What are transistors and how do they work?

No other technology has had such a profound impact on human civilization as the advent of the transistor. A processor is the brain of a smartphone. And this CPU has about 2 billion transistors. What are the functions of these tiny devices?

Transistor 

How do transistors work?

Transistors may function as a switch. They can amplify a weak signal; in fact, amplification is a transistor's primary purpose. Let's start with the fundamentals of transistors. We'll return to the application section later. Semiconductors, such as silicon and germanium, are used in transistors. Each silicon atom is connected to four other silicon atoms via four bonds. Silicon's valence electron has four electrons. Let's substitute a four-handed smiley for the silicon atom. One electron is held in each hand. Each of these electrons will be shared with a silicon atom in the vicinity. 

A covalent bond is what this is called. The electrons are currently in their valence band. If pure silicon is required for electrical conductivity, To become free electrons, the electrons must absorb some energy. Pure silicon, as a result, has poor electrical conductivity.

Doping is a method for increasing the conductivity of semiconductors. Let's assume you inject five valence electrons into phosphorous. N-type doping is the term for this. If you inject three valence electrons into the boron, however, there will be an empty place for one electron. A hole is an empty place that can be filled at any time by a nearby electron. The flow of electrons is represented by holes traveling in the opposite direction. This is referred to as P-type doping.

A transistor is created by doping a silicon wafer in the following manner. However, if you truly want to understand how a transistor works, you must first grasp what happens at the electron level in a more fundamental component, a diode. When one portion of silicon is doped as P-type and the other portion is doped as N-type, a diode is produced. At the intersection of the N and P joints, something really fascinating happens. The numerous electrons on the inside will naturally gravitate to the holes on the P side. As a result, the P side border will be slightly negatively charged, whereas the N side boundary will be slightly positively charged.

If you connect an external power source to the diode as demonstrated, the electrons and holes will be attracted to the power source. In this situation, electricity flow is impossible. The scenario is completely different if you reverse the power connection. Assume the power source has sufficient voltage to break through the potential barrier. The electrons will be driven away by the negative terminal, as you can see. The electrons will be drained of energy when they pass the potential barrier and will easily fill the holes in the P region. However, due to the positive terminal's attraction, these electrons can now jump to neighboring holes in the P region.

and makes its way through the external circuit. This is referred to as a diode's undefined forward biassing. Keep this simple diode idea in mind, and you'll have no trouble understanding how a transistor works. Returning to the transistor now. It's worth noting that the P-layer is quite thin and just weakly doped. A transistor is basically two diodes placed back to back, as you can see. So, regardless of how the power supply is connected, one diode will always be reverse biassed and impede the flow of energy. This indicates that the transistor is turned off. Now, as indicated, attach a second power supply. The power source should be able to overcome the potential barrier with enough voltage.

So this is just a diode with a forward bias. As a result, the N area will emit a large number of electrons. A few electrons join with the holes, jump across the surrounding holes, and flow to the base, much as in a diode. However, a large number of electrons have crossed to the P side. What will happen to the remaining electrons? Consider this for a moment. The positive terminal of the first power source will attract the remaining electrons, which will flow straight as indicated. It's worth noting that the P area is rather small, ensuring that no leftover electrons travel to the second power source's positive terminal. In other words, a low base current is amplified into a large collector current.

The type of electron flow is simply connected with the name of the transistor terminal. The collector current will rise proportionately if the base current is increased. This is a classic example of current amplification in action. A bipolar junction transistor is the type of transistor we've been discussing. Let's swap out this fake transistor for an actual one. By adding another transistor, you may increase the amplification even more. This transistor's base is linked to the first transistor's emitter. When a weak fluctuating signal is introduced at the input, such as that found in a microphone, the signal is amplified at the loudspeaker. Another remarkable feature of this simple circuit is that the transistor may be turned on or off based on the value of the supplied voltage. In this case, the transistor serves as a switch. The transistor's property allows access to the worlds of digital electronics and digital memory. Two BJTs may construct the fundamental dynamic memory element of a computer: A pair of flip-flops 

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