Transistor......

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Transistors

The name transistor comes from the phrase \transferring an electrical signal across a

resistor".

Transistors are active components and are found everywhere in electronic circuits. They are used as amplifiers and switching devices. As amplifiers, they are used in high and low frequency stages, oscillators, modulators, detectors and in any circuit needing to perform a function. In digital circuits they are used as switches. 

There is a large number of manufacturers around the world who produce semiconductors (transistors are members of this family of components), so there are literally thousands of different types. There are low, medium and high power transistors, for working with high and low frequencies, for working with very high current and/or high voltages.

The most common type of transistor is called bipolar and these are divided into NPN and PNP types.

Their construction-material is most commonly silicon (their marking has the letter B) or germanium (their marking has the letter A). Original transistor were made from germanium, but they were very temperature-sensitive. Silicon transistors are much more temperature-tolerant and much cheaper to manufacture.

 Transistors are manufactured in different shapes but they have three leads (legs). 

The BASE - which is the lead responsible for activating the transistor.
The COLLECTOR - which is the positive lead.
The EMITTER - which is the negative lead.

Bipolar transistors have three leads: for base (B), emitter (E), and for collector (C). Sometimes, HF transistors have another lead which is connected to the metal housing. This lead is connected to the ground of the circuit, to protect the transistor from possible external electrical interference. Four leads emerge from some other types, such as two-gate FETs. High power transistors are different from low-to-medium power, both in size and in shape.

Biasing Of Transistotr...

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Diode...

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Diode is basically a 2 lead semiconductor in simple way a diode is semiconductor what has 2 lead. In operation, the diode is just like one way gate for the flow of electrons. It is the main property of the diode that it allows current to pass in only one direction. 

asic Symbol of Diode As:

Now the next concept is how diode works. To understand this. So, let start the next and very important concept of diode working:

How Diode Works:

After the brief introduction of the diode, now I tell you the basic ideas about its working principles. When we refer to diode work, two main points to be remembered are in which diode works normally. They are Forward Bias Diode and Reverse Bias Diode. Now here I tell you about the both properties of diode working accordingly.

Forward Bias Diode:

When the diode is connected to the battery in the way as shown in below figure, then what happen are electrons from the N-Side and Holes from the P-Side are forced towards the center by the electrical field supplied by the battery. Due to the combination of electrons and holes, the current pass through the diode. When a diode is arranged in this way as shown below, it is called the Forwards Biased Diode.

I hope your concept about the forward biasing working of diode will be very clear , now let come to the second property of diode working, that is Reverse Biasing.

Reverse Bias Diode:

When the diode is connected to the circuit or battery as shown in below figure, then what happens is , holes in the N-side are forced to the left while electrons in the P-side are forced to the right. This process results in an empty zone around the PN – Junction that is free of any charge carrier creating a Depletion Region. This depletion region acts like an insulator which prevents the current from flowing through the diode. When a diode is arranged in this manner, then it Is called Reverse Biased diode.

Points about the working Principle of Diode:

1.      As stated earlier that the diode is just like one way gate, so it does not work all the time.

2.      For silicon diode, an applied voltage of 0.6 V or greater needed, otherwise the diode conduction will not occur and diode will not work.

This feature is useful in forming a voltage-sensitive switch

PN Junction Diode:

A PN Junction diode is formed by joining the n-type and p-type silicon. In practice, as the n-type (Silicon) Si crystal is being grown, the process is abruptly altered to grow p-type Si crystal. Finally, a glass or plastic coating is placed around the joined crystal.

The P side of the PN Junction diode is called anode and the N Side is called the Cathode of the PN Junction Diode. When the anode and cathode of a PN-junction diode are connected to external voltage such that the potential at anode is higher than the potential at cathode, the diode is said to be forward biased.

In a forward-biased diode current is allowed to flow through the device.

Reverse Biased Diode:

When potential at anode is smaller than the potential at cathode, the diode is said to be reverse biased. In a reverse-biased diode current is blocked.

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WHAT IS STEPPER MOTOR

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The Stepper   motor consist     of  a    permanent    magnetic rotating   shaft   is  called  the rotor,    and electromagnets on the stationary portion that surrounds the motor, called the stator. Figure 1  complete rotation of a stepper motor. At position  , we can see that the   rotor is   beginning at the   upper electromagnet, which is currently active (has voltage applied to it). To move the rotor clockwise (CW), the upper  electromagnet is deactivated and the right electromagnet is activated, causing the rotor to move 90 degrees  Clock Wise CW, aligning itself with the active magnet.  Process        is  repeated  in  the   same manner at the south and west    electromagnets until we once again reach the starting positions

clik here to see

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