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DIAC
The DIAC (diode for alternating current) is a diode that conducts electrical current only after its breakover voltage, VBO, has been reached momentarily. Three, four, and five layer structures may be used. Behavior is similar to the voltage breakdown of a TRIAC without a gate terminal. When breakdown occurs, internal positive feedback (impact ionization or two transistor feedback) ensures that the diode enters a region of negative dynamic resistance, leading to a sharp increase in current through the diode and a decrease in the voltage drop across it (typically full switch-on takes a few hundred nanoseconds to microseconds). The diode remains in conduction until the current through it drops below a value characteristic for the device, called the ''holding current'', IH. Below this threshold, the diode switches back to its high-resistance, non-conducting state. This behavior is bi-directional, meaning typically the same for both directions of current. Most DIACs have a three ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thyristor
A thyristor (, from a combination of Greek language ''θύρα'', meaning "door" or "valve", and ''transistor'' ) is a solid-state semiconductor device which can be thought of as being a highly robust and switchable diode, allowing the passage of current in one direction but not the other, often under control of a gate electrode, that is used in high power applications like inverters and radar generators. It usually consists of four layers of alternating P- and N-type materials. It acts as a bistable switch (or a latch). There are two designs, differing in what triggers the conducting state. In a three-lead thyristor, a small current on its gate lead controls the larger current of the anode-to-cathode path. In a two-lead thyristor, conduction begins when the potential difference between the anode and cathode themselves is sufficiently large (breakdown voltage). The thyristor continues conducting until the voltage across the device is reverse-biased or the voltage is removed (b ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quadrac
A QUADRAC is a special type of ''thyristor'' which combines a DIAC and a TRIAC in a single package. The DIAC is the triggering device for the TRIAC. Thyristors are four-layer (PNPN) semiconductor devices that act as switches, rectifiers or voltage regulators in a variety of applications. When triggered, thyristors turn on and become low-resistance current paths. They remain so even after the trigger is removed, and until the current is reduced to a certain level (or until they are triggered off). Diacs are bi-directional diodes that switch AC voltages and trigger triacs or silicon-controlled rectifiers (SCRs). Except for a small leakage current, diacs do not conduct until the breakover voltage is reached. Triacs are three-terminal, silicon devices that function as two SCRs configured in an inverse, parallel arrangement. They provide load current during both halves of the AC supply voltage. By combining the functions of diacs and triacs, QUADRACs eliminate the need to buy and assemb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
TRIAC
A TRIAC (triode for alternating current; also bidirectional triode thyristor or bilateral triode thyristor) is a three-terminal electronic component that conducts current in either direction when triggered. The term TRIAC is a genericized trademark. TRIACs are a subset of thyristors (analogous to a relay in that a small voltage and current can control a much larger voltage and current) and are related to silicon controlled rectifiers (SCRs). TRIACs differ from SCRs in that they allow current flow in both directions, whereas an SCR can only conduct current in a single direction. Most TRIACs can be triggered by applying either a positive or negative voltage to the gate (an SCR requires a positive voltage). Once triggered, SCRs and TRIACs continue to conduct, even if the gate current ceases, until the main current drops below a certain level called the holding current. Gate turn-off thyristors (GTOs) are similar to TRIACs but provide more control by turning off when the gate s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shockley Diode
The Shockley diode (named after William Shockley) is a four-layer semiconductor diode. It is a PNPN diode with alternating layers of P-type and N-type material. It is equivalent to a thyristor with a disconnected gate. Shockley diodes were manufactured and marketed by Shockley Semiconductor Laboratory in the late 1950s. The Shockley diode has a negative resistance characteristic. It was largely superseded by the DIAC. Working Unlike other semiconductor diodes, the Shockley diode has more than one p–n junction. The construction includes four sections of semiconductors placed alternately between the anode and cathode in the pattern of PNPN. Though it has multiple junctions, it is termed a diode for being a two-terminal device. The Shockley diode remains in an OFF state, with a very high resistance, until a voltage greater than the trigger voltage is applied across its terminals. When the voltage exceeds the trigger value, the resistance drops to an extremely low value ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diodes
