Transistor (basics knowledge and applications)

Hello guys,

we will be talking about a very important component in every electronics device, it makes a revolution in communications and we will use it in several projects.

The bipolar point-contact transistor was invented in December 1947 at the Bell Telephone Laboratories by John Bardeen and Walter Brattain under the direction of William Shockley. The junction version known as the bipolar junction transistor (BJT), invented by Shockley in 1948, was for three decades the device of choice in the design of discrete and integrated circuits.

I think you are Wondering why this component is very famous? How this transistor work?

A transistor as Amplifier:

Do you know the water tab? when you rotate it anti Clockwise by your finger the water will flow the more you rotate the more you get water.

What if you use water to rotate the tap instead of your fingers? The water will open the tap and water will flow too.

I know you are wondering about the benefits of making water flow by water it seems nonsense what if you make the tap fully opened with only one water drop?

That means you will use small drops to make a high-water flow.

The same happened in electrical current when you apply a small current it can be 1uA you will get a high current from the collector to the emitter can be 100mA so you amplified the signal.

What if close the tap 5 times from (base) the current will stop flowing 5 times too so your signal will get amplified by the same form such as audio devices and speakers.

Theoretical of work:

Bipolar Transistor or BJT comes in two basic forms. An NPN (Negative-Positive-Negative) type and a PNP (Positive-Negative-Positive) type.

The most commonly used transistor configuration is the NPN Transistor. the junctions of the bipolar transistor can be biased in one of three different ways – Common Base, Common Emitter and Common Collector use both electrons and electron holes as charge carriers. In contrast, a unipolar transistor, such as a field-effect transistor, uses only one kind of charge carrier. A bipolar transistor allows a small current injected at one of its terminals to control a much larger current flowing between two other terminals, making the device capable of amplification or switching.

BJTs use two junctions between two semiconductor types, n-type and p-type, which are regions in a single crystal of material. The junctions can be made in several different ways, such as changing the doping of the semiconductor material as it is grown, by depositing metal pellets to form alloy junctions, or by such methods as diffusion of n-type and p-type doping substances into the crystal. The superior predictability and performance of junction transistors soon displaced the original point-contact transistor. Diffused transistors, along with other components, are elements of integrated circuits for analog and digital functions. Hundreds of bipolar junction transistors can be made in one circuit at a very low cost.

So you can consider there are three boys playing ball the first will be N-type electrons the second will be P-type holes the third is N-type and the electron is the ball.

Now we need to close the circuit, which means current flow means electron go throw three junctions to allow current flow, the first player well give its ball (electron) to the second player (holes) and the second player give the ball to the third player (electron) the third player will give the ball to wire and the wire will give the ball to a battery to complete the circuit

All of that will happen if and only if a small current is applied on the base to begin playing with a ball

A transistor as a Switch:

You know from the odds that when you stop current flowing to base you will stop the collector Emitter flowing which is (Output), the benefit of this is that you can switch a high current 20A with a small current 10mA, another benefit you its electron-based switch so you can be closed and opened millions time per second.

That allowed you to make more complicated circuits such as logics gate by adding transistors together

AND, OR, Not, the three Brothers can make a lot of circuit together remember the transistor can be switched so fast and I will tell you the benefit later in this article

Flipflop circuit: the base of (volatile memory)

flip-flop or latch is a circuit that has two stable states. The circuit can be made to change state by signals applied to one or more control inputs and will have one or two outputs. It is the basic storage element in sequential logic. Flip-flops and latches are fundamental building blocks of digital electronics systems used in computers, communications, and many other types of systems, with to transistor you can make simple memory so you can store 0 or 1 because you can switch it on-of very fast you can put several latches (flip flops ) together make a register and several registers together make the ram.

with a logic gate you can make a calculator:

now you can use a calculator for summation or subtraction then store the result on register all that will be done in a few seconds, all of the programs work this way with more complicated operations all of the programs have instructions that converted to machine language according to ASCII code after converting your instruction to machine language the processor will execute your instruction buy doing arithmetic algebra on it then store it in memory so CPU & Ram made of transistor A lot of transistor millions of transistors make CPU calculate faster and store it in the memory faster.

Duo to all of that the transistor is very important for everything, Embedded system , smartphones , computer.

After inventing the BJT transistor sanctities want to make transistor more powerful faster
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Then they use CMOS technology to make Integrated ic, after knowing the basics of transistors we will make applications for transistors as switches & amplifiers too

feel free to ask me any question:


Facebook: Eng. Darwish Ali

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Excellent Eng! This is a very detailed information on how the transistor was created and how it works, will be very useful for the people who wants to know about the basics of electronics.

Thanks for the sharing!

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