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Guide: Transistors , just a general term for all semiconductor-based components, then the question is, what is the working principle of the transistor ? Let's take a look at the bipolar transistor and field effect transistor as an example. ~

First, the working principle of the transistor - - Introduction

Transistor, the English name is transistor, refers to all single components based on semiconductor materials, such as diodes, transistors, FETs and so on. The transistor has various functions such as rectification, detection, amplification, voltage regulation, and switching. It has the characteristics of fast response and high precision. It is the basic building block for standardizing the operation of modern electronic circuits such as mobile phones and tablets. It has been widely used.

Second, the working principle of the transistor - - classification

Transistors are generic to all semiconductor devices and contain more than N classes, so they also come in many different ways. Transistors can be divided into silicon material transistors and germanium material transistors according to different materials used; they can be divided into NPN type transistors and PNP type transistors according to different polarities; they can be divided into diffusion type transistors and alloy type transistors according to different structures and manufacturing processes. And planar transistors; they can also be classified into different types according to different current capacities, different operating frequencies, and different package structures. But the transistor multi-finger transistor is mainly divided into bipolar transistor (BJT) and field effect transistor (FET). Next, we will use BJT and FET as an example to describe the working principle of the transistor.

Third, the working principle of the transistor - - bipolar transistor

The bipolar transistor, English name Bipolar Transistor, is the abbreviation for bipolar junction transistor. Because it has three terminals, we usually call it a triode. The triode is formed by two PN structures, which are divided into an emitter region, a base region, and a collector region, and correspondingly generate three electrodes: an emitter, a base, and a collector.

The working principle of the triode is sauce purple. First, the power supply acts on the emitter junction to make the emitter junction forward biased. The free electrons in the emitter region continuously flow to the base region to form an emitter current. Second, the free electrons flow from the emitter region to the base region. After that, it first gathers near the emitter junction, but with the increase of free electrons here, an electron concentration difference is formed inside the base region, so that free electrons gradually flow from the emitter junction to the collector junction in the base region to form a collector current; Finally, due to the large reverse voltage at the collector junction, the free electrons in the collector region are prevented from diffusing into the base region, and the free electrons collected near the collector junction are attracted to the collector region to form a collector current. .

Fourth, the working principle of the transistor - field effect transistor

The field effect transistor, English name is Field Effect Transistor, referred to as FET, is a device that controls the output loop current by controlling the electric field effect of the input loop. Can be divided into junction and insulated gate, enhanced and depletion, N-channel and P-channel, then we use N-channel junction field effect transistor as an example to illustrate the working principle of FET .

Corresponding to the base, collector and emitter of the triode, the FETs are the gate, the drain and the source, respectively. A negative voltage is applied between the gate and the source, and a forward voltage is applied between the drain and the source to ensure that the field effect transistor can work normally. The larger the applied negative voltage, the thicker the depletion region formed at the PN junction, the narrower the conduction channel, the larger the channel resistance, and the smaller the drain current; conversely, the smaller the applied negative voltage, the PN The thinner the depletion region formed by the junction, the thicker the conductive channel, the smaller the channel resistance, and the larger the drain current. Thus, the control of the channel current is completed by controlling the negative voltage applied between the gate and the source.

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