A diode is a two- terminal electronic component that conducts electric current primarily in one direction (asymmetric conductance). It has low (ideally zero) resistance in one direction and high (ideally infinite) resistance in the other. A semiconductor diode, the most commonly used type today, is a crystalline piece of semiconductor material with a p–n junction connected to two electrical terminals. It has an exponential current–voltage characteristic. Semiconductor diodes were the first semiconductor electronic devices. The discovery of asymmetric electrical conduction across the contact between a crystalline mineral and a metal was made by German physicist Ferdinand Braun in 1874. Today, most diodes are made of silicon, but other semiconducting materials such as gallium arsenide and germanium are also used. The obsolete thermionic diode is a vacuum tube with two electrodes, a heated cathode and a plate, in which electrons can flow in only one direction, from ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diode
A diode is a two-Terminal (electronics), terminal electronic component that conducts electric current primarily in One-way traffic, one direction (asymmetric electrical conductance, conductance). It has low (ideally zero) Electrical resistance and conductance, resistance in one direction and high (ideally infinite) resistance in the other. A semiconductor diode, the most commonly used type today, is a Crystallinity, crystalline piece of semiconductor material with a p–n junction connected to two electrical terminals. It has an Exponential function, exponential current–voltage characteristic. Semiconductor diodes were the first Semiconductor device, semiconductor electronic devices. The discovery of asymmetric electrical conduction across the contact between a Crystal, crystalline mineral and a metal was made by German physicist Ferdinand Braun in 1874. Today, most diodes are made of silicon, but other semiconducting materials such as gallium arsenide and germanium are also ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Voltage
Voltage, also known as (electrical) potential difference, electric pressure, or electric tension, is the difference in electric potential between two points. In a Electrostatics, static electric field, it corresponds to the Work (electrical), work needed per unit of Electric charge, charge to move a positive Test particle#Electrostatics, test charge from the first point to the second point. In the SI unit, International System of Units (SI), the SI derived unit, derived unit for voltage is the ''volt'' (''V''). The voltage between points can be caused by the build-up of electric charge (e.g., a capacitor), and from an electromotive force (e.g., electromagnetic induction in a Electric generator, generator). On a macroscopic scale, a potential difference can be caused by electrochemical processes (e.g., cells and batteries), the pressure-induced piezoelectric effect, and the thermoelectric effect. Since it is the difference in electric potential, it is a physical Scalar (physics ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thyristor Surge Protection Device
A surge protector, spike suppressor, surge suppressor, surge diverter, surge protection device (SPD), transient voltage suppressor (TVS) or transient voltage surge suppressor (TVSS) is an appliance or device intended to protect electrical devices in alternating current (AC) circuits from voltage spikes with very short duration measured in microseconds, which can arise from a variety of causes including lightning strikes in the vicinity. A surge protector limits the voltage supplied to the electrical devices to a certain threshold by short-circuiting current to Ground (electricity), ground or absorbing the spike when a transient occurs, thus avoiding damage to the devices connected to it. Key specifications that characterize this device are the clamping voltage, or the transient voltage at which the device starts functioning, the Joule rating, a measure of how much energy can be absorbed per surge, and the response time. Definitions The terms ''surge protection device'' (''S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anode
An anode usually is an electrode of a polarized electrical device through which conventional current enters the device. This contrasts with a cathode, which is usually an electrode of the device through which conventional current leaves the device. A common mnemonic is ACID, for "anode current into device". The direction of conventional current (the flow of positive charges) in a circuit is opposite to the direction of electron flow, so (negatively charged) electrons flow from the anode of a galvanic cell, into an outside or external circuit connected to the cell. For example, the end of a household battery marked with a "+" is the cathode (while discharging). In both a galvanic cell and an electrolytic cell, the anode is the electrode at which the oxidation reaction occurs. In a galvanic cell the anode is the wire or plate having excess negative charge as a result of the oxidation reaction. In an electrolytic cell, the anode is the wire or plate upon which excess positive charge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zener Diode
A Zener diode is a type of diode designed to exploit the Zener effect to affect electric current to flow against the normal direction from anode to cathode, when the voltage across its terminals exceeds a certain characteristic threshold, the ''Zener voltage''. Zener diodes are manufactured with a variety of Zener voltages, including variable devices. Some types have an abrupt, heavily doped p–n junction with a low Zener voltage, in which case the reverse conduction occurs due to electron quantum tunnelling in the short distance between p and n regions. Diodes with a higher Zener voltage have more lightly doped junctions, causing their mode of operation to involve avalanche breakdown. Both breakdown types are present in Zener diodes with the Zener effect predominating at lower voltages and avalanche breakdown at higher voltages. Zener diodes are used to generate low-power stabilized supply rails from higher voltages and to provide reference voltages for circuits, especially sta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
