FET-Field Effect Transistors-Introduction

jojo November 12, 2013 1 Comment
Introduction to FET-Field Effect Transistor So far we have discussed the circuit applications of ordinary transistors, in which both holes and electrons take part. This is the reason that these are sometimes called the bipolar transistors. Such transistors have two main drawbacks namely low input impedance because of forward biased emitter junction and considerable noise level. Both of these drawbacks have been overcome, to a great extent in the field effect transistor (FET), which is an electric field (or...
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Semiconductor diode fabrication types

jojo August 25, 2009 2 Comments
This blog post is continuation to the original post: Fabrication techniques of a P-N junction diode 1. Grown Junction Diode: Diodes of this type are formed during the crystal pulling process. P and N-type impurities can be alternately added to the molten semiconductor material in the crucible, which results in a P-N junction, as shown when crystal is pulled. After slicing, the larger area device can then be cut into a large number (say in thousands) of smaller-area semiconductor...
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Fabrication techniques of a P-N junction diode

jojo February 9, 2011 11 Comments
General Introduction to Fabrication techniques of a P-N junction diode: In practice, the P-N junction is formed from a single mono crystalline structure by adding carefully controlled amounts of donor and acceptor impurities. Here discussion is limited only to acquaintation with the basic techniques and terminology (not expertise in fabrication). The first and foremost requirement is to obtain an extremely pure germanium or silicon. Impurity of less than one part in ten billion (1010) is required for most semiconductor device...
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Photoconductive cells

jojo August 24, 2009 7 Comments
The photoconductive cell is a two terminal semiconductor device whose terminal resistance will vary (linearly) with the intensity of the inci­dent light. For obvious reasons, it is frequently called a photoresistive device. The photoconductive materials most frequently used include cadmium sulphide (CdS) and cadmium selenide (CdSe). Both materials respond rather slowly to changes in light intensity. The peak spectral response time of CdS units is about 100 ms and 10 ms for CdSe cells. Another im­portant difference between the...
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Optocoupler devices and application

jojo January 23, 2011 6 Comments
An optocoupler (or an optoelectronic coupler) is basically an interface between two circuits which operate at (usually) different voltage levels. The key advantage of an optocoupler is the electrical isolation between the input and output circuits. With an optocoupler, the only contact between the input and the output is a beam of light. Because of this it is possible to have an insulation resistance between the two circuits in the thousands of megohms. Isolation like this is useful in...
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LCD-Liquid Crystal Displays

jojo February 28, 2012 2 Comments
What is an LCD/Definition of Liquid Crystal Displays The liquid-crystal display has the distinct advantage of having a low power consumption than the LED. It is typically of the order of microwatts for the display in comparison to the some order of milliwatts for LEDs. Low power consumption requirement has made it compatible with MOS integrated logic circuit. Its other advantages are its low cost, and good contrast. The main drawbacks of LCDs are additional requirement of light source,...
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LDR-Light Dependent Resistors

jojo November 1, 2018 6 Comments
A Light Dependent Resistor (LDR) is also called a photoresistor or a cadmium sulfide (CdS) cell. It is also called a photoconductor. It is basically a photocell that works on the principle of photoconductivity. The passive component is basically a resistor whose resistance value decreases when the intensity of light decreases. This optoelectronic device is mostly used in light varying sensor circuit, and light and dark activated switching circuits. Some of its applications include camera light meters, street lights,...
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Semiconductor diodes and diode symbol

jojo July 21, 2018 4 Comments
You might have read about a “Diode” in many of your text books or electronics magazines/websites. But you still don’t get the concept? Don’t worry! In this article, we explain in detail about a semiconductor diode and its properties. Well, a diode is nothing but a PN junction. We have crafted two excellent articles about PN junction before in CircuitsToday. Please read our articles “Understanding PN Junction” and then move on to read “PN Junction Characteristics“. These two articles...
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Tunnel diode

jojo August 17, 2009 12 Comments
What is a tunnel diode? Dr.Leo Esaki invented a tunnel diode, which is also known as “Esaki diode” on behalf of its inventor. Its a high conductivity two terminal P-N junction diode doped heavily about 1000 times greater than a conventional junction diode. Because of heavy doping depletion layer width is reduced to an extremely small value of 1/10000 m. Reverse breakdown voltage is also reduced to very small value~0 resulting in appearance of the diode to be broken...
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Vacuum tube diodes

jojo August 17, 2009 No Comments
Vacuum Diodes-Applications and Construction The simplest form of the electron tube for the production and control of free electrons is a Vacuum diode. Two electrodes are there for a vacuum diode known as anode and cathode. Cathode serves as an emitter of electrons where as anode serves as a collector of electrons. Cathode may be a simple filament of tungsten or thoriated tungsten. It can also be a nickel tube coated with barium oxide or strontium oxide. Oxide coated...
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