What is a FET?

FET is a new type of semiconductor device with PN junction.

The control mechanism of FET is different from that of ordinary transistor, it is a voltage control device that uses the electric field effect to control the current of the pipe, so it is named field effect transistor ( represented by FET ). Compared with ordinary transistors, FET has the advantages of high input impedance, simple manufacturing process, small noise figure, good thermal stability and large dynamic range, it is particularly suitable for making large scale integrated circuits, which is widely used in high frequency, intermediate frequency, low frequency, direct current, switch and impedance transformation circuits.

First, the classification of field effect transistors

1 ) According to different materials, it can be divided into junction field effect transistor and insulated gate type ( MOS ) field effect transistor, the insulated gate type is also divided into depletion type and enhanced type.

2 ) Different semiconductor materials used in the channel can be divided into N-channel and P-channel field-effect transistors.

Second, the main parameters of field effect transistor

( 1 ) pinch off voltage U, generally speaking, when the reverse voltage between the gate source increases to a certain value no leakage current Ip exists regardless of the source voltage. This voltage that starts the Ip zero is called the pinch-off voltage.

( 2 ) the turn-on voltage Ur is generally speaking for MOS transistors, indicating the gate voltage value when Ip begins to appear. N-channel enhancement and P-channel depletion type Ur are positive and negative for N-channel depletion type and P-channel enhanced Ur.

( 3 ) When Ucs = 0 and Ups are large enough, the saturation value of leakage current is the saturation leakage current of the pipe, which is usually represented by IDSS.

( 4 ) The ratio of the drain voltage Ups and the leakage current Ip is known as the ratio of the drain voltage Ups and the leakage current Ip, which is called the common conductive resistance of the pipe, which is represented by the common symbol Ro.

( 5 ) Transconductance is an AC parameter of FET, which is a parameter that characterizes the control leakage current of gate voltage. It is equal to the small change of the gate voltage, in addition to the change of the corresponding leakage current, the unit is represented by the symbol GM.

This article is from Allicdata Electronics Limited. Reprinted need to indicate the source.

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