DatasheetLib – A new Datasheet Database Website to revolutionize Datasheet Discovery

Electrical engineers all over the world would bet anything for a better datasheet search engine. Its such an under served  market that there are still rooms for improvement. Although there are hundreds of websites which supplies datasheets in the form of PDF like DatasheetCatalogue, AllDataSheet and many others, recently launched DatasheetLib follows a different approach from the existing players. In this article my aim is to compare different datasheet providing websites and see how they all are different from each other. Analyzing the Home Page Let’s just begin by comparing the home page of above 3 datasheet providers. Our aim…

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Fluke 233 Remote Display Multimeter

Remote Display Multimeter Fluke 233. Using the Fluke233 remote digital thermometer you can work at two places in same time.Such a multimeter is very in suitable performing test and measurements at hazardous environments.Standing on ladders, tangling long test cables, calling a second guy for at the desired location and perform the test/measurement from a convenient place through the detachable wireless display module.The Fluke 233 is a gadget that will surely make your work much easier. Old price: 311.95$ , New price: 279.99$. 10% discount, you save $31.56.  Click here and grab the offer! The fluke233  is packed with a lot of…

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Characteristics of a UJT

UJT Characteristics The static emitter char­acteristic (a curve showing the relation between emitter voltage VE and emitter current IE) of a UJT at a given inter base voltage VBB is shown in figure.  From figure it is noted that for emitter potentials to the left of peak point, emitter current IE never exceeds IEo . The current IEo corresponds very closely to the reverse leakage current ICo of the conventional BJT. This region, as shown in the figure, is called the cut-off region. Once con­duction is established at VE = VP the emitter po­tential VE starts decreasing with the increase…

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UJT-Uni Junction Transistors

Unijunction transistor (abbreviated as UJT), also called the double-base diode is a 2-layer, 3-terminal solid-state (silicon) switching device. The device has-a unique characteristic that when it is triggered, its emitter current increases re generatively (due to negative resistance characteristic) until it is restricted by emitter power supply. The low cost per unit, combined with its unique characteristic, have warranted its use in a wide variety of applications. A few include oscillators, pulse generators, saw-tooth generators, triggering circuits, phase control, timing circuits, and voltage-or current-regulated supplies. The device is in general, a low-power-absorbing device under normal operating conditions and provides tremendous…

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LASCR-Light Activated SCR

Light activated SCR (LASCR) or a Photo SCR  is just an ordinary SCR except that it can also be light triggered. Most LASCRs also have a gate terminal for being triggered by an elec­trical pulse just as a conventional SCR. The basic construction of an LASCR is shown in figure. The schematic symbols most commonly used for the LASCR are shown in figure.  Some LASCRs have clear windows in their cases so that light sources from other devices can be cou­pled to them. Many have the light source encapsu­lated in the same package so that a relay is formed. When…

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Gate Turn Off Switch

Gate turn-off switch (GTO) is, like an SCR, is a four layer, three junction semiconductor device with three external terminals, namely, the anode, the cathode and the gate, as illustrated in figure. The basic construction, schematic symbol of a GTO are shown is figures  respectively.  Although the graphic symbol is different from either the SCR or the SCS, the transistor equivalent is exactly the same and the characteristics are similar. The main advantage of the GTO over the SCR or SCS is that it can be turned on or off by applying the proper pulse to the cathode gate (without…

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Silicon Unilateral Switch

The diac and the silicon bilateral switch are grouped as bilateral or bidirectional devices because they can breakover in either direction. There are also breakover devices which breakover in only one direction; they fall in the category of unilateral or unidirectional breakover devices. Although unilateral breakover devices are more frequently employed in SCR triggering, they can also be employed in triac triggering circuit if they have some extra supporting circuitry. Silicon unilateral switch (SUS) is one of the important unilat­eral breakover devices. V-I characteristic of SUS The schematic symbol and V-I characteristic of SUS are shown is figure a and…

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Silicon Bilateral Switch

Silicon bilateral switch (SBS) is another breakover device which is capable of triggering triacs, and it is popular in low-voltage trigger control circuits. They have breakover voltages lower than those for diacs, ± 8 V being the most popular rating. V-I characteristic curve of an SBS is similar to that of the diac, but it has more pronounced “negative resistance” region i.e., its decline in voltage is more drastic after it enters the conducting state. The schematic symbol and V-I characteristic of an SBS are shown in figure a and b respectively. When SBS switches into conducting state the voltage…

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Shockley Diode

To know more on the invention and history of the device click on this link - Shockley Diode – Invention History The four-layer diode, also called the Shockley diode after its inventor William Shockley, is essentially a low-current SCR without a gate. It is classified as a diode because it has only two external terminals through anode and cathode. Because of its four doped regions it is often called a P-N-P-N diode. The basic structure, two transistor version, equivalent tran­sistor circuit and schematic symbol of a Shockley diode are shown in figure. Shockley Diode Symbol The easiest way to understand how…

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SCS-Silicon Controlled Switch

Silicon controlled switch (SCS), like the SCR, is a unilateral, four layer three junction P-N-P-N silicon device with four electrodes namely cathode C, cathode gate Gx, anode gate G2 and the anode A, as shown in figure. Infact, the SCS is a low power device compared with the SCR. It handles currents in milli amperes rather than amperes. SCS differs from an SCR in the following aspects. It has an additional gate—the anode gate.It is physically smaller than SCR.It has smaller leakage and holding currents than SCR.It needs small triggering signals. It gives more uniform triggering characteristics from sample to…

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