Transistor was a breakthrough invention in the development of human civilization, there is no device in modern electronics that does not have transistor.

Even in the device through which you are reading this post, there are hundreds of billions of transistors, then you understand that the importance of transistors cannot be overstated. Because there are transistors in every modern technology from the surface to the space.

What is the transistor in today's post? And how it works is explained in a very simple way. Hope you read the post carefully and the whole thing will be clear to you.

The components that you can see in the above picture are basically transistors and each transistor usually has three terminals.

Electricity comes through one, electricity goes out through one, and terminal number three controls this coming and going. These three terminals of the transistor are called collector, base and emitter and each transistor has a model number. If you search Google with this model number, you will get detailed information about this transistor ie, at what voltage does the transistor work? How much current can go through it? What is the base voltage? What is the collector voltage? You will get all the information about each subject.

Transistors are generally of two types

1. Bipolar Junction Transistor (BJT)

• NPN Transistor
• PNP Transistor

2. Field Effect Transistor (FET)

However, although their names or categories are different, their work is the same and that is switching and amplifying the signal, that is, one of the functions of a transistor is to turn on and off a load like a switch, but a transistor is not like a switch. Transistors can turn a load on or off from several thousand to hundreds of thousands of times per second. But another function of the transistor is to amplify the weak signal like when we speak in the microphone it is heard slowly but it is heard very loud in the speaker then this sound is amplified by the transistor.

Today we will talk about BJT transistor (Bipolar Junction Transistor) because BJT can be called the basis of transistor. If you understand BJT then you can understand rest categories of transistor.

NPN Transistor is called NPN Transistor which has N type means Negative semiconductor on both sides and P type means Positive semiconductor in the middle.

Transistor which has P type means Positive semiconductor on both sides and N type means Negative semiconductor in the middle is called PNP Transistor.

In the figure below we have shown the symbols of NPN and PNP transistors.

In the case of NPN, this arrow mark is on the outside, that is, the current comes through the collector and goes to the ground or negative through the emitter.

In the case of PNP, this arrow is inward, ie current comes through the emitter and goes through the collector to ground or negative.

Now we will know how transistor works.

Look at the above diagram and think that the diagram with EBC terminal is an NPN transistor. There is a door in the middle of the figure connecting the EBC terminal and it is normally closed. The light will turn on when the current from the positive of the battery goes through the load and the transistor to the negative, completing the circuit. But then because the door is closed the current cannot pass due to which the light is off. So to open this gate a positive voltage is applied to the base of the NPN transistor but a small current is applied to the base of the transistor (minimum 0.7 V - 6 V). However, different transistors may have different base voltages.

In the above diagram circuit we have used a 12V battery so we have used a resistor to limit the current. When I switched on the buzzer current, current flowed through the load and pushed the buzzer's closed door open, causing the current to flow and the light to turn on.

Now if we turn off the base current switch then the door will close as the current is no longer flowing so the light will not light. So here I understood that the load can be turned on and off by controlling the base of the transistor.

However, in case of BJT transistor, the more the base current can be increased, the more current passes through the transistor.

However, a question may come to your mind, why is there a need to make so many stories to run the lights with a 12 volt battery? You manually turn on the switches of your house and turn on the load. In short, transistors are used for automatic switching with volts, so transistors are needed for automatic switching of 12 volt loads. I hope you understand.

In the case of NPN transistor, the positive connection of the battery with the collector of the transistor and the negative or ground connection with the emitter have to be given. And when a positive voltage is applied to the NPN transistor, the transistor turns on.

In the case of PNP transistor, the positive connection of the battery with the emitter of the transistor and the negative or ground connection with the collector have to be given. And when negative voltage is applied to NPN transistor, the transistor turns on.

That is, if there is N in the battery, then negative supply should be provided here.

And if there is P in the bell then positive supply has to be given here.

If you are working with microcontroller or sensor then transistor is definitely required because you can never turn on any big load with the output of microcontroller or sensor.

Hope you understand what transistor is, its types and how it works.

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