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MOS transistor

MOS transistor

Introduction to the product description: 1. In a triode, both holes and free electrons participate in conduction, which is called a bipolar device, denoted by BJT; while a field effect transistor has only multiple electrons, it is called a unipolar device, denoted by FET. Since the polyton concentration is not affected by external temperature, light, or radiation, it is more appropriate to choose FET under conditions of drastic environmental changes. This is the reason why we usually call FETs relatively stable. 2. When working in the amplified state, the transistor's emission junction is forward biased and has a base current, which is a current control device. The corresponding input resistance is small, about 103Ω; when the FET is working in the amplified state, there is no gate current and is a voltage control device. The input resistance is very large, the input resistance of the JFET is greater than 107Ω, and the input resistance of the MOS tube is greater than 109Ω.

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product description:

1. In a triode, both holes and free electrons participate in conduction, which is called a bipolar device, which is represented by BJT; while a field effect tube has only multi-child conduction, which is called a unipolar device, which is represented by FET. Because of the multi-subconcentration It is not affected by external temperature, light, or radiation, and it is more appropriate to choose FET under the conditions of severe environmental changes. This is the reason why we usually call the field effect tube more stable.

2. When working in the amplified state, the transistor's emission junction is forward biased and has a base current, which is a current control device. The corresponding input resistance is small, about 103Ω; when the FET is working in the amplified state, there is no gate current and is a voltage control device. The input resistance is very large, the input resistance of the JFET is greater than 107Ω, and the input resistance of the MOS tube is greater than 109Ω.

3. The source and drain of the field effect tube are symmetrical in structure and can be used interchangeably (but it should be noted that sometimes the manufacturer has already shorted the source and substrate of the MOS tube in the tube and cannot be interchanged during use) The VGS of the depletion type MOS tube can be positive, negative, or zero, and it is more flexible in use. The collector and emitter of the triode generally cannot be used interchangeably.

Fourth, when working under low voltage and low current conditions, FET can be used as a voltage-controlled variable linear resistor and a non-contact electronic switch with small on-resistance.


5. The MOS tube has simple process, low power consumption, and is suitable for large-scale integration. The triode has high gain, low nonlinear distortion, and stable performance. In discrete component circuits and medium and small-scale integrated circuits, triodes still dominate.

Sixth, the transfer characteristics of the triode (ic-vbe relationship) change according to the exponential law, and the transfer characteristics of the field effect tube change according to the square law, so the nonlinear distortion of the field effect tube is larger than the nonlinear distortion of the triode.

Seven, the three basic configuration circuits of the field effect tube (common source, common drain and common gate) can be compared with the common emission, common collection and common base circuits of the triode. Since the gate of the field effect tube has no current, the input resistance R'i≈∞. The transconductance gm is one order of magnitude smaller than that of the triode, and we can use the transfer characteristics to obtain the derivative


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