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RECTIFIERS

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                                             Rectifier:       It is a device which converts a.c. voltage to d.c. voltage by allowing a current to flow through it in one direction.       It is classified into 2 types:       (i) Half Wave Rectifier(H.W.R)       (ii)Full Wave Rectifier(F.W.R)   (i) HALF WAVE RECTIFIER :        It is a simple rectifier made with one diode. When the voltage of the alternating current is positive, the diode becomes forward-biased and current flows through it. When the voltage is negative, the diode is reverse-biased and the current stops.Hence, the output wave form of H.W.R has only 1 half cycle and the remaining half cycle is blocked.      As a result, nearly half of the applied power is wasted in half wave rectifier. In addition to this, the output current or  voltage produced by half wave rectifier is not a pure DC but a pulsating DC which is not much useful. (a)RMS ( Root mean squared) value of current:                 
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LIGHT EMITTING DIODE

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In our phones, our cars and even our homes. Any time something electronic lights up, there’s a good chance that an LED is behind it. They come in a huge variety of sizes, shapes, and colors, but no matter what they look like they have one thing in common: they’re the bacon of electronics. They’re widely purported to make any project better and they’re often added to unlikely things. LEDs are a particular type of diode that convert electrical energy into light. In fact, LED stands for “Light Emitting Diode” .And this is reflected in the similarity between the diode and LED schematic symbols: A light-emitting diode (LED) is a two-leadsemiconductors light source. It is a p-n junction diode that emits light when activated. When a suitable voltage is applied to the leads, electrons are able to recombine with electron hole within the device, releasing energy in the form of photons. A P-N junction can convert absorbed light energy into a proportional electric current. The same p
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PHOTODIODE & SOLAR CELL

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Photodiode A photodiode is a special type of junction diode used for detecting optical signals. It is a reverse biased p-n junction made from a photosensitive material.In photodiode,current carriers are generated by photons through photo excitation.Its symbol is Construction A photodiode is fabricated with a transparent cover to allow light to fall on the diode and operated under reverse bias. Working When the photodiode is illuminated with light (photons),with energy greater than the energy gap of the semiconductor,then electron-hole pairs are generated due to the absorption of photons. These charge carriers contribute to the reverse current. V-I Characteristics Its V-I characteristics are shown in figure.We observe from the figure that current in photodiode changes with the change in light intensity(I) when reverse bias is applied. Solar cell Solar cell is a p-n junction diode,which converts solar energy into electr
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Introduction to Semiconductors

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WHAT IS A SEMICONDUCTOR? Materials whose conductivity lies between those of conductors and insulators are called semiconductors. The most commonly used semiconductors are germanium(Ge) and silicon(Si).                                                                                                 (google images)                                                                CONDUCTION OF SEMICONDUCTORS The conductivity and resistivity of materials depends mainly on the energy gap between conduction band and valence band.                                                                                                (google images) For conductors there is no electron gap and hence conduction band and valence band overlap each other. If large potential difference is applied across the valence band, then electrons jump into conduction band and hence conduct electrons.   For silicon and germanium 1.1eV and 0.71eV needs to be applied for ele
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