Miyerkules, Nobyembre 4, 2015

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TRANSISTOR



I.                    Introduction

It is amazing to know how our brain works. It could do multiple tasks for every single second of our life. Because of its very complex work, it comprises billions of brain cells which are known as neurons. In the world of technology, computers are associated to our brain in which behind its operation is also billions of electrical components that work together. These are resistors, capacitors and transistors. Since we have learned already about the first two electrical components, we will now study about transistors.
Transistor is a three-leg electrical component that makes it unique from the rest. It functions as an amplifier or a switch.  It is a bipolar junction which consists of three layers of doped semiconductor which is usually made of silicon and is even considered as the fundamental composition of integrated circuit.

II.                  Parts

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As mentioned earlier, a transistor has three legs. To understand the function of the three legs, let’s associate it with a faucet. In a faucet, there is the path where water enters and leaves though it is somehow just a one path. As observe in the faucet, there is a valve that controls the volume of water that will flow.

III.                    Types

A.      Bipolar Junction Transistor

This is a type of transistor having 3 legs or regions known as the base, the collector, and the emitter. Unlike FET transistors, the other type, this transistor is a current-controlled device because small current that enters in the base region of it can cause a tremendous increase of current flowing from the emitter to the collector region. This is the only transistor that is turned on by inputting current in the base because of its low impedance or resistance. This is also the reason why BJT can amplify the most.
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A.1. Types of Bipolar Junction Transistor

a. NPN. This is a transistor that has two n-type semiconductors, the collector and the emitter, with p-type semiconductor as the base separating them. The electrons are the major current carrier of this transistor.


b. PNP. This is the opposite of NPN. This consists of two p-type semiconductors and one n-type separating the two. In this type, the electrons are the minority current carrier. Hence, the holes are the major current carrier of it.
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B.      Field Effect Transistor

1. a. JFET has lesser impedance than MOSFET.
1. b. MOSFET has higher impedance than JFET.

This has other names of its three legs or regions which are gate, source and drain. If BJTs are current-controlled devices, FETs, on the other way around are voltage-controlled devices. It means that a voltage applied in the gate controls the flow of current from the source to the drain regions. FETs have high impedance causing little current through it making it to produce less amplification than the BJT. But the good thing here is it can cause less loading in the circuit compared to BJT and they are considered to be cheaper and easy to make.

      
                   C.      Other types according to Function

C.1. Small Signal Transistors are preferable to use in amplifying low-level signals which also functions as switches.


C.2. Small Switching Transistors are primarily made as switches but can also be used as amplifiers but not as capable as the small signal transistor.

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C.3. Power Transistors are best used when large values of current and voltage are used. These come in NPN and PNP forms.

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IV.                    Functions

1.       Amplifier. Small amount of current enters to one leg and as it leaves, it becomes bigger current. In other words, it multiplies the input current. In this case, common applications are hearing aids, microphone and speakers.

2.       Binary switch. Same manner in amplification where small amount of current flows in one part and it becomes bigger as it flows to the other part. These small current will switch on the bigger one. So in a microchip, billions of transistors can be switched on and off and these san store two numbers, zero for off and one for on. All transistors can store different numbers or letters individually that are known as characters.


V.                  References

Retrieved on October 31, 2015 at http://whatis.techtarget.com/definition/transistor
Retrieved on October 31, 2015 at http://www.technologystudent.com/elec1/transis1.htm
Retrieved on October 31, 2015 at http://boysdad.com/archives/3633







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