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DIAC Building February 2013
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] |
Passivity (engineering)
Passivity is a property of engineering systems, most commonly encountered in analog electronics and control systems. Typically, analog designers use ''passivity'' to refer to incrementally passive components and systems, which are incapable of Gain (electronics), power gain. In contrast, control systems engineers will use ''passivity'' to refer to thermodynamically passive ones, which consume, but do not produce, energy. As such, without context or a qualifier, the term ''passive'' is ambiguous. An electronic circuit consisting entirely of passive components is called a passive circuit, and has the same properties as a passive component. If a device is ''not'' passive, then it is an active device. Thermodynamic passivity In control systems and circuit network theory, a passive component or circuit is one that consumes energy, but does not produce energy. Under this methodology, voltage source, voltage and current sources are considered active, while resistors, capacitors, ind ... [...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] |
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] |
Fuse (electrical)
In electronics and electrical engineering, a fuse is an electrical safety device that operates to provide overcurrent protection of an electrical circuit. Its essential component is a metal wire or strip that melts when too much current flows through it, thereby stopping or interrupting the current. It is a sacrificial device; once a fuse has operated, it is an open circuit, and must be replaced or rewired, depending on its type. Fuses have been used as essential safety devices from the early days of electrical engineering. Today there are thousands of different fuse designs which have specific current and voltage ratings, breaking capacity, and response times, depending on the application. The time and current operating characteristics of fuses are chosen to provide adequate protection without needless interruption. Wiring regulations usually define a maximum fuse current rating for particular circuits. A fuse can be used to mitigate short circuits, overloading, mismatched loads ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crowbar (circuit)
A crowbar circuit is an electrical circuit used for preventing an overvoltage or surge condition of an AC power supply unit from damaging the circuits attached to the power supply. It operates by putting a short circuit or low resistance path across the voltage output (Vo), like dropping a Crowbar (tool), crowbar across the output terminals of the power supply. Crowbar circuits are frequently implemented using a thyristor, TRIAC, trisil or thyratron as the shorting device. Once triggered, they depend on the current (electricity), current-limiting circuitry of the power supply or, if that fails, the blowing of the line fuse (electrical), fuse or tripping the circuit breaker. The name is derived from having the same effect as throwing a crowbar over exposed power supply terminals to short the output. Example In the following example crowbar circuit, the LM431 adjustable Zener_diode, zener regulator controls the gate of the TRIAC. The Voltage_divider, resistor divider of R1 and R2 p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Varistor
A varistor (a.k.a. voltage-dependent resistor (VDR)) is a surge protecting electronic component with an electrical resistance that varies with the applied voltage. It has a nonlinear, non- ohmic current–voltage characteristic that is similar to that of a diode. Unlike a diode however, it has the same characteristic for both directions of traversing current. Traditionally, varistors were constructed by connecting two rectifiers, such as the copper-oxide or germanium-oxide rectifier in antiparallel configuration. At low voltage the varistor has a high electrical resistance which decreases as the voltage is raised. Modern varistors are primarily based on sintered ceramic metal-oxide materials which exhibit directional behavior only on a microscopic scale. This type is commonly known as the metal-oxide varistor (MOV). Varistors are used as control or compensation elements in circuits either to provide optimal operating conditions or to protect against excessive transient voltage ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Littelfuse
Littelfuse, Inc. is an American electronics manufacturing company headquartered in Chicago, Illinois. The company primarily produces circuit protection products (fuses) but also manufactures a variety of switches, automotive sensors and, through its subsidiary Zilog, microprocessors. Littelfuse was founded in 1927. In addition to its Chicago, Illinois, world headquarters, Littelfuse has more than 40 sales, distribution, manufacturing and engineering facilities in the Americas, Europe and Asia. Littelfuse is the developer of AutoFuse, the first blade-type automotive fuse. History Early history Edward V. Sundt founded Littelfuse in 1927 in Chicago Illinois as Littelfuse Laboratories. Prior to founding Littelfuse, Sundt had worked for General Electric and Stewart-Warner, where he found diagnostic equipment frequently experienced electrical failure. Sundt developed Littelfuse's first product, a small protective fuse, to regulate current in diagnostic equipment and prevent electrical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
STMicroelectronics
STMicroelectronics Naamloze vennootschap, NV (commonly referred to as ST or STMicro) is a European multinational corporation, multinational semiconductor contract manufacturing and design company. It is the largest of such companies in Europe. It was founded in 1987 from the merger of two state-owned semiconductor corporations: ''Thomson Semiconducteurs'' of United States/France and ''SGS Microelettronica'' of Italy. The company is incorporated in the Netherlands and headquartered in Plan-les-Ouates, Switzerland. Its shares are traded on Euronext Paris, the Borsa Italiana and the New York Stock Exchange. History ST was formed in 1987 by the merger of two government-owned semiconductor companies: Italian SGS Microelettronica (where SGS stands for ''Società Generale Semiconduttori'', "General Semiconductor Company"), and French ''Thomson Semiconducteurs'', the semiconductor arm of Thomson SA, Thomson. SGS Microelettronica originated in 1972 from a previous merger of two compan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trisil
Trisil is a trade name for a thyristor surge protection device, an electronic component designed to protect electronic circuits from overvoltage. Unlike a transient voltage suppression diodes, such as Transil, Trisil acts as a crowbar device, switching ON when the voltage across it exceeds its breakover voltage. Overview A Trisil is bidirectional, behaving the same way in both directions. It is principally a voltage-controlled triac without gate. The behavior of a Trisil is similar to a SIDAC, but unlike SIDAC, Trisil devices are commonly used to protect circuits from overvoltage.They act faster and can handle more current. In 1982, the only manufacturer was Thomson SA; a successor company, ST Microelectronics continues to make the devices. This type of crowbar protector is widely used to protect telecom equipment from lightning-induced transients and power line-induced currents. Other manufacturers of similar devices include Bourns (TISP) and Littelfuse (SIDACtor). Instead ... [...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] |
Relaxation Oscillator
In electronics, a relaxation oscillator is a nonlinear electronic oscillator circuit that produces a nonsinusoidal repetitive output signal, such as a triangle wave or square wave. on Peter Millet'Tubebookswebsite The circuit consists of a feedback loop containing a switching device such as a transistor, comparator, relay, op amp, or a negative resistance device like a tunnel diode, that repetitively charges a capacitor or inductor through a resistance until it reaches a threshold level, then discharges it again. The period of the oscillator depends on the time constant of the capacitor or inductor circuit. The active device switches abruptly between charging and discharging modes, and thus produces a discontinuously changing repetitive waveform. This contrasts with the other type of electronic oscillator, the harmonic or linear oscillator, which uses an amplifier with feedback to excite resonant oscillations in a resonator, producing a sine wave. Relaxation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
