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Guidance: Field effect transistor (FET) is abbreviated as field effect transistor. Generally, transistors are conductive by two kinds of polar carriers, i.e. most carriers and a few negative carriers. Therefore, they are called bipolar transistors, while FET is conductive only by most carriers. It is opposite to bipolar transistors, it is also called unipolar transistors.
Field Effect Transistor(FET)
Field effect transistors are referred to as FET. Generally, transistors are conductive by two kinds of polar carriers, i.e. most carriers and a few negative carriers. Therefore, they are called bipolar transistors, while FET is conductive only by most carriers. It is opposite to bipolar transistors, it is also called unipolar transistors. It belongs to voltage-controlled semiconductor devices. It has the advantages of high input resistance (108-109_), low noise, low power consumption, large dynamic range, easy integration, no secondary breakdown, wide safe working area, etc. It has become a strong competitor of bipolar transistors and power transistors.
Different from ordinary three-stage transistors, FET belongs to voltage control device. Its tube current is controlled by gate voltage, which is similar to the characteristics of electronic transistors.
Types of Field Effect Transistor
According to the difference of channel semiconductor materials, the junction type and insulating gate type are divided into two kinds: channel and P channel. According to the conductive mode, FETs can be divided into depletion type and enhancement type. The junction FETs are both depletion type. The insulated gate FETs have both depletion type and enhancement type. Field effect transistors can be divided into junction field effect transistors and MOS field effect transistors. MOSFETs can be divided into four types: N-channel depletion type and enhanced type, P-channel depletion type and enhanced type.
Type Naming Method
There are two current naming methods. The first naming method is the same as bipolar triode. The third letter J stands for junction field effect transistor, and the third letter O stands for insulated gate field effect transistor. The second letter represents the material, D is P-type silicon, the inversion layer is N-channel, and C is N-type silicon P-channel. For example, 3DJ6D is a junction N-channel field effect transistor and 3DO6C is an insulated gate N-channel field effect transistor. The second naming method is CS *, CS stands for field effect transistors, * numbers for models, and letters for different specifications in the same model. For example, CS14A, CS45G, etc.
Parameters of FET
There are many parameters of FETs, including DC parameters, AC parameters and limit parameters, but in general, the following main parameters are concerned in use:
- IDSS-saturated leakage current. It refers to the leakage current when the grid voltage UGS = 0 in the junction or depletion insulated gate FET.
- The triode of UP working in switching state can be called switching transistor. Triode has PNP, NPN, single junction transistor, etc.