode. It is among the most basic and straightforward semiconductor components found in electronic circuits. Diodes are semiconductor devices that have a P-N junction and are commonly composed of silicon or germanium.
What is a Diode Symbol?
The diode symbol appears as an arrow pointing in the direction of normal current flow in circuit diagrams. It consists of a triangle pointing perpendicular to the route of the arrow toward a short line. The triangle represents the anode (positive terminal), and the line represents the cathode (negative terminal).
Diodes come in many different shapes and sizes, each with a unique symbol that indicates its unique properties and applications in electrical circuits. Conventional rectifier diodes employ the basic arrow symbol (₷|), whereas specialized diodes have customized symbols. For instance, Light Emitting Diodes (LEDs) are recognized by their outward-pointing arrows, Zener diodes by their voltage-regulating "Z"-shaped cathode line, and Schottky diodes by their "S"-shaped cathode line, which denotes their ability to turn on and off quickly. Additional types include varactor diodes with a parallel cathode line for voltage-controlled capacitance, photodiodes with inward-pointing arrows for light sensitivity, and tunnel diodes with a center rectangle indicating negative resistance characteristics. Specialized types like PIN, avalanche, and Gunn diodes have different symbols or modifications. Understanding these symbols is crucial for correctly analyzing and creating electronic schematics because they provide fast visual indications about the type of diode and its intended use inside a circuit.
Semiconductors of the P and N types are used as diode materials. P-type semiconductors, so-called because the majority of their charge carriers are positive holes, are semiconductors doped with boron (B) or another electron acceptor element. Doped semiconductors are known as n-type semiconductors because the majority of their charge carriers are negative electrons, such as arsenic or another element that donates electrons. A pn junction diode can be made by combining n-type and p-type semiconductors. For example, p-type (n-type) semiconductors can produce pn junctions by injecting high-energy p-type (n-type) dopant ions into them.
An electrode terminal linked to a pn junction formed in this way is called a diode. An electrode terminal linked to a pn junction formed in this way is called a diode. (Figure 1)
Only when a diode is forward-biased, or when the anode is more positively biased than the cathode, can electricity flow through it (Figure 2). Rectification is the process that permits current to flow solely in one direction.
Generally speaking, a diode doesn't conduct when reverse-biased. However, when the reverse bias voltage is raised, a diode suffers an abrupt, substantial current flow at a specific value. This voltage is known as the breakdown voltage (VBR). In the breakdown area above VBR, a tiny change in voltage causes a large change in current. Put differently, the voltage changes relatively little in response to a change in current. Two types of diodes designed to capitalize on this constant-voltage nature are Zener diodes and transient voltage suppression (TVS) diodes, also referred to as ESD protection diodes. Figure 3 shows the IF-VF curve of a pn junction diode.
