Field effect transistor (FET) is a new type of semiconductor device with PN junction. The control mechanism of FET is different from ordinary transistors. It is a kind of voltage control device which uses electric field effect to control pipeline current, so it is called field effect transistor (FET). Compared with ordinary transistors, field effect transistors have the advantages of high input impedance, simple fabrication process, low noise coefficient, good thermal stability and large dynamic range. They are especially suitable for manufacturing large-scale integrated circuits and are widely used in high-frequency, interconnected and other occasions. Intermediate frequency, low frequency, DC, switch and impedance conversion circuits. The appearance of the public field effect transistor is shown in Fig.
First, the classification of FET.
According to the different materials, it can be divided into junction field effect transistor and insulated gate type (MOS) field effect transistor, and insulated gate type can be divided into depletion type and enhancement type.
Different semiconductor materials used in the channel can be divided into N channel and P channel field-effect transistor. Secondly, the main parameter of the field effect transistor, the clamping voltage U, generally speaking, when the reverse voltage between the grid sources increases to a certain value, no matter what the source voltage, there is no leakage current Ip. The voltage to start IP zero is called pinch off voltage.
The conduction voltage Ur is usually used in MOS transistors to indicate the gate voltage at the beginning of Ip. N- channel enhanced and P- channel depletion Ur are negatively correlated to N- channel depletion and P- channel enhanced Ur.
When Ucs = 0 and Ups are large enough, the saturation of leakage current is the saturated leakage current of the pipeline, usually expressed by IDSS.
The ratio of drain voltage up s to drain current IP is called the ratio of drain voltage up s to drain current ip. It is called the common conductive resistance of the pipe and is represented by the common symbol Ro.
Transconductance is the AC parameter of FET. It is a parameter to characterize gate voltage control leakage current. It is equal to a slight change in gate voltage, except for the corresponding change in leakage current, the unit is Siemens, which is represented by the symbol GM.
Model naming method of field effect transistor
The first method is the same as bipolar transistors. The first letter denotes the number of electrodes, expressed in 3; the second letter denotes the material, D is the P-type silicon N channel, C is the N-type silicon P channel; the third letter denotes the junction field effect transistor, 0 is the insulated gate fIELD effect transistor.