The role of FETs - the "identity" of the 818 FET

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Introduction: What is the role of the FET ? Is it only in the circuit as a FET ? The answer is no. Just as we exist in this society, not only the children of the parents, the parents of the children, but also the multiple identities of classmates, colleagues, friends, etc., as well as the FET , then we will come to the 818 effect tube. What "identity" is it~~~

First, the role of FET - - Introduction

Field Effect Transistor (FET) is a common voltage-controlled semiconductor device because it is only conductive by a majority of carriers, so it is also called a unipolar FET. It has the advantages of high input impedance, low power consumption, large dynamic range, simple manufacturing process and easy integration. It has been widely used.

The FET is similar to a transistor and is a non-linear, controllable three-terminal device, thus enabling the role of a transistor in the circuit, such as: acting as an amplifier, acting as an impedance transformer, and acting as a variable resistor. , used as a constant current source, used as an electronic switch, etc., as detailed below:

Second, the role of the field effect tube - - used as an amplification tube

One of the functions of the field effect transistor is that it can be used as an amplification tube. The FET is similar to a triode, but because of its high input impedance and small coupling capacitor capacity, it can realize the function of the amplification tube without using a large-capacity Electrolytic capacitor as a coupling capacitor.

Third, the role of the field effect transistor II - used as impedance transformation

The second function of the FET is to be used as an impedance transformation. Since the FET has a relatively high input impedance, it is often used as an impedance conversion device in the input stage of the multistage amplifier.

Fourth, the role of the FET three - - used as a variable resistor

The third function of the FET is to be used as a variable resistor.

Fifth, the role of the FET four - - used as a constant current source

The fourth function of the FET is to be used as a constant current source.

Six, the role of the field effect tube five - - used as an electronic switch

The fifth function of the FET is to be used as an electronic switch. Since the FET is a voltage-controlled device with a large input impedance and high speed, it is suitable for a circuit with a small input current and is generally used as a switching transistor.

Extended reading

Field Effect Transistor - Comparison with Bipolar Transistors

As a unipolar transistor, the FET has the following characteristics compared with a bipolar transistor:

Feature 1: The FET is a voltage-controlled device that controls the drain current through the gate voltage.

Characteristic 2: The input current of the FET is small, which makes the input resistance large;

Feature 3: The FET is used as a unipolar transistor, which uses most carriers to conduct electricity and has good temperature stability.

Characteristic 4: Compared with the triode, the FET of the amplifier circuit is smaller;

Feature 5: The FET has a strong anti-radiation capability;

Feature 6: There is no shot noise in the FET, so the overall noise is small.

Recommended knowledge of the role of FETs:

1, FET working principle is also crazy

2. FET amplification circuit

3. Characteristics and applications of FET

4, FET use precautions and testing techniques

